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SYSTEMD.EXEC(5) systemd.exec SYSTEMD.EXEC(5)
systemd.exec - Execution environment configuration
service.service, socket.socket, mount.mount, swap.swap
Unit configuration files for services, sockets, mount points, and
swap devices share a subset of configuration options which define
the execution environment of spawned processes.
This man page lists the configuration options shared by these
four unit types. See systemd.unit(5) for the common options of
all unit configuration files, and systemd.service(5),
systemd.socket(5), systemd.swap(5), and systemd.mount(5) for more
information on the specific unit configuration files. The
execution specific configuration options are configured in the
[Service], [Socket], [Mount], or [Swap] sections, depending on
the unit type.
In addition, options which control resources through Linux
Control Groups (cgroups) are listed in
systemd.resource-control(5). Those options complement options
listed here.
A few execution parameters result in additional, automatic
dependencies to be added:
• Units with WorkingDirectory=, RootDirectory=, RootImage=,
RuntimeDirectory=, StateDirectory=, CacheDirectory=,
LogsDirectory= or ConfigurationDirectory= set automatically
gain dependencies of type Requires= and After= on all mount
units required to access the specified paths. This is
equivalent to having them listed explicitly in
RequiresMountsFor=.
• Similarly, units with PrivateTmp= enabled automatically get
mount unit dependencies for all mounts required to access
/tmp/ and /var/tmp/. They will also gain an automatic After=
dependency on systemd-tmpfiles-setup.service(8).
• Units whose standard output or error output is connected to
journal or kmsg (or their combinations with console output,
see below) automatically acquire dependencies of type After=
on systemd-journald.socket.
• Units using LogNamespace= will automatically gain ordering
and requirement dependencies on the two socket units
associated with systemd-journald@.service instances.
The following settings may be used to change a service's view of
the filesystem. Please note that the paths must be absolute and
must not contain a ".." path component.
ExecSearchPath=
Takes a colon separated list of absolute paths relative to
which the executable used by the Exec*= (e.g. ExecStart=,
ExecStop=, etc.) properties can be found. ExecSearchPath=
overrides $PATH if $PATH is not supplied by the user through
Environment=, EnvironmentFile= or PassEnvironment=. Assigning
an empty string removes previous assignments and setting
ExecSearchPath= to a value multiple times will append to the
previous setting.
Added in version 250.
WorkingDirectory=
Takes a directory path relative to the service's root
directory specified by RootDirectory=, or the special value
"~". Sets the working directory for executed processes. If
set to "~", the home directory of the user specified in User=
is used. If not set, defaults to the root directory when
systemd is running as a system instance and the respective
user's home directory if run as user. If the setting is
prefixed with the "-" character, a missing working directory
is not considered fatal. If RootDirectory=/RootImage= is not
set, then WorkingDirectory= is relative to the root of the
system running the service manager. Note that setting this
parameter might result in additional dependencies to be added
to the unit (see above).
RootDirectory=
Takes a directory path relative to the host's root directory
(i.e. the root of the system running the service manager).
Sets the root directory for executed processes, with the
pivot_root(2) or chroot(2) system call. If this is used, it
must be ensured that the process binary and all its auxiliary
files are available in the new root. Note that setting this
parameter might result in additional dependencies to be added
to the unit (see above).
The MountAPIVFS= and PrivateUsers= settings are particularly
useful in conjunction with RootDirectory=. For details, see
below.
If RootDirectory=/RootImage= are used together with
NotifyAccess= the notification socket is automatically
mounted from the host into the root environment, to ensure
the notification interface can work correctly.
Note that services using RootDirectory=/RootImage= will not
be able to log via the syslog or journal protocols to the
host logging infrastructure, unless the relevant sockets are
mounted from the host, specifically:
The host's os-release(5) file will be made available for the
service (read-only) as /run/host/os-release. It will be
updated automatically on soft reboot (see:
systemd-soft-reboot.service(8)), in case the service is
configured to survive it.
Example 1. Mounting logging sockets into root environment
BindReadOnlyPaths=/dev/log /run/systemd/journal/socket /run/systemd/journal/stdout
In place of the directory path a ".v/" versioned directory
may be specified, see systemd.v(7) for details.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
RootImage=
Takes a path to a block device node or regular file as
argument. This call is similar to RootDirectory= however
mounts a file system hierarchy from a block device node or
loopback file instead of a directory. The device node or file
system image file needs to contain a file system without a
partition table, or a file system within an MBR/MS-DOS or GPT
partition table with only a single Linux-compatible
partition, or a set of file systems within a GPT partition
table that follows the Discoverable Partitions
Specification[1].
When DevicePolicy= is set to "closed" or "strict", or set to
"auto" and DeviceAllow= is set, then this setting adds
/dev/loop-control with rw mode, "block-loop" and
"block-blkext" with rwm mode to DeviceAllow=. See
systemd.resource-control(5) for the details about
DevicePolicy= or DeviceAllow=. Also, see PrivateDevices=
below, as it may change the setting of DevicePolicy=.
Units making use of RootImage= automatically gain an After=
dependency on systemd-udevd.service.
The host's os-release(5) file will be made available for the
service (read-only) as /run/host/os-release. It will be
updated automatically on soft reboot (see:
systemd-soft-reboot.service(8)), in case the service is
configured to survive it.
In place of the image path a ".v/" versioned directory may be
specified, see systemd.v(7) for details.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
Added in version 233.
RootImageOptions=
Takes a comma-separated list of mount options that will be
used on disk images specified by RootImage=. Optionally a
partition name can be prefixed, followed by colon, in case
the image has multiple partitions, otherwise partition name
"root" is implied. Options for multiple partitions can be
specified in a single line with space separators. Assigning
an empty string removes previous assignments. Duplicated
options are ignored. For a list of valid mount options,
please refer to mount(8).
Valid partition names follow the Discoverable Partitions
Specification[1]: root, usr, home, srv, esp, xbootldr, tmp,
var.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
Added in version 247.
RootEphemeral=
Takes a boolean argument. If enabled, executed processes will
run in an ephemeral copy of the root directory or root image.
The ephemeral copy is placed in
/var/lib/systemd/ephemeral-trees/ while the service is active
and is cleaned up when the service is stopped or restarted.
If RootDirectory= is used and the root directory is a
subvolume, the ephemeral copy will be created by making a
snapshot of the subvolume.
To make sure making ephemeral copies can be made efficiently,
the root directory or root image should be located on the
same filesystem as /var/lib/systemd/ephemeral-trees/. When
using RootEphemeral= with root directories, btrfs(5) should
be used as the filesystem and the root directory should
ideally be a subvolume which systemd can snapshot to make the
ephemeral copy. For root images, a filesystem with support
for reflinks should be used to ensure an efficient ephemeral
copy.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
Added in version 254.
RootHash=
Takes a data integrity (dm-verity) root hash specified in
hexadecimal, or the path to a file containing a root hash in
ASCII hexadecimal format. This option enables data integrity
checks using dm-verity, if the used image contains the
appropriate integrity data (see above) or if RootVerity= is
used. The specified hash must match the root hash of
integrity data, and is usually at least 256 bits (and hence
64 formatted hexadecimal characters) long (in case of SHA256
for example). If this option is not specified, but the image
file carries the "user.verity.roothash" extended file
attribute (see xattr(7)), then the root hash is read from it,
also as formatted hexadecimal characters. If the extended
file attribute is not found (or is not supported by the
underlying file system), but a file with the .roothash suffix
is found next to the image file, bearing otherwise the same
name (except if the image has the .raw suffix, in which case
the root hash file must not have it in its name), the root
hash is read from it and automatically used, also as
formatted hexadecimal characters.
If the disk image contains a separate /usr/ partition it may
also be Verity protected, in which case the root hash may
configured via an extended attribute "user.verity.usrhash" or
a .usrhash file adjacent to the disk image. There's currently
no option to configure the root hash for the /usr/ file
system via the unit file directly.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
Added in version 246.
RootHashSignature=
Takes a PKCS7 signature of the RootHash= option as a path to
a DER-encoded signature file, or as an ASCII base64 string
encoding of a DER-encoded signature prefixed by "base64:".
The dm-verity volume will only be opened if the signature of
the root hash is valid and signed by a public key present in
the kernel keyring. If this option is not specified, but a
file with the .roothash.p7s suffix is found next to the image
file, bearing otherwise the same name (except if the image
has the .raw suffix, in which case the signature file must
not have it in its name), the signature is read from it and
automatically used.
If the disk image contains a separate /usr/ partition it may
also be Verity protected, in which case the signature for the
root hash may configured via a .usrhash.p7s file adjacent to
the disk image. There's currently no option to configure the
root hash signature for the /usr/ via the unit file directly.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
Added in version 246.
RootVerity=
Takes the path to a data integrity (dm-verity) file. This
option enables data integrity checks using dm-verity, if
RootImage= is used and a root-hash is passed and if the used
image itself does not contain the integrity data. The
integrity data must be matched by the root hash. If this
option is not specified, but a file with the .verity suffix
is found next to the image file, bearing otherwise the same
name (except if the image has the .raw suffix, in which case
the verity data file must not have it in its name), the
verity data is read from it and automatically used.
This option is supported only for disk images that contain a
single file system, without an enveloping partition table.
Images that contain a GPT partition table should instead
include both root file system and matching Verity data in the
same image, implementing the Discoverable Partitions
Specification[1].
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
Added in version 246.
RootImagePolicy=, MountImagePolicy=, ExtensionImagePolicy=
Takes an image policy string as per systemd.image-policy(7)
to use when mounting the disk images (DDI) specified in
RootImage=, MountImage=, ExtensionImage=, respectively. If
not specified the following policy string is the default for
RootImagePolicy= and MountImagePolicy:
root=verity+signed+encrypted+unprotected+absent: \
usr=verity+signed+encrypted+unprotected+absent: \
home=encrypted+unprotected+absent: \
srv=encrypted+unprotected+absent: \
tmp=encrypted+unprotected+absent: \
var=encrypted+unprotected+absent
The default policy for ExtensionImagePolicy= is:
root=verity+signed+encrypted+unprotected+absent: \
usr=verity+signed+encrypted+unprotected+absent
Added in version 254.
MountAPIVFS=
Takes a boolean argument. If on, a private mount namespace
for the unit's processes is created and the API file systems
/proc/, /sys/, /dev/ and /run/ (as an empty "tmpfs") are
mounted inside of it, unless they are already mounted. Note
that this option has no effect unless used in conjunction
with RootDirectory=/RootImage= as these four mounts are
generally mounted in the host anyway, and unless the root
directory is changed, the private mount namespace will be a
1:1 copy of the host's, and include these four mounts. Note
that the /dev/ file system of the host is bind mounted if
this option is used without PrivateDevices=. To run the
service with a private, minimal version of /dev/, combine
this option with PrivateDevices=.
In order to allow propagating mounts at runtime in a safe
manner, /run/systemd/propagate/ on the host will be used to
set up new mounts, and /run/host/incoming/ in the private
namespace will be used as an intermediate step to store them
before being moved to the final mount point.
Added in version 233.
ProtectProc=
Takes one of "noaccess", "invisible", "ptraceable" or
"default" (which it defaults to). When set, this controls the
"hidepid=" mount option of the "procfs" instance for the unit
that controls which directories with process metainformation
(/proc/PID) are visible and accessible: when set to
"noaccess" the ability to access most of other users' process
metadata in /proc/ is taken away for processes of the
service. When set to "invisible" processes owned by other
users are hidden from /proc/. If "ptraceable" all processes
that cannot be ptrace()'ed by a process are hidden to it. If
"default" no restrictions on /proc/ access or visibility are
made. For further details see The /proc Filesystem[2]. It is
generally recommended to run most system services with this
option set to "invisible". This option is implemented via
file system namespacing, and thus cannot be used with
services that shall be able to install mount points in the
host file system hierarchy. Note that the root user is
unaffected by this option, so to be effective it has to be
used together with User= or DynamicUser=yes, and also without
the "CAP_SYS_PTRACE" capability, which also allows a process
to bypass this feature. It cannot be used for services that
need to access metainformation about other users' processes.
This option implies MountAPIVFS=.
If the kernel doesn't support per-mount point hidepid= mount
options this setting remains without effect, and the unit's
processes will be able to access and see other process as if
the option was not used.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
Added in version 247.
ProcSubset=
Takes one of "all" (the default) and "pid". If "pid", all
files and directories not directly associated with process
management and introspection are made invisible in the /proc/
file system configured for the unit's processes. This
controls the "subset=" mount option of the "procfs" instance
for the unit. For further details see The /proc
Filesystem[2]. Note that Linux exposes various kernel APIs
via /proc/, which are made unavailable with this setting.
Since these APIs are used frequently this option is useful
only in a few, specific cases, and is not suitable for most
non-trivial programs.
Much like ProtectProc= above, this is implemented via file
system mount namespacing, and hence the same restrictions
apply: it is only available to system services, it disables
mount propagation to the host mount table, and it implies
MountAPIVFS=. Also, like ProtectProc= this setting is
gracefully disabled if the used kernel does not support the
"subset=" mount option of "procfs".
Added in version 247.
BindPaths=, BindReadOnlyPaths=
Configures unit-specific bind mounts. A bind mount makes a
particular file or directory available at an additional place
in the unit's view of the file system. Any bind mounts
created with this option are specific to the unit, and are
not visible in the host's mount table. This option expects a
whitespace separated list of bind mount definitions. Each
definition consists of a colon-separated triple of source
path, destination path and option string, where the latter
two are optional. If only a source path is specified the
source and destination is taken to be the same. The option
string may be either "rbind" or "norbind" for configuring a
recursive or non-recursive bind mount. If the destination
path is omitted, the option string must be omitted too. Each
bind mount definition may be prefixed with "-", in which case
it will be ignored when its source path does not exist.
BindPaths= creates regular writable bind mounts (unless the
source file system mount is already marked read-only), while
BindReadOnlyPaths= creates read-only bind mounts. These
settings may be used more than once, each usage appends to
the unit's list of bind mounts. If the empty string is
assigned to either of these two options the entire list of
bind mounts defined prior to this is reset. Note that in this
case both read-only and regular bind mounts are reset,
regardless which of the two settings is used.
Using this option implies that a mount namespace is allocated
for the unit, i.e. it implies the effect of PrivateMounts=
(see below).
This option is particularly useful when
RootDirectory=/RootImage= is used. In this case the source
path refers to a path on the host file system, while the
destination path refers to a path below the root directory of
the unit.
Note that the destination directory must exist or systemd
must be able to create it. Thus, it is not possible to use
those options for mount points nested underneath paths
specified in InaccessiblePaths=, or under /home/ and other
protected directories if ProtectHome=yes is specified.
TemporaryFileSystem= with ":ro" or ProtectHome=tmpfs should
be used instead.
Added in version 233.
MountImages=
This setting is similar to RootImage= in that it mounts a
file system hierarchy from a block device node or loopback
file, but the destination directory can be specified as well
as mount options. This option expects a whitespace separated
list of mount definitions. Each definition consists of a
colon-separated tuple of source path and destination
definitions, optionally followed by another colon and a list
of mount options.
Mount options may be defined as a single comma-separated list
of options, in which case they will be implicitly applied to
the root partition on the image, or a series of
colon-separated tuples of partition name and mount options.
Valid partition names and mount options are the same as for
RootImageOptions= setting described above.
Each mount definition may be prefixed with "-", in which case
it will be ignored when its source path does not exist. The
source argument is a path to a block device node or regular
file. If source or destination contain a ":", it needs to be
escaped as "\:". The device node or file system image file
needs to follow the same rules as specified for RootImage=.
Any mounts created with this option are specific to the unit,
and are not visible in the host's mount table.
These settings may be used more than once, each usage appends
to the unit's list of mount paths. If the empty string is
assigned, the entire list of mount paths defined prior to
this is reset.
Note that the destination directory must exist or systemd
must be able to create it. Thus, it is not possible to use
those options for mount points nested underneath paths
specified in InaccessiblePaths=, or under /home/ and other
protected directories if ProtectHome=yes is specified.
When DevicePolicy= is set to "closed" or "strict", or set to
"auto" and DeviceAllow= is set, then this setting adds
/dev/loop-control with rw mode, "block-loop" and
"block-blkext" with rwm mode to DeviceAllow=. See
systemd.resource-control(5) for the details about
DevicePolicy= or DeviceAllow=. Also, see PrivateDevices=
below, as it may change the setting of DevicePolicy=.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
Added in version 247.
ExtensionImages=
This setting is similar to MountImages= in that it mounts a
file system hierarchy from a block device node or loopback
file, but instead of providing a destination path, an overlay
will be set up. This option expects a whitespace separated
list of mount definitions. Each definition consists of a
source path, optionally followed by a colon and a list of
mount options.
A read-only OverlayFS will be set up on top of /usr/ and
/opt/ hierarchies for sysext images and /etc/ hierarchy for
confext images. The order in which the images are listed will
determine the order in which the overlay is laid down: images
specified first to last will result in overlayfs layers
bottom to top.
Mount options may be defined as a single comma-separated list
of options, in which case they will be implicitly applied to
the root partition on the image, or a series of
colon-separated tuples of partition name and mount options.
Valid partition names and mount options are the same as for
RootImageOptions= setting described above.
Each mount definition may be prefixed with "-", in which case
it will be ignored when its source path does not exist. The
source argument is a path to a block device node or regular
file. If the source path contains a ":", it needs to be
escaped as "\:". The device node or file system image file
needs to follow the same rules as specified for RootImage=.
Any mounts created with this option are specific to the unit,
and are not visible in the host's mount table.
These settings may be used more than once, each usage appends
to the unit's list of image paths. If the empty string is
assigned, the entire list of mount paths defined prior to
this is reset.
Each sysext image must carry a
/usr/lib/extension-release.d/extension-release.IMAGE file
while each confext image must carry a
/etc/extension-release.d/extension-release.IMAGE file, with
the appropriate metadata which matches
RootImage=/RootDirectory= or the host. See: os-release(5). To
disable the safety check that the extension-release file name
matches the image file name, the
x-systemd.relax-extension-release-check mount option may be
appended.
When DevicePolicy= is set to "closed" or "strict", or set to
"auto" and DeviceAllow= is set, then this setting adds
/dev/loop-control with rw mode, "block-loop" and
"block-blkext" with rwm mode to DeviceAllow=. See
systemd.resource-control(5) for the details about
DevicePolicy= or DeviceAllow=. Also, see PrivateDevices=
below, as it may change the setting of DevicePolicy=.
In place of the image path a ".v/" versioned directory may be
specified, see systemd.v(7) for details.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
Added in version 248.
ExtensionDirectories=
This setting is similar to BindReadOnlyPaths= in that it
mounts a file system hierarchy from a directory, but instead
of providing a destination path, an overlay will be set up.
This option expects a whitespace separated list of source
directories.
A read-only OverlayFS will be set up on top of /usr/ and
/opt/ hierarchies for sysext images and /etc/ hierarchy for
confext images. The order in which the directories are listed
will determine the order in which the overlay is laid down:
directories specified first to last will result in overlayfs
layers bottom to top.
Each directory listed in ExtensionDirectories= may be
prefixed with "-", in which case it will be ignored when its
source path does not exist. Any mounts created with this
option are specific to the unit, and are not visible in the
host's mount table.
These settings may be used more than once, each usage appends
to the unit's list of directories paths. If the empty string
is assigned, the entire list of mount paths defined prior to
this is reset.
Each sysext directory must contain a
/usr/lib/extension-release.d/extension-release.IMAGE file
while each confext directory must carry a
/etc/extension-release.d/extension-release.IMAGE file, with
the appropriate metadata which matches
RootImage=/RootDirectory= or the host. See: os-release(5).
Note that usage from user units requires overlayfs support in
unprivileged user namespaces, which was first introduced in
kernel v5.11.
In place of the directory path a ".v/" versioned directory
may be specified, see systemd.v(7) for details.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
Added in version 251.
These options are only available for system services and are not
supported for services running in per-user instances of the
service manager.
User=, Group=
Set the UNIX user or group that the processes are executed
as, respectively. Takes a single user or group name, or a
numeric ID as argument. For system services (services run by
the system service manager, i.e. managed by PID 1) and for
user services of the root user (services managed by root's
instance of systemd --user), the default is "root", but User=
may be used to specify a different user. For user services of
any other user, switching user identity is not permitted,
hence the only valid setting is the same user the user's
service manager is running as. If no group is set, the
default group of the user is used. This setting does not
affect commands whose command line is prefixed with "+".
Note that this enforces only weak restrictions on the
user/group name syntax, but will generate warnings in many
cases where user/group names do not adhere to the following
rules: the specified name should consist only of the
characters a-z, A-Z, 0-9, "_" and "-", except for the first
character which must be one of a-z, A-Z and "_" (i.e. digits
and "-" are not permitted as first character). The user/group
name must have at least one character, and at most 31. These
restrictions are made in order to avoid ambiguities and to
ensure user/group names and unit files remain portable among
Linux systems. For further details on the names accepted and
the names warned about see User/Group Name Syntax[3].
When used in conjunction with DynamicUser= the user/group
name specified is dynamically allocated at the time the
service is started, and released at the time the service is
stopped — unless it is already allocated statically (see
below). If DynamicUser= is not used the specified user and
group must have been created statically in the user database
no later than the moment the service is started, for example
using the sysusers.d(5) facility, which is applied at boot or
package install time. If the user does not exist by then
program invocation will fail.
If the User= setting is used the supplementary group list is
initialized from the specified user's default group list, as
defined in the system's user and group database. Additional
groups may be configured through the SupplementaryGroups=
setting (see below).
DynamicUser=
Takes a boolean parameter. If set, a UNIX user and group pair
is allocated dynamically when the unit is started, and
released as soon as it is stopped. The user and group will
not be added to /etc/passwd or /etc/group, but are managed
transiently during runtime. The nss-systemd(8) glibc NSS
module provides integration of these dynamic users/groups
into the system's user and group databases. The user and
group name to use may be configured via User= and Group= (see
above). If these options are not used and dynamic user/group
allocation is enabled for a unit, the name of the dynamic
user/group is implicitly derived from the unit name. If the
unit name without the type suffix qualifies as valid user
name it is used directly, otherwise a name incorporating a
hash of it is used. If a statically allocated user or group
of the configured name already exists, it is used and no
dynamic user/group is allocated. Note that if User= is
specified and the static group with the name exists, then it
is required that the static user with the name already
exists. Similarly, if Group= is specified and the static user
with the name exists, then it is required that the static
group with the name already exists. Dynamic users/groups are
allocated from the UID/GID range 61184...65519. It is
recommended to avoid this range for regular system or login
users. At any point in time each UID/GID from this range is
only assigned to zero or one dynamically allocated
users/groups in use. However, UID/GIDs are recycled after a
unit is terminated. Care should be taken that any processes
running as part of a unit for which dynamic users/groups are
enabled do not leave files or directories owned by these
users/groups around, as a different unit might get the same
UID/GID assigned later on, and thus gain access to these
files or directories. If DynamicUser= is enabled, RemoveIPC=
and PrivateTmp= are implied (and cannot be turned off). This
ensures that the lifetime of IPC objects and temporary files
created by the executed processes is bound to the runtime of
the service, and hence the lifetime of the dynamic
user/group. Since /tmp/ and /var/tmp/ are usually the only
world-writable directories on a system this ensures that a
unit making use of dynamic user/group allocation cannot leave
files around after unit termination. Furthermore
NoNewPrivileges= and RestrictSUIDSGID= are implicitly enabled
(and cannot be disabled), to ensure that processes invoked
cannot take benefit or create SUID/SGID files or directories.
Moreover ProtectSystem=strict and ProtectHome=read-only are
implied, thus prohibiting the service to write to arbitrary
file system locations. In order to allow the service to write
to certain directories, they have to be allow-listed using
ReadWritePaths=, but care must be taken so that UID/GID
recycling doesn't create security issues involving files
created by the service. Use RuntimeDirectory= (see below) in
order to assign a writable runtime directory to a service,
owned by the dynamic user/group and removed automatically
when the unit is terminated. Use StateDirectory=,
CacheDirectory= and LogsDirectory= in order to assign a set
of writable directories for specific purposes to the service
in a way that they are protected from vulnerabilities due to
UID reuse (see below). If this option is enabled, care should
be taken that the unit's processes do not get access to
directories outside of these explicitly configured and
managed ones. Specifically, do not use BindPaths= and be
careful with AF_UNIX file descriptor passing for directory
file descriptors, as this would permit processes to create
files or directories owned by the dynamic user/group that are
not subject to the lifecycle and access guarantees of the
service. Note that this option is currently incompatible with
D-Bus policies, thus a service using this option may
currently not allocate a D-Bus service name (note that this
does not affect calling into other D-Bus services). Defaults
to off.
Added in version 232.
SupplementaryGroups=
Sets the supplementary Unix groups the processes are executed
as. This takes a space-separated list of group names or IDs.
This option may be specified more than once, in which case
all listed groups are set as supplementary groups. When the
empty string is assigned, the list of supplementary groups is
reset, and all assignments prior to this one will have no
effect. In any way, this option does not override, but
extends the list of supplementary groups configured in the
system group database for the user. This does not affect
commands prefixed with "+".
SetLoginEnvironment=
Takes a boolean parameter that controls whether to set the
$HOME, $LOGNAME, and $SHELL environment variables. If not
set, this defaults to true if User=, DynamicUser= or PAMName=
are set, false otherwise. If set to true, the variables will
always be set for system services, i.e. even when the default
user "root" is used. If set to false, the mentioned variables
are not set by the service manager, no matter whether User=,
DynamicUser=, or PAMName= are used or not. This option
normally has no effect on services of the per-user service
manager, since in that case these variables are typically
inherited from user manager's own environment anyway.
Added in version 255.
PAMName=
Sets the PAM service name to set up a session as. If set, the
executed process will be registered as a PAM session under
the specified service name. This is only useful in
conjunction with the User= setting, and is otherwise ignored.
If not set, no PAM session will be opened for the executed
processes. See pam(8) for details.
Note that for each unit making use of this option a PAM
session handler process will be maintained as part of the
unit and stays around as long as the unit is active, to
ensure that appropriate actions can be taken when the unit
and hence the PAM session terminates. This process is named
"(sd-pam)" and is an immediate child process of the unit's
main process.
Note that when this option is used for a unit it is very
likely (depending on PAM configuration) that the main unit
process will be migrated to its own session scope unit when
it is activated. This process will hence be associated with
two units: the unit it was originally started from (and for
which PAMName= was configured), and the session scope unit.
Any child processes of that process will however be
associated with the session scope unit only. This has
implications when used in combination with NotifyAccess=all,
as these child processes will not be able to affect changes
in the original unit through notification messages. These
messages will be considered belonging to the session scope
unit and not the original unit. It is hence not recommended
to use PAMName= in combination with NotifyAccess=all.
These options are only available for system services, or for
services running in per-user instances of the service manager in
which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the kernel
via the "kernel.unprivileged_userns_clone=" sysctl).
CapabilityBoundingSet=
Controls which capabilities to include in the capability
bounding set for the executed process. See capabilities(7)
for details. Takes a whitespace-separated list of capability
names, e.g. CAP_SYS_ADMIN, CAP_DAC_OVERRIDE, CAP_SYS_PTRACE.
Capabilities listed will be included in the bounding set, all
others are removed. If the list of capabilities is prefixed
with "~", all but the listed capabilities will be included,
the effect of the assignment inverted. Note that this option
also affects the respective capabilities in the effective,
permitted and inheritable capability sets. If this option is
not used, the capability bounding set is not modified on
process execution, hence no limits on the capabilities of the
process are enforced. This option may appear more than once,
in which case the bounding sets are merged by OR, or by AND
if the lines are prefixed with "~" (see below). If the empty
string is assigned to this option, the bounding set is reset
to the empty capability set, and all prior settings have no
effect. If set to "~" (without any further argument), the
bounding set is reset to the full set of available
capabilities, also undoing any previous settings. This does
not affect commands prefixed with "+".
Use systemd-analyze(1)'s capability command to retrieve a
list of capabilities defined on the local system.
Example: if a unit has the following,
CapabilityBoundingSet=CAP_A CAP_B
CapabilityBoundingSet=CAP_B CAP_C
then CAP_A, CAP_B, and CAP_C are set. If the second line is
prefixed with "~", e.g.,
CapabilityBoundingSet=CAP_A CAP_B
CapabilityBoundingSet=~CAP_B CAP_C
then, only CAP_A is set.
AmbientCapabilities=
Controls which capabilities to include in the ambient
capability set for the executed process. Takes a
whitespace-separated list of capability names, e.g.
CAP_SYS_ADMIN, CAP_DAC_OVERRIDE, CAP_SYS_PTRACE. This option
may appear more than once, in which case the ambient
capability sets are merged (see the above examples in
CapabilityBoundingSet=). If the list of capabilities is
prefixed with "~", all but the listed capabilities will be
included, the effect of the assignment inverted. If the empty
string is assigned to this option, the ambient capability set
is reset to the empty capability set, and all prior settings
have no effect. If set to "~" (without any further argument),
the ambient capability set is reset to the full set of
available capabilities, also undoing any previous settings.
Note that adding capabilities to the ambient capability set
adds them to the process's inherited capability set.
Ambient capability sets are useful if you want to execute a
process as a non-privileged user but still want to give it
some capabilities. Note that in this case option keep-caps is
automatically added to SecureBits= to retain the capabilities
over the user change. AmbientCapabilities= does not affect
commands prefixed with "+".
Added in version 229.
NoNewPrivileges=
Takes a boolean argument. If true, ensures that the service
process and all its children can never gain new privileges
through execve() (e.g. via setuid or setgid bits, or
filesystem capabilities). This is the simplest and most
effective way to ensure that a process and its children can
never elevate privileges again. Defaults to false. In case
the service will be run in a new mount namespace anyway and
SELinux is disabled, all file systems are mounted with
MS_NOSUID flag. Also see No New Privileges Flag[4].
Note that this setting only has an effect on the unit's
processes themselves (or any processes directly or indirectly
forked off them). It has no effect on processes potentially
invoked on request of them through tools such as at(1),
crontab(1), systemd-run(1), or arbitrary IPC services.
Added in version 187.
SecureBits=
Controls the secure bits set for the executed process. Takes
a space-separated combination of options from the following
list: keep-caps, keep-caps-locked, no-setuid-fixup,
no-setuid-fixup-locked, noroot, and noroot-locked. This
option may appear more than once, in which case the secure
bits are ORed. If the empty string is assigned to this
option, the bits are reset to 0. This does not affect
commands prefixed with "+". See capabilities(7) for details.
These options are only available for system services and are not
supported for services running in per-user instances of the
service manager.
SELinuxContext=
Set the SELinux security context of the executed process. If
set, this will override the automated domain transition.
However, the policy still needs to authorize the transition.
This directive is ignored if SELinux is disabled. If prefixed
by "-", failing to set the SELinux security context will be
ignored, but it's still possible that the subsequent execve()
may fail if the policy doesn't allow the transition for the
non-overridden context. This does not affect commands
prefixed with "+". See setexeccon(3) for details.
Added in version 209.
AppArmorProfile=
Takes a profile name as argument. The process executed by the
unit will switch to this profile when started. Profiles must
already be loaded in the kernel, or the unit will fail. If
prefixed by "-", all errors will be ignored. This setting has
no effect if AppArmor is not enabled. This setting does not
affect commands prefixed with "+".
Added in version 210.
SmackProcessLabel=
Takes a SMACK64 security label as argument. The process
executed by the unit will be started under this label and
SMACK will decide whether the process is allowed to run or
not, based on it. The process will continue to run under the
label specified here unless the executable has its own
SMACK64EXEC label, in which case the process will transition
to run under that label. When not specified, the label that
systemd is running under is used. This directive is ignored
if SMACK is disabled.
The value may be prefixed by "-", in which case all errors
will be ignored. An empty value may be specified to unset
previous assignments. This does not affect commands prefixed
with "+".
Added in version 218.
LimitCPU=, LimitFSIZE=, LimitDATA=, LimitSTACK=, LimitCORE=,
LimitRSS=, LimitNOFILE=, LimitAS=, LimitNPROC=, LimitMEMLOCK=,
LimitLOCKS=, LimitSIGPENDING=, LimitMSGQUEUE=, LimitNICE=,
LimitRTPRIO=, LimitRTTIME=
Set soft and hard limits on various resources for executed
processes. See setrlimit(2) for details on the process
resource limit concept. Process resource limits may be
specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as
colon-separated pair soft:hard to set both limits
individually (e.g. "LimitAS=4G:16G"). Use the string
infinity to configure no limit on a specific resource. The
multiplicative suffixes K, M, G, T, P and E (to the base
1024) may be used for resource limits measured in bytes (e.g.
"LimitAS=16G"). For the limits referring to time values, the
usual time units ms, s, min, h and so on may be used (see
systemd.time(7) for details). Note that if no time unit is
specified for LimitCPU= the default unit of seconds is
implied, while for LimitRTTIME= the default unit of
microseconds is implied. Also, note that the effective
granularity of the limits might influence their enforcement.
For example, time limits specified for LimitCPU= will be
rounded up implicitly to multiples of 1s. For LimitNICE= the
value may be specified in two syntaxes: if prefixed with "+"
or "-", the value is understood as regular Linux nice value
in the range -20...19. If not prefixed like this the value is
understood as raw resource limit parameter in the range
0...40 (with 0 being equivalent to 1).
Note that most process resource limits configured with these
options are per-process, and processes may fork in order to
acquire a new set of resources that are accounted
independently of the original process, and may thus escape
limits set. Also note that LimitRSS= is not implemented on
Linux, and setting it has no effect. Often it is advisable to
prefer the resource controls listed in
systemd.resource-control(5) over these per-process limits, as
they apply to services as a whole, may be altered dynamically
at runtime, and are generally more expressive. For example,
MemoryMax= is a more powerful (and working) replacement for
LimitRSS=.
Note that LimitNPROC= will limit the number of processes from
one (real) UID and not the number of processes started
(forked) by the service. Therefore the limit is cumulative
for all processes running under the same UID. Please also
note that the LimitNPROC= will not be enforced if the service
is running as root (and not dropping privileges). Due to
these limitations, TasksMax= (see
systemd.resource-control(5)) is typically a better choice
than LimitNPROC=.
Resource limits not configured explicitly for a unit default
to the value configured in the various DefaultLimitCPU=,
DefaultLimitFSIZE=, ... options available in
systemd-system.conf(5), and – if not configured there – the
kernel or per-user defaults, as defined by the OS (the latter
only for user services, see below).
For system units these resource limits may be chosen freely.
When these settings are configured in a user service (i.e. a
service run by the per-user instance of the service manager)
they cannot be used to raise the limits above those set for
the user manager itself when it was first invoked, as the
user's service manager generally lacks the privileges to do
so. In user context these configuration options are hence
only useful to lower the limits passed in or to raise the
soft limit to the maximum of the hard limit as configured for
the user. To raise the user's limits further, the available
configuration mechanisms differ between operating systems,
but typically require privileges. In most cases it is
possible to configure higher per-user resource limits via PAM
or by setting limits on the system service encapsulating the
user's service manager, i.e. the user's instance of
user@.service. After making such changes, make sure to
restart the user's service manager.
Table 1. Resource limit directives, their equivalent ulimit
shell commands and the unit used
┌──────────────────┬────────────┬────────────────┬──────────────────────────────┐
│ Directive │ ulimit │ Unit │ Notes │
│ │ equivalent │ │ │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitCPU= │ ulimit -t │ Seconds │ - │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitFSIZE= │ ulimit -f │ Bytes │ - │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitDATA= │ ulimit -d │ Bytes │ Don't use. │
│ │ │ │ This limits │
│ │ │ │ the allowed │
│ │ │ │ address range, │
│ │ │ │ not memory │
│ │ │ │ use! Defaults │
│ │ │ │ to unlimited │
│ │ │ │ and should not │
│ │ │ │ be lowered. To │
│ │ │ │ limit memory │
│ │ │ │ use, see │
│ │ │ │ MemoryMax= in │
│ │ │ │ systemd.resource-control(5). │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitSTACK= │ ulimit -s │ Bytes │ - │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitCORE= │ ulimit -c │ Bytes │ - │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitRSS= │ ulimit -m │ Bytes │ Don't use. No effect on │
│ │ │ │ Linux. │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitNOFILE= │ ulimit -n │ Number of File │ Don't use. Be careful when │
│ │ │ Descriptors │ raising the soft limit above │
│ │ │ │ 1024, since select(2) cannot │
│ │ │ │ function with file │
│ │ │ │ descriptors above 1023 on │
│ │ │ │ Linux. Nowadays, the hard │
│ │ │ │ limit defaults to 524288, a │
│ │ │ │ very high value compared to │
│ │ │ │ historical defaults. │
│ │ │ │ Typically applications │
│ │ │ │ should increase their soft │
│ │ │ │ limit to the hard limit on │
│ │ │ │ their own, if they are OK │
│ │ │ │ with working with file │
│ │ │ │ descriptors above 1023, i.e. │
│ │ │ │ do not use select(2). Note │
│ │ │ │ that file descriptors are │
│ │ │ │ nowadays accounted like any │
│ │ │ │ other form of memory, thus │
│ │ │ │ there should not be any need │
│ │ │ │ to lower the hard limit. Use │
│ │ │ │ MemoryMax= to control │
│ │ │ │ overall service memory use, │
│ │ │ │ including file descriptor │
│ │ │ │ memory. │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitAS= │ ulimit -v │ Bytes │ Don't use. This limits the │
│ │ │ │ allowed address range, not │
│ │ │ │ memory use! Defaults to │
│ │ │ │ unlimited and should not be │
│ │ │ │ lowered. To limit memory │
│ │ │ │ use, see MemoryMax= in │
│ │ │ │ systemd.resource-control(5). │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitNPROC= │ ulimit -u │ Number of │ This limit is enforced based │
│ │ │ Processes │ on the number of processes │
│ │ │ │ belonging to the user. │
│ │ │ │ Typically it's better to │
│ │ │ │ track processes per service, │
│ │ │ │ i.e. use TasksMax=, see │
│ │ │ │ systemd.resource-control(5). │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitMEMLOCK= │ ulimit -l │ Bytes │ - │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitLOCKS= │ ulimit -x │ Number of │ - │
│ │ │ Locks │ │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitSIGPENDING= │ ulimit -i │ Number of │ - │
│ │ │ Queued Signals │ │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitMSGQUEUE= │ ulimit -q │ Bytes │ - │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitNICE= │ ulimit -e │ Nice Level │ - │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitRTPRIO= │ ulimit -r │ Realtime │ - │
│ │ │ Priority │ │
├──────────────────┼────────────┼────────────────┼──────────────────────────────┤
│ LimitRTTIME= │ ulimit -R │ Microseconds │ - │
└──────────────────┴────────────┴────────────────┴──────────────────────────────┘
UMask=
Controls the file mode creation mask. Takes an access mode in
octal notation. See umask(2) for details. Defaults to 0022
for system units. For user units the default value is
inherited from the per-user service manager (whose default is
in turn inherited from the system service manager, and thus
typically also is 0022 — unless overridden by a PAM module).
In order to change the per-user mask for all user services,
consider setting the UMask= setting of the user's
user@.service system service instance. The per-user umask may
also be set via the umask field of a user's JSON User
Record[5] (for users managed by systemd-homed.service(8) this
field may be controlled via homectl --umask=). It may also be
set via a PAM module, such as pam_umask(8).
CoredumpFilter=
Controls which types of memory mappings will be saved if the
process dumps core (using the /proc/pid/coredump_filter
file). Takes a whitespace-separated combination of mapping
type names or numbers (with the default base 16). Mapping
type names are private-anonymous, shared-anonymous,
private-file-backed, shared-file-backed, elf-headers,
private-huge, shared-huge, private-dax, shared-dax, and the
special values all (all types) and default (the kernel
default of "private-anonymous shared-anonymous elf-headers
private-huge"). See core(5) for the meaning of the mapping
types. When specified multiple times, all specified masks are
ORed. When not set, or if the empty value is assigned, the
inherited value is not changed.
Example 2. Add DAX pages to the dump filter
CoredumpFilter=default private-dax shared-dax
Added in version 246.
KeyringMode=
Controls how the kernel session keyring is set up for the
service (see session-keyring(7) for details on the session
keyring). Takes one of inherit, private, shared. If set to
inherit no special keyring setup is done, and the kernel's
default behaviour is applied. If private is used a new
session keyring is allocated when a service process is
invoked, and it is not linked up with any user keyring. This
is the recommended setting for system services, as this
ensures that multiple services running under the same system
user ID (in particular the root user) do not share their key
material among each other. If shared is used a new session
keyring is allocated as for private, but the user keyring of
the user configured with User= is linked into it, so that
keys assigned to the user may be requested by the unit's
processes. In this mode multiple units running processes
under the same user ID may share key material. Unless inherit
is selected the unique invocation ID for the unit (see below)
is added as a protected key by the name "invocation_id" to
the newly created session keyring. Defaults to private for
services of the system service manager and to inherit for
non-service units and for services of the user service
manager.
Added in version 235.
OOMScoreAdjust=
Sets the adjustment value for the Linux kernel's
Out-Of-Memory (OOM) killer score for executed processes.
Takes an integer between -1000 (to disable OOM killing of
processes of this unit) and 1000 (to make killing of
processes of this unit under memory pressure very likely).
See The /proc Filesystem[6] for details. If not specified
defaults to the OOM score adjustment level of the service
manager itself, which is normally at 0.
Use the OOMPolicy= setting of service units to configure how
the service manager shall react to the kernel OOM killer or
systemd-oomd terminating a process of the service. See
systemd.service(5) for details.
TimerSlackNSec=
Sets the timer slack in nanoseconds for the executed
processes. The timer slack controls the accuracy of wake-ups
triggered by timers. See prctl(2) for more information. Note
that in contrast to most other time span definitions this
parameter takes an integer value in nano-seconds if no unit
is specified. The usual time units are understood too.
Personality=
Controls which kernel architecture uname(2) shall report,
when invoked by unit processes. Takes one of the architecture
identifiers arm64, arm64-be, arm, arm-be, x86, x86-64, ppc,
ppc-le, ppc64, ppc64-le, s390 or s390x. Which personality
architectures are supported depends on the kernel's native
architecture. Usually the 64-bit versions of the various
system architectures support their immediate 32-bit
personality architecture counterpart, but no others. For
example, x86-64 systems support the x86-64 and x86
personalities but no others. The personality feature is
useful when running 32-bit services on a 64-bit host system.
If not specified, the personality is left unmodified and thus
reflects the personality of the host system's kernel. This
option is not useful on architectures for which only one
native word width was ever available, such as m68k (32-bit
only) or alpha (64-bit only).
Added in version 209.
IgnoreSIGPIPE=
Takes a boolean argument. If true, SIGPIPE is ignored in the
executed process. Defaults to true since SIGPIPE is generally
only useful in shell pipelines.
Nice=
Sets the default nice level (scheduling priority) for
executed processes. Takes an integer between -20 (highest
priority) and 19 (lowest priority). In case of resource
contention, smaller values mean more resources will be made
available to the unit's processes, larger values mean less
resources will be made available. See setpriority(2) for
details.
CPUSchedulingPolicy=
Sets the CPU scheduling policy for executed processes. Takes
one of other, batch, idle, fifo or rr. See
sched_setscheduler(2) for details.
CPUSchedulingPriority=
Sets the CPU scheduling priority for executed processes. The
available priority range depends on the selected CPU
scheduling policy (see above). For real-time scheduling
policies an integer between 1 (lowest priority) and 99
(highest priority) can be used. In case of CPU resource
contention, smaller values mean less CPU time is made
available to the service, larger values mean more. See
sched_setscheduler(2) for details.
CPUSchedulingResetOnFork=
Takes a boolean argument. If true, elevated CPU scheduling
priorities and policies will be reset when the executed
processes call fork(2), and can hence not leak into child
processes. See sched_setscheduler(2) for details. Defaults to
false.
CPUAffinity=
Controls the CPU affinity of the executed processes. Takes a
list of CPU indices or ranges separated by either whitespace
or commas. Alternatively, takes a special "numa" value in
which case systemd automatically derives allowed CPU range
based on the value of NUMAMask= option. CPU ranges are
specified by the lower and upper CPU indices separated by a
dash. This option may be specified more than once, in which
case the specified CPU affinity masks are merged. If the
empty string is assigned, the mask is reset, all assignments
prior to this will have no effect. See sched_setaffinity(2)
for details.
NUMAPolicy=
Controls the NUMA memory policy of the executed processes.
Takes a policy type, one of: default, preferred, bind,
interleave and local. A list of NUMA nodes that should be
associated with the policy must be specified in NUMAMask=.
For more details on each policy please see, set_mempolicy(2).
For overall overview of NUMA support in Linux see, numa(7).
Added in version 243.
NUMAMask=
Controls the NUMA node list which will be applied alongside
with selected NUMA policy. Takes a list of NUMA nodes and has
the same syntax as a list of CPUs for CPUAffinity= option or
special "all" value which will include all available NUMA
nodes in the mask. Note that the list of NUMA nodes is not
required for default and local policies and for preferred
policy we expect a single NUMA node.
Added in version 243.
IOSchedulingClass=
Sets the I/O scheduling class for executed processes. Takes
one of the strings realtime, best-effort or idle. The
kernel's default scheduling class is best-effort at a
priority of 4. If the empty string is assigned to this
option, all prior assignments to both IOSchedulingClass= and
IOSchedulingPriority= have no effect. See ioprio_set(2) for
details.
IOSchedulingPriority=
Sets the I/O scheduling priority for executed processes.
Takes an integer between 0 (highest priority) and 7 (lowest
priority). In case of I/O contention, smaller values mean
more I/O bandwidth is made available to the unit's processes,
larger values mean less bandwidth. The available priorities
depend on the selected I/O scheduling class (see above). If
the empty string is assigned to this option, all prior
assignments to both IOSchedulingClass= and
IOSchedulingPriority= have no effect. For the kernel's
default scheduling class (best-effort) this defaults to 4.
See ioprio_set(2) for details.
The following sandboxing options are an effective way to limit
the exposure of the system towards the unit's processes. It is
recommended to turn on as many of these options for each unit as
is possible without negatively affecting the process' ability to
operate. Note that many of these sandboxing features are
gracefully turned off on systems where the underlying security
mechanism is not available. For example, ProtectSystem= has no
effect if the kernel is built without file system namespacing or
if the service manager runs in a container manager that makes
file system namespacing unavailable to its payload. Similarly,
RestrictRealtime= has no effect on systems that lack support for
SECCOMP system call filtering, or in containers where support for
this is turned off.
Also note that some sandboxing functionality is generally not
available in user services (i.e. services run by the per-user
service manager). Specifically, the various settings requiring
file system namespacing support (such as ProtectSystem=) are not
available, as the underlying kernel functionality is only
accessible to privileged processes. However, most namespacing
settings, that will not work on their own in user services, will
work when used in conjunction with PrivateUsers=true.
Note that the various options that turn directories read-only
(such as ProtectSystem=, ReadOnlyPaths=, ...) do not affect the
ability for programs to connect to and communicate with AF_UNIX
sockets in these directories. These options cannot be used to
lock down access to IPC services hence.
ProtectSystem=
Takes a boolean argument or the special values "full" or
"strict". If true, mounts the /usr/ and the boot loader
directories (/boot and /efi) read-only for processes invoked
by this unit. If set to "full", the /etc/ directory is
mounted read-only, too. If set to "strict" the entire file
system hierarchy is mounted read-only, except for the API
file system subtrees /dev/, /proc/ and /sys/ (protect these
directories using PrivateDevices=, ProtectKernelTunables=,
ProtectControlGroups=). This setting ensures that any
modification of the vendor-supplied operating system (and
optionally its configuration, and local mounts) is prohibited
for the service. It is recommended to enable this setting for
all long-running services, unless they are involved with
system updates or need to modify the operating system in
other ways. If this option is used, ReadWritePaths= may be
used to exclude specific directories from being made
read-only. Similar, StateDirectory=, LogsDirectory=, ... and
related directory settings (see below) also exclude the
specific directories from the effect of ProtectSystem=. This
setting is implied if DynamicUser= is set. This setting
cannot ensure protection in all cases. In general it has the
same limitations as ReadOnlyPaths=, see below. Defaults to
off.
Added in version 214.
ProtectHome=
Takes a boolean argument or the special values "read-only" or
"tmpfs". If true, the directories /home/, /root, and
/run/user are made inaccessible and empty for processes
invoked by this unit. If set to "read-only", the three
directories are made read-only instead. If set to "tmpfs",
temporary file systems are mounted on the three directories
in read-only mode. The value "tmpfs" is useful to hide home
directories not relevant to the processes invoked by the
unit, while still allowing necessary directories to be made
visible when listed in BindPaths= or BindReadOnlyPaths=.
Setting this to "yes" is mostly equivalent to setting the
three directories in InaccessiblePaths=. Similarly,
"read-only" is mostly equivalent to ReadOnlyPaths=, and
"tmpfs" is mostly equivalent to TemporaryFileSystem= with
":ro".
It is recommended to enable this setting for all long-running
services (in particular network-facing ones), to ensure they
cannot get access to private user data, unless the services
actually require access to the user's private data. This
setting is implied if DynamicUser= is set. This setting
cannot ensure protection in all cases. In general it has the
same limitations as ReadOnlyPaths=, see below.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
Added in version 214.
RuntimeDirectory=, StateDirectory=, CacheDirectory=,
LogsDirectory=, ConfigurationDirectory=
These options take a whitespace-separated list of directory
names. The specified directory names must be relative, and
may not include "..". If set, when the unit is started, one
or more directories by the specified names will be created
(including their parents) below the locations defined in the
following table. Also, the corresponding environment variable
will be defined with the full paths of the directories. If
multiple directories are set, then in the environment
variable the paths are concatenated with colon (":").
Table 2. Automatic directory creation and environment
variables
┌─────────────────────────┬────────────────┬──────────────────────┬──────────────────────────┐
│ Directory │ Below path for │ Below path for │ Environment │
│ │ system units │ user units │ variable set │
├─────────────────────────┼────────────────┼──────────────────────┼──────────────────────────┤
│ RuntimeDirectory= │ /run/ │ $XDG_RUNTIME_DIR │ $RUNTIME_DIRECTORY │
├─────────────────────────┼────────────────┼──────────────────────┼──────────────────────────┤
│ StateDirectory= │ /var/lib/ │ $XDG_STATE_HOME │ $STATE_DIRECTORY │
├─────────────────────────┼────────────────┼──────────────────────┼──────────────────────────┤
│ CacheDirectory= │ /var/cache/ │ $XDG_CACHE_HOME │ $CACHE_DIRECTORY │
├─────────────────────────┼────────────────┼──────────────────────┼──────────────────────────┤
│ LogsDirectory= │ /var/log/ │ $XDG_STATE_HOME/log/ │ $LOGS_DIRECTORY │
├─────────────────────────┼────────────────┼──────────────────────┼──────────────────────────┤
│ ConfigurationDirectory= │ /etc/ │ $XDG_CONFIG_HOME │ $CONFIGURATION_DIRECTORY │
└─────────────────────────┴────────────────┴──────────────────────┴──────────────────────────┘
In case of RuntimeDirectory= the innermost subdirectories are
removed when the unit is stopped. It is possible to preserve
the specified directories in this case if
RuntimeDirectoryPreserve= is configured to restart or yes
(see below). The directories specified with StateDirectory=,
CacheDirectory=, LogsDirectory=, ConfigurationDirectory= are
not removed when the unit is stopped.
Except in case of ConfigurationDirectory=, the innermost
specified directories will be owned by the user and group
specified in User= and Group=. If the specified directories
already exist and their owning user or group do not match the
configured ones, all files and directories below the
specified directories as well as the directories themselves
will have their file ownership recursively changed to match
what is configured. As an optimization, if the specified
directories are already owned by the right user and group,
files and directories below of them are left as-is, even if
they do not match what is requested. The innermost specified
directories will have their access mode adjusted to the what
is specified in RuntimeDirectoryMode=, StateDirectoryMode=,
CacheDirectoryMode=, LogsDirectoryMode= and
ConfigurationDirectoryMode=.
These options imply BindPaths= for the specified paths. When
combined with RootDirectory= or RootImage= these paths always
reside on the host and are mounted from there into the unit's
file system namespace.
If DynamicUser= is used, the logic for CacheDirectory=,
LogsDirectory= and StateDirectory= is slightly altered: the
directories are created below /var/cache/private,
/var/log/private and /var/lib/private, respectively, which
are host directories made inaccessible to unprivileged users,
which ensures that access to these directories cannot be
gained through dynamic user ID recycling. Symbolic links are
created to hide this difference in behaviour. Both from
perspective of the host and from inside the unit, the
relevant directories hence always appear directly below
/var/cache, /var/log and /var/lib.
Use RuntimeDirectory= to manage one or more runtime
directories for the unit and bind their lifetime to the
daemon runtime. This is particularly useful for unprivileged
daemons that cannot create runtime directories in /run/ due
to lack of privileges, and to make sure the runtime directory
is cleaned up automatically after use. For runtime
directories that require more complex or different
configuration or lifetime guarantees, please consider using
tmpfiles.d(5).
RuntimeDirectory=, StateDirectory=, CacheDirectory= and
LogsDirectory= optionally support a second parameter,
separated by ":". The second parameter will be interpreted as
a destination path that will be created as a symlink to the
directory. The symlinks will be created after any BindPaths=
or TemporaryFileSystem= options have been set up, to make
ephemeral symlinking possible. The same source can have
multiple symlinks, by using the same first parameter, but a
different second parameter.
The directories defined by these options are always created
under the standard paths used by systemd (/var/, /run/,
/etc/, ...). If the service needs directories in a different
location, a different mechanism has to be used to create
them.
tmpfiles.d(5) provides functionality that overlaps with these
options. Using these options is recommended, because the
lifetime of the directories is tied directly to the lifetime
of the unit, and it is not necessary to ensure that the
tmpfiles.d configuration is executed before the unit is
started.
To remove any of the directories created by these settings,
use the systemctl clean ... command on the relevant units,
see systemctl(1) for details.
Example: if a system service unit has the following,
RuntimeDirectory=foo/bar baz
the service manager creates /run/foo (if it does not exist),
/run/foo/bar, and /run/baz. The directories /run/foo/bar and
/run/baz except /run/foo are owned by the user and group
specified in User= and Group=, and removed when the service
is stopped.
Example: if a system service unit has the following,
RuntimeDirectory=foo/bar
StateDirectory=aaa/bbb ccc
then the environment variable "RUNTIME_DIRECTORY" is set with
"/run/foo/bar", and "STATE_DIRECTORY" is set with
"/var/lib/aaa/bbb:/var/lib/ccc".
Example: if a system service unit has the following,
RuntimeDirectory=foo:bar foo:baz
the service manager creates /run/foo (if it does not exist),
and /run/bar plus /run/baz as symlinks to /run/foo.
Added in version 211.
RuntimeDirectoryMode=, StateDirectoryMode=, CacheDirectoryMode=,
LogsDirectoryMode=, ConfigurationDirectoryMode=
Specifies the access mode of the directories specified in
RuntimeDirectory=, StateDirectory=, CacheDirectory=,
LogsDirectory=, or ConfigurationDirectory=, respectively, as
an octal number. Defaults to 0755. See "Permissions" in
path_resolution(7) for a discussion of the meaning of
permission bits.
Added in version 234.
RuntimeDirectoryPreserve=
Takes a boolean argument or restart. If set to no (the
default), the directories specified in RuntimeDirectory= are
always removed when the service stops. If set to restart the
directories are preserved when the service is both
automatically and manually restarted. Here, the automatic
restart means the operation specified in Restart=, and manual
restart means the one triggered by systemctl restart
foo.service. If set to yes, then the directories are not
removed when the service is stopped. Note that since the
runtime directory /run/ is a mount point of "tmpfs", then for
system services the directories specified in
RuntimeDirectory= are removed when the system is rebooted.
Added in version 235.
TimeoutCleanSec=
Configures a timeout on the clean-up operation requested
through systemctl clean ..., see systemctl(1) for details.
Takes the usual time values and defaults to infinity, i.e. by
default no timeout is applied. If a timeout is configured the
clean operation will be aborted forcibly when the timeout is
reached, potentially leaving resources on disk.
Added in version 244.
ReadWritePaths=, ReadOnlyPaths=, InaccessiblePaths=, ExecPaths=,
NoExecPaths=
Sets up a new file system namespace for executed processes.
These options may be used to limit access a process has to
the file system. Each setting takes a space-separated list of
paths relative to the host's root directory (i.e. the system
running the service manager). Note that if paths contain
symlinks, they are resolved relative to the root directory
set with RootDirectory=/RootImage=.
Paths listed in ReadWritePaths= are accessible from within
the namespace with the same access modes as from outside of
it. Paths listed in ReadOnlyPaths= are accessible for reading
only, writing will be refused even if the usual file access
controls would permit this. Nest ReadWritePaths= inside of
ReadOnlyPaths= in order to provide writable subdirectories
within read-only directories. Use ReadWritePaths= in order to
allow-list specific paths for write access if
ProtectSystem=strict is used. Note that ReadWritePaths=
cannot be used to gain write access to a file system whose
superblock is mounted read-only. On Linux, for each mount
point write access is granted only if the mount point itself
and the file system superblock backing it are not marked
read-only. ReadWritePaths= only controls the former, not the
latter, hence a read-only file system superblock remains
protected.
Paths listed in InaccessiblePaths= will be made inaccessible
for processes inside the namespace along with everything
below them in the file system hierarchy. This may be more
restrictive than desired, because it is not possible to nest
ReadWritePaths=, ReadOnlyPaths=, BindPaths=, or
BindReadOnlyPaths= inside it. For a more flexible option, see
TemporaryFileSystem=.
Content in paths listed in NoExecPaths= are not executable
even if the usual file access controls would permit this.
Nest ExecPaths= inside of NoExecPaths= in order to provide
executable content within non-executable directories.
Non-directory paths may be specified as well. These options
may be specified more than once, in which case all paths
listed will have limited access from within the namespace. If
the empty string is assigned to this option, the specific
list is reset, and all prior assignments have no effect.
Paths in ReadWritePaths=, ReadOnlyPaths=, InaccessiblePaths=,
ExecPaths= and NoExecPaths= may be prefixed with "-", in
which case they will be ignored when they do not exist. If
prefixed with "+" the paths are taken relative to the root
directory of the unit, as configured with
RootDirectory=/RootImage=, instead of relative to the root
directory of the host (see above). When combining "-" and "+"
on the same path make sure to specify "-" first, and "+"
second.
Note that these settings will disconnect propagation of
mounts from the unit's processes to the host. This means that
this setting may not be used for services which shall be able
to install mount points in the main mount namespace. For
ReadWritePaths= and ReadOnlyPaths=, propagation in the other
direction is not affected, i.e. mounts created on the host
generally appear in the unit processes' namespace, and mounts
removed on the host also disappear there too. In particular,
note that mount propagation from host to unit will result in
unmodified mounts to be created in the unit's namespace, i.e.
writable mounts appearing on the host will be writable in the
unit's namespace too, even when propagated below a path
marked with ReadOnlyPaths=! Restricting access with these
options hence does not extend to submounts of a directory
that are created later on. This means the lock-down offered
by that setting is not complete, and does not offer full
protection.
Note that the effect of these settings may be undone by
privileged processes. In order to set up an effective
sandboxed environment for a unit it is thus recommended to
combine these settings with either
CapabilityBoundingSet=~CAP_SYS_ADMIN or
SystemCallFilter=~@mount.
Please be extra careful when applying these options to API
file systems (a list of them could be found in MountAPIVPS=),
since they may be required for basic system functionalities.
Moreover, /run/ needs to be writable for setting up mount
namespace and propagation.
Simple allow-list example using these directives:
[Service]
ReadOnlyPaths=/
ReadWritePaths=/var /run
InaccessiblePaths=-/lost+found
NoExecPaths=/
ExecPaths=/usr/sbin/my_daemon /usr/lib /usr/lib64
These options are only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
Added in version 231.
TemporaryFileSystem=
Takes a space-separated list of mount points for temporary
file systems (tmpfs). If set, a new file system namespace is
set up for executed processes, and a temporary file system is
mounted on each mount point. This option may be specified
more than once, in which case temporary file systems are
mounted on all listed mount points. If the empty string is
assigned to this option, the list is reset, and all prior
assignments have no effect. Each mount point may optionally
be suffixed with a colon (":") and mount options such as
"size=10%" or "ro". By default, each temporary file system is
mounted with "nodev,strictatime,mode=0755". These can be
disabled by explicitly specifying the corresponding mount
options, e.g., "dev" or "nostrictatime".
This is useful to hide files or directories not relevant to
the processes invoked by the unit, while necessary files or
directories can be still accessed by combining with
BindPaths= or BindReadOnlyPaths=:
Example: if a unit has the following,
TemporaryFileSystem=/var:ro
BindReadOnlyPaths=/var/lib/systemd
then the invoked processes by the unit cannot see any files
or directories under /var/ except for /var/lib/systemd or its
contents.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
Added in version 238.
PrivateTmp=
Takes a boolean argument. If true, sets up a new file system
namespace for the executed processes and mounts private /tmp/
and /var/tmp/ directories inside it that are not shared by
processes outside of the namespace. This is useful to secure
access to temporary files of the process, but makes sharing
between processes via /tmp/ or /var/tmp/ impossible. If true,
all temporary files created by a service in these directories
will be removed after the service is stopped. Defaults to
false. It is possible to run two or more units within the
same private /tmp/ and /var/tmp/ namespace by using the
JoinsNamespaceOf= directive, see systemd.unit(5) for details.
This setting is implied if DynamicUser= is set. For this
setting, the same restrictions regarding mount propagation
and privileges apply as for ReadOnlyPaths= and related calls,
see above. Enabling this setting has the side effect of
adding Requires= and After= dependencies on all mount units
necessary to access /tmp/ and /var/tmp/. Moreover an
implicitly After= ordering on
systemd-tmpfiles-setup.service(8) is added.
Note that the implementation of this setting might be
impossible (for example if mount namespaces are not
available), and the unit should be written in a way that does
not solely rely on this setting for security.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
PrivateDevices=
Takes a boolean argument. If true, sets up a new /dev/ mount
for the executed processes and only adds API pseudo devices
such as /dev/null, /dev/zero or /dev/random (as well as the
pseudo TTY subsystem) to it, but no physical devices such as
/dev/sda, system memory /dev/mem, system ports /dev/port and
others. This is useful to turn off physical device access by
the executed process. Defaults to false.
Enabling this option will install a system call filter to
block low-level I/O system calls that are grouped in the
@raw-io set, remove CAP_MKNOD and CAP_SYS_RAWIO from the
capability bounding set for the unit, and set
DevicePolicy=closed (see systemd.resource-control(5) for
details). Note that using this setting will disconnect
propagation of mounts from the service to the host
(propagation in the opposite direction continues to work).
This means that this setting may not be used for services
which shall be able to install mount points in the main mount
namespace. The new /dev/ will be mounted read-only and
'noexec'. The latter may break old programs which try to set
up executable memory by using mmap(2) of /dev/zero instead of
using MAP_ANON. For this setting the same restrictions
regarding mount propagation and privileges apply as for
ReadOnlyPaths= and related calls, see above.
Note that the implementation of this setting might be
impossible (for example if mount namespaces are not
available), and the unit should be written in a way that does
not solely rely on this setting for security.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
When access to some but not all devices must be possible, the
DeviceAllow= setting might be used instead. See
systemd.resource-control(5).
Added in version 209.
PrivateNetwork=
Takes a boolean argument. If true, sets up a new network
namespace for the executed processes and configures only the
loopback network device "lo" inside it. No other network
devices will be available to the executed process. This is
useful to turn off network access by the executed process.
Defaults to false. It is possible to run two or more units
within the same private network namespace by using the
JoinsNamespaceOf= directive, see systemd.unit(5) for details.
Note that this option will disconnect all socket families
from the host, including AF_NETLINK and AF_UNIX. Effectively,
for AF_NETLINK this means that device configuration events
received from systemd-udevd.service(8) are not delivered to
the unit's processes. And for AF_UNIX this has the effect
that AF_UNIX sockets in the abstract socket namespace of the
host will become unavailable to the unit's processes
(however, those located in the file system will continue to
be accessible).
Note that the implementation of this setting might be
impossible (for example if network namespaces are not
available), and the unit should be written in a way that does
not solely rely on this setting for security.
When this option is enabled, PrivateMounts= is implied unless
it is explicitly disabled, and /sys will be remounted to
associate it with the new network namespace.
When this option is used on a socket unit any sockets bound
on behalf of this unit will be bound within a private network
namespace. This may be combined with JoinsNamespaceOf= to
listen on sockets inside of network namespaces of other
services.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
NetworkNamespacePath=
Takes an absolute file system path referring to a Linux
network namespace pseudo-file (i.e. a file like
/proc/$PID/ns/net or a bind mount or symlink to one). When
set the invoked processes are added to the network namespace
referenced by that path. The path has to point to a valid
namespace file at the moment the processes are forked off. If
this option is used PrivateNetwork= has no effect. If this
option is used together with JoinsNamespaceOf= then it only
has an effect if this unit is started before any of the
listed units that have PrivateNetwork= or
NetworkNamespacePath= configured, as otherwise the network
namespace of those units is reused.
When this option is enabled, PrivateMounts= is implied unless
it is explicitly disabled, and /sys will be remounted to
associate it with the new network namespace.
When this option is used on a socket unit any sockets bound
on behalf of this unit will be bound within the specified
network namespace.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
Added in version 242.
PrivateIPC=
Takes a boolean argument. If true, sets up a new IPC
namespace for the executed processes. Each IPC namespace has
its own set of System V IPC identifiers and its own POSIX
message queue file system. This is useful to avoid name clash
of IPC identifiers. Defaults to false. It is possible to run
two or more units within the same private IPC namespace by
using the JoinsNamespaceOf= directive, see systemd.unit(5)
for details.
Note that IPC namespacing does not have an effect on AF_UNIX
sockets, which are the most common form of IPC used on Linux.
Instead, AF_UNIX sockets in the file system are subject to
mount namespacing, and those in the abstract namespace are
subject to network namespacing. IPC namespacing only has an
effect on SysV IPC (which is mostly legacy) as well as POSIX
message queues (for which AF_UNIX/SOCK_SEQPACKET sockets are
typically a better replacement). IPC namespacing also has no
effect on POSIX shared memory (which is subject to mount
namespacing) either. See ipc_namespaces(7) for the details.
Note that the implementation of this setting might be
impossible (for example if IPC namespaces are not available),
and the unit should be written in a way that does not solely
rely on this setting for security.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
Added in version 248.
IPCNamespacePath=
Takes an absolute file system path referring to a Linux IPC
namespace pseudo-file (i.e. a file like /proc/$PID/ns/ipc or
a bind mount or symlink to one). When set the invoked
processes are added to the network namespace referenced by
that path. The path has to point to a valid namespace file at
the moment the processes are forked off. If this option is
used PrivateIPC= has no effect. If this option is used
together with JoinsNamespaceOf= then it only has an effect if
this unit is started before any of the listed units that have
PrivateIPC= or IPCNamespacePath= configured, as otherwise the
network namespace of those units is reused.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
Added in version 248.
MemoryKSM=
Takes a boolean argument. When set, it enables KSM (kernel
samepage merging) for the processes. KSM is a memory-saving
de-duplication feature. Anonymous memory pages with identical
content can be replaced by a single write-protected page.
This feature should only be enabled for jobs that share the
same security domain. For details, see Kernel Samepage
Merging[7] in the kernel documentation.
Note that this functionality might not be available, for
example if KSM is disabled in the kernel, or the kernel
doesn't support controlling KSM at the process level through
prctl(2).
Added in version 254.
PrivateUsers=
Takes a boolean argument. If true, sets up a new user
namespace for the executed processes and configures a minimal
user and group mapping, that maps the "root" user and group
as well as the unit's own user and group to themselves and
everything else to the "nobody" user and group. This is
useful to securely detach the user and group databases used
by the unit from the rest of the system, and thus to create
an effective sandbox environment. All files, directories,
processes, IPC objects and other resources owned by
users/groups not equaling "root" or the unit's own will stay
visible from within the unit but appear owned by the "nobody"
user and group. If this mode is enabled, all unit processes
are run without privileges in the host user namespace
(regardless if the unit's own user/group is "root" or not).
Specifically this means that the process will have zero
process capabilities on the host's user namespace, but full
capabilities within the service's user namespace. Settings
such as CapabilityBoundingSet= will affect only the latter,
and there's no way to acquire additional capabilities in the
host's user namespace. Defaults to off.
When this setting is set up by a per-user instance of the
service manager, the mapping of the "root" user and group to
itself is omitted (unless the user manager is root).
Additionally, in the per-user instance manager case, the user
namespace will be set up before most other namespaces. This
means that combining PrivateUsers=true with other namespaces
will enable use of features not normally supported by the
per-user instances of the service manager.
This setting is particularly useful in conjunction with
RootDirectory=/RootImage=, as the need to synchronize the
user and group databases in the root directory and on the
host is reduced, as the only users and groups who need to be
matched are "root", "nobody" and the unit's own user and
group.
Note that the implementation of this setting might be
impossible (for example if user namespaces are not
available), and the unit should be written in a way that does
not solely rely on this setting for security.
Added in version 232.
ProtectHostname=
Takes a boolean argument. When set, sets up a new UTS
namespace for the executed processes. In addition, changing
hostname or domainname is prevented. Defaults to off.
Note that the implementation of this setting might be
impossible (for example if UTS namespaces are not available),
and the unit should be written in a way that does not solely
rely on this setting for security.
Note that when this option is enabled for a service hostname
changes no longer propagate from the system into the service,
it is hence not suitable for services that need to take
notice of system hostname changes dynamically.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
Added in version 242.
ProtectClock=
Takes a boolean argument. If set, writes to the hardware
clock or system clock will be denied. Defaults to off.
Enabling this option removes CAP_SYS_TIME and CAP_WAKE_ALARM
from the capability bounding set for this unit, installs a
system call filter to block calls that can set the clock, and
DeviceAllow=char-rtc r is implied. Note that the system calls
are blocked altogether, the filter does not take into account
that some of the calls can be used to read the clock state
with some parameter combinations. Effectively, /dev/rtc0,
/dev/rtc1, etc. are made read-only to the service. See
systemd.resource-control(5) for the details about
DeviceAllow=.
It is recommended to turn this on for most services that do
not need modify the clock or check its state.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
Added in version 245.
ProtectKernelTunables=
Takes a boolean argument. If true, kernel variables
accessible through /proc/sys/, /sys/, /proc/sysrq-trigger,
/proc/latency_stats, /proc/acpi, /proc/timer_stats, /proc/fs
and /proc/irq will be made read-only to all processes of the
unit. Usually, tunable kernel variables should be initialized
only at boot-time, for example with the sysctl.d(5)
mechanism. Few services need to write to these at runtime; it
is hence recommended to turn this on for most services. For
this setting the same restrictions regarding mount
propagation and privileges apply as for ReadOnlyPaths= and
related calls, see above. Defaults to off. Note that this
option does not prevent indirect changes to kernel tunables
effected by IPC calls to other processes. However,
InaccessiblePaths= may be used to make relevant IPC file
system objects inaccessible. If ProtectKernelTunables= is
set, MountAPIVFS=yes is implied.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
Added in version 232.
ProtectKernelModules=
Takes a boolean argument. If true, explicit module loading
will be denied. This allows module load and unload operations
to be turned off on modular kernels. It is recommended to
turn this on for most services that do not need special file
systems or extra kernel modules to work. Defaults to off.
Enabling this option removes CAP_SYS_MODULE from the
capability bounding set for the unit, and installs a system
call filter to block module system calls, also
/usr/lib/modules is made inaccessible. For this setting the
same restrictions regarding mount propagation and privileges
apply as for ReadOnlyPaths= and related calls, see above.
Note that limited automatic module loading due to user
configuration or kernel mapping tables might still happen as
side effect of requested user operations, both privileged and
unprivileged. To disable module auto-load feature please see
sysctl.d(5) kernel.modules_disabled mechanism and
/proc/sys/kernel/modules_disabled documentation.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
Added in version 232.
ProtectKernelLogs=
Takes a boolean argument. If true, access to the kernel log
ring buffer will be denied. It is recommended to turn this on
for most services that do not need to read from or write to
the kernel log ring buffer. Enabling this option removes
CAP_SYSLOG from the capability bounding set for this unit,
and installs a system call filter to block the syslog(2)
system call (not to be confused with the libc API syslog(3)
for userspace logging). The kernel exposes its log buffer to
userspace via /dev/kmsg and /proc/kmsg. If enabled, these are
made inaccessible to all the processes in the unit.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
Added in version 244.
ProtectControlGroups=
Takes a boolean argument. If true, the Linux Control Groups
(cgroups(7)) hierarchies accessible through /sys/fs/cgroup/
will be made read-only to all processes of the unit. Except
for container managers no services should require write
access to the control groups hierarchies; it is hence
recommended to turn this on for most services. For this
setting the same restrictions regarding mount propagation and
privileges apply as for ReadOnlyPaths= and related calls, see
above. Defaults to off. If ProtectControlGroups= is set,
MountAPIVFS=yes is implied.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
Added in version 232.
RestrictAddressFamilies=
Restricts the set of socket address families accessible to
the processes of this unit. Takes "none", or a
space-separated list of address family names to allow-list,
such as AF_UNIX, AF_INET or AF_INET6. When "none" is
specified, then all address families will be denied. When
prefixed with "~" the listed address families will be applied
as deny list, otherwise as allow list. Note that this
restricts access to the socket(2) system call only. Sockets
passed into the process by other means (for example, by using
socket activation with socket units, see systemd.socket(5))
are unaffected. Also, sockets created with socketpair()
(which creates connected AF_UNIX sockets only) are
unaffected. Note that this option has no effect on 32-bit
x86, s390, s390x, mips, mips-le, ppc, ppc-le, ppc64, ppc64-le
and is ignored (but works correctly on other ABIs, including
x86-64). Note that on systems supporting multiple ABIs (such
as x86/x86-64) it is recommended to turn off alternative ABIs
for services, so that they cannot be used to circumvent the
restrictions of this option. Specifically, it is recommended
to combine this option with SystemCallArchitectures=native or
similar. By default, no restrictions apply, all address
families are accessible to processes. If assigned the empty
string, any previous address family restriction changes are
undone. This setting does not affect commands prefixed with
"+".
Use this option to limit exposure of processes to remote
access, in particular via exotic and sensitive network
protocols, such as AF_PACKET. Note that in most cases, the
local AF_UNIX address family should be included in the
configured allow list as it is frequently used for local
communication, including for syslog(2) logging.
Added in version 211.
RestrictFileSystems=
Restricts the set of filesystems processes of this unit can
open files on. Takes a space-separated list of filesystem
names. Any filesystem listed is made accessible to the unit's
processes, access to filesystem types not listed is
prohibited (allow-listing). If the first character of the
list is "~", the effect is inverted: access to the
filesystems listed is prohibited (deny-listing). If the empty
string is assigned, access to filesystems is not restricted.
If you specify both types of this option (i.e. allow-listing
and deny-listing), the first encountered will take precedence
and will dictate the default action (allow access to the
filesystem or deny it). Then the next occurrences of this
option will add or delete the listed filesystems from the set
of the restricted filesystems, depending on its type and the
default action.
Example: if a unit has the following,
RestrictFileSystems=ext4 tmpfs
RestrictFileSystems=ext2 ext4
then access to ext4, tmpfs, and ext2 is allowed and access to
other filesystems is denied.
Example: if a unit has the following,
RestrictFileSystems=ext4 tmpfs
RestrictFileSystems=~ext4
then only access tmpfs is allowed.
Example: if a unit has the following,
RestrictFileSystems=~ext4 tmpfs
RestrictFileSystems=ext4
then only access to tmpfs is denied.
As the number of possible filesystems is large, predefined
sets of filesystems are provided. A set starts with "@"
character, followed by name of the set.
Table 3. Currently predefined filesystem sets
┌───────────────────┬──────────────────────────┐
│ Set │ Description │
├───────────────────┼──────────────────────────┤
│ @basic-api │ Basic filesystem API. │
├───────────────────┼──────────────────────────┤
│ @auxiliary-api │ Auxiliary filesystem │
│ │ API. │
├───────────────────┼──────────────────────────┤
│ @common-block │ Common block device │
│ │ filesystems. │
├───────────────────┼──────────────────────────┤
│ @historical-block │ Historical block device │
│ │ filesystems. │
├───────────────────┼──────────────────────────┤
│ @network │ Well-known network │
│ │ filesystems. │
├───────────────────┼──────────────────────────┤
│ @privileged-api │ Privileged filesystem │
│ │ API. │
├───────────────────┼──────────────────────────┤
│ @temporary │ Temporary filesystems: │
│ │ tmpfs, ramfs. │
├───────────────────┼──────────────────────────┤
│ @known │ All known filesystems │
│ │ defined by the kernel. │
│ │ This list is defined │
│ │ statically in systemd │
│ │ based on a kernel │
│ │ version that was │
│ │ available when this │
│ │ systemd version was │
│ │ released. It will become │
│ │ progressively more │
│ │ out-of-date as the │
│ │ kernel is updated. │
└───────────────────┴──────────────────────────┘
Use systemd-analyze(1)'s filesystems command to retrieve a
list of filesystems defined on the local system.
Note that this setting might not be supported on some systems
(for example if the LSM eBPF hook is not enabled in the
underlying kernel or if not using the unified control group
hierarchy). In that case this setting has no effect.
This option cannot be bypassed by prefixing "+" to the
executable path in the service unit, as it applies to the
whole control group.
Added in version 250.
RestrictNamespaces=
Restricts access to Linux namespace functionality for the
processes of this unit. For details about Linux namespaces,
see namespaces(7). Either takes a boolean argument, or a
space-separated list of namespace type identifiers. If false
(the default), no restrictions on namespace creation and
switching are made. If true, access to any kind of
namespacing is prohibited. Otherwise, a space-separated list
of namespace type identifiers must be specified, consisting
of any combination of: cgroup, ipc, net, mnt, pid, user and
uts. Any namespace type listed is made accessible to the
unit's processes, access to namespace types not listed is
prohibited (allow-listing). By prepending the list with a
single tilde character ("~") the effect may be inverted: only
the listed namespace types will be made inaccessible, all
unlisted ones are permitted (deny-listing). If the empty
string is assigned, the default namespace restrictions are
applied, which is equivalent to false. This option may appear
more than once, in which case the namespace types are merged
by OR, or by AND if the lines are prefixed with "~" (see
examples below). Internally, this setting limits access to
the unshare(2), clone(2) and setns(2) system calls, taking
the specified flags parameters into account. Note that — if
this option is used — in addition to restricting creation and
switching of the specified types of namespaces (or all of
them, if true) access to the setns() system call with a zero
flags parameter is prohibited. This setting is only supported
on x86, x86-64, mips, mips-le, mips64, mips64-le, mips64-n32,
mips64-le-n32, ppc64, ppc64-le, s390 and s390x, and enforces
no restrictions on other architectures.
Example: if a unit has the following,
RestrictNamespaces=cgroup ipc
RestrictNamespaces=cgroup net
then cgroup, ipc, and net are set. If the second line is
prefixed with "~", e.g.,
RestrictNamespaces=cgroup ipc
RestrictNamespaces=~cgroup net
then, only ipc is set.
Added in version 233.
LockPersonality=
Takes a boolean argument. If set, locks down the
personality(2) system call so that the kernel execution
domain may not be changed from the default or the personality
selected with Personality= directive. This may be useful to
improve security, because odd personality emulations may be
poorly tested and source of vulnerabilities.
Added in version 235.
MemoryDenyWriteExecute=
Takes a boolean argument. If set, attempts to create memory
mappings that are writable and executable at the same time,
or to change existing memory mappings to become executable,
or mapping shared memory segments as executable, are
prohibited. Specifically, a system call filter is added (or
preferably, an equivalent kernel check is enabled with
prctl(2)) that rejects mmap(2) system calls with both
PROT_EXEC and PROT_WRITE set, mprotect(2) or pkey_mprotect(2)
system calls with PROT_EXEC set and shmat(2) system calls
with SHM_EXEC set. Note that this option is incompatible with
programs and libraries that generate program code dynamically
at runtime, including JIT execution engines, executable
stacks, and code "trampoline" feature of various C compilers.
This option improves service security, as it makes harder for
software exploits to change running code dynamically.
However, the protection can be circumvented, if the service
can write to a filesystem, which is not mounted with noexec
(such as /dev/shm), or it can use memfd_create(). This can be
prevented by making such file systems inaccessible to the
service (e.g. InaccessiblePaths=/dev/shm) and installing
further system call filters (SystemCallFilter=~memfd_create).
Note that this feature is fully available on x86-64, and
partially on x86. Specifically, the shmat() protection is not
available on x86. Note that on systems supporting multiple
ABIs (such as x86/x86-64) it is recommended to turn off
alternative ABIs for services, so that they cannot be used to
circumvent the restrictions of this option. Specifically, it
is recommended to combine this option with
SystemCallArchitectures=native or similar.
Added in version 231.
RestrictRealtime=
Takes a boolean argument. If set, any attempts to enable
realtime scheduling in a process of the unit are refused.
This restricts access to realtime task scheduling policies
such as SCHED_FIFO, SCHED_RR or SCHED_DEADLINE. See sched(7)
for details about these scheduling policies. Realtime
scheduling policies may be used to monopolize CPU time for
longer periods of time, and may hence be used to lock up or
otherwise trigger Denial-of-Service situations on the system.
It is hence recommended to restrict access to realtime
scheduling to the few programs that actually require them.
Defaults to off.
Added in version 231.
RestrictSUIDSGID=
Takes a boolean argument. If set, any attempts to set the
set-user-ID (SUID) or set-group-ID (SGID) bits on files or
directories will be denied (for details on these bits see
inode(7)). As the SUID/SGID bits are mechanisms to elevate
privileges, and allow users to acquire the identity of other
users, it is recommended to restrict creation of SUID/SGID
files to the few programs that actually require them. Note
that this restricts marking of any type of file system object
with these bits, including both regular files and directories
(where the SGID is a different meaning than for files, see
documentation). This option is implied if DynamicUser= is
enabled. Defaults to off.
Added in version 242.
RemoveIPC=
Takes a boolean parameter. If set, all System V and POSIX IPC
objects owned by the user and group the processes of this
unit are run as are removed when the unit is stopped. This
setting only has an effect if at least one of User=, Group=
and DynamicUser= are used. It has no effect on IPC objects
owned by the root user. Specifically, this removes System V
semaphores, as well as System V and POSIX shared memory
segments and message queues. If multiple units use the same
user or group the IPC objects are removed when the last of
these units is stopped. This setting is implied if
DynamicUser= is set.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
Added in version 232.
PrivateMounts=
Takes a boolean parameter. If set, the processes of this unit
will be run in their own private file system (mount)
namespace with all mount propagation from the processes
towards the host's main file system namespace turned off.
This means any file system mount points established or
removed by the unit's processes will be private to them and
not be visible to the host. However, file system mount points
established or removed on the host will be propagated to the
unit's processes. See mount_namespaces(7) for details on file
system namespaces. Defaults to off.
When turned on, this executes three operations for each
invoked process: a new CLONE_NEWNS namespace is created,
after which all existing mounts are remounted to MS_SLAVE to
disable propagation from the unit's processes to the host
(but leaving propagation in the opposite direction in
effect). Finally, the mounts are remounted again to the
propagation mode configured with MountFlags=, see below.
File system namespaces are set up individually for each
process forked off by the service manager. Mounts established
in the namespace of the process created by ExecStartPre= will
hence be cleaned up automatically as soon as that process
exits and will not be available to subsequent processes
forked off for ExecStart= (and similar applies to the various
other commands configured for units). Similarly,
JoinsNamespaceOf= does not permit sharing kernel mount
namespaces between units, it only enables sharing of the
/tmp/ and /var/tmp/ directories.
Other file system namespace unit settings — PrivateTmp=,
PrivateDevices=, ProtectSystem=, ProtectHome=,
ReadOnlyPaths=, InaccessiblePaths=, ReadWritePaths=,
BindPaths=, BindReadOnlyPaths=, ... — also enable file system
namespacing in a fashion equivalent to this option. Hence it
is primarily useful to explicitly request this behaviour if
none of the other settings are used.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
Added in version 239.
MountFlags=
Takes a mount propagation setting: shared, slave or private,
which controls whether file system mount points in the file
system namespaces set up for this unit's processes will
receive or propagate mounts and unmounts from other file
system namespaces. See mount(2) for details on mount
propagation, and the three propagation flags in particular.
This setting only controls the final propagation setting in
effect on all mount points of the file system namespace
created for each process of this unit. Other file system
namespacing unit settings (see the discussion in
PrivateMounts= above) will implicitly disable mount and
unmount propagation from the unit's processes towards the
host by changing the propagation setting of all mount points
in the unit's file system namespace to slave first. Setting
this option to shared does not reestablish propagation in
that case.
If not set – but file system namespaces are enabled through
another file system namespace unit setting – shared mount
propagation is used, but — as mentioned — as slave is applied
first, propagation from the unit's processes to the host is
still turned off.
It is not recommended to use private mount propagation for
units, as this means temporary mounts (such as removable
media) of the host will stay mounted and thus indefinitely
busy in forked off processes, as unmount propagation events
won't be received by the file system namespace of the unit.
Usually, it is best to leave this setting unmodified, and use
higher level file system namespacing options instead, in
particular PrivateMounts=, see above.
This option is only available for system services, or for
services running in per-user instances of the service manager
in which case PrivateUsers= is implicitly enabled (requires
unprivileged user namespaces support to be enabled in the
kernel via the "kernel.unprivileged_userns_clone=" sysctl).
SystemCallFilter=
Takes a space-separated list of system call names. If this
setting is used, all system calls executed by the unit
processes except for the listed ones will result in immediate
process termination with the SIGSYS signal (allow-listing).
(See SystemCallErrorNumber= below for changing the default
action). If the first character of the list is "~", the
effect is inverted: only the listed system calls will result
in immediate process termination (deny-listing). Deny-listed
system calls and system call groups may optionally be
suffixed with a colon (":") and "errno" error number (between
0 and 4095) or errno name such as EPERM, EACCES or EUCLEAN
(see errno(3) for a full list). This value will be returned
when a deny-listed system call is triggered, instead of
terminating the processes immediately. Special setting "kill"
can be used to explicitly specify killing. This value takes
precedence over the one given in SystemCallErrorNumber=, see
below. This feature makes use of the Secure Computing Mode 2
interfaces of the kernel ('seccomp filtering') and is useful
for enforcing a minimal sandboxing environment. Note that the
execve(), exit(), exit_group(), getrlimit(), rt_sigreturn(),
sigreturn() system calls and the system calls for querying
time and sleeping are implicitly allow-listed and do not need
to be listed explicitly. This option may be specified more
than once, in which case the filter masks are merged. If the
empty string is assigned, the filter is reset, all prior
assignments will have no effect. This does not affect
commands prefixed with "+".
Note that on systems supporting multiple ABIs (such as
x86/x86-64) it is recommended to turn off alternative ABIs
for services, so that they cannot be used to circumvent the
restrictions of this option. Specifically, it is recommended
to combine this option with SystemCallArchitectures=native or
similar.
Note that strict system call filters may impact execution and
error handling code paths of the service invocation.
Specifically, access to the execve() system call is required
for the execution of the service binary — if it is blocked
service invocation will necessarily fail. Also, if execution
of the service binary fails for some reason (for example:
missing service executable), the error handling logic might
require access to an additional set of system calls in order
to process and log this failure correctly. It might be
necessary to temporarily disable system call filters in order
to simplify debugging of such failures.
If you specify both types of this option (i.e. allow-listing
and deny-listing), the first encountered will take precedence
and will dictate the default action (termination or approval
of a system call). Then the next occurrences of this option
will add or delete the listed system calls from the set of
the filtered system calls, depending of its type and the
default action. (For example, if you have started with an
allow list rule for read() and write(), and right after it
add a deny list rule for write(), then write() will be
removed from the set.)
As the number of possible system calls is large, predefined
sets of system calls are provided. A set starts with "@"
character, followed by name of the set.
Table 4. Currently predefined system call sets
┌─────────────────┬──────────────────────────┐
│ Set │ Description │
├─────────────────┼──────────────────────────┤
│ @aio │ Asynchronous I/O (‐ │
│ │ io_setup(2), │
│ │ io_submit(2), and │
│ │ related calls) │
├─────────────────┼──────────────────────────┤
│ @basic-io │ System calls for basic │
│ │ I/O: reading, writing, │
│ │ seeking, file descriptor │
│ │ duplication and closing │
│ │ (read(2), write(2), and │
│ │ related calls) │
├─────────────────┼──────────────────────────┤
│ @chown │ Changing file ownership │
│ │ (chown(2), fchownat(2), │
│ │ and related calls) │
├─────────────────┼──────────────────────────┤
│ @clock │ System calls for │
│ │ changing the system │
│ │ clock (adjtimex(2), │
│ │ settimeofday(2), and │
│ │ related calls) │
├─────────────────┼──────────────────────────┤
│ @cpu-emulation │ System calls for CPU │
│ │ emulation functionality │
│ │ (vm86(2) and related │
│ │ calls) │
├─────────────────┼──────────────────────────┤
│ @debug │ Debugging, performance │
│ │ monitoring and tracing │
│ │ functionality (‐ │
│ │ ptrace(2), │
│ │ perf_event_open(2) and │
│ │ related calls) │
├─────────────────┼──────────────────────────┤
│ @file-system │ File system operations: │
│ │ opening, creating files │
│ │ and directories for read │
│ │ and write, renaming and │
│ │ removing them, reading │
│ │ file properties, or │
│ │ creating hard and │
│ │ symbolic links │
├─────────────────┼──────────────────────────┤
│ @io-event │ Event loop system calls │
│ │ (poll(2), select(2), │
│ │ epoll(7), eventfd(2) and │
│ │ related calls) │
├─────────────────┼──────────────────────────┤
│ @ipc │ Pipes, SysV IPC, POSIX │
│ │ Message Queues and other │
│ │ IPC (mq_overview(7), │
│ │ svipc(7)) │
├─────────────────┼──────────────────────────┤
│ @keyring │ Kernel keyring access (‐ │
│ │ keyctl(2) and related │
│ │ calls) │
├─────────────────┼──────────────────────────┤
│ @memlock │ Locking of memory in RAM │
│ │ (mlock(2), mlockall(2) │
│ │ and related calls) │
├─────────────────┼──────────────────────────┤
│ @module │ Loading and unloading of │
│ │ kernel modules (‐ │
│ │ init_module(2), │
│ │ delete_module(2) and │
│ │ related calls) │
├─────────────────┼──────────────────────────┤
│ @mount │ Mounting and unmounting │
│ │ of file systems (‐ │
│ │ mount(2), chroot(2), and │
│ │ related calls) │
├─────────────────┼──────────────────────────┤
│ @network-io │ Socket I/O (including │
│ │ local AF_UNIX): │
│ │ socket(7), unix(7) │
├─────────────────┼──────────────────────────┤
│ @obsolete │ Unusual, obsolete or │
│ │ unimplemented (‐ │
│ │ create_module(2), │
│ │ gtty(2), ...) │
├─────────────────┼──────────────────────────┤
│ @pkey │ System calls that deal │
│ │ with memory protection │
│ │ keys (pkeys(7)) │
├─────────────────┼──────────────────────────┤
│ @privileged │ All system calls which │
│ │ need super-user │
│ │ capabilities (‐ │
│ │ capabilities(7)) │
├─────────────────┼──────────────────────────┤
│ @process │ Process control, │
│ │ execution, namespacing │
│ │ operations (clone(2), │
│ │ kill(2), namespaces(7), │
│ │ ...) │
├─────────────────┼──────────────────────────┤
│ @raw-io │ Raw I/O port access (‐ │
│ │ ioperm(2), iopl(2), │
│ │ pciconfig_read(), ...) │
├─────────────────┼──────────────────────────┤
│ @reboot │ System calls for │
│ │ rebooting and reboot │
│ │ preparation (reboot(2), │
│ │ kexec(), ...) │
├─────────────────┼──────────────────────────┤
│ @resources │ System calls for │
│ │ changing resource │
│ │ limits, memory and │
│ │ scheduling parameters (‐ │
│ │ setrlimit(2), │
│ │ setpriority(2), ...) │
├─────────────────┼──────────────────────────┤
│ @sandbox │ System calls for │
│ │ sandboxing programs (‐ │
│ │ seccomp(2), Landlock │
│ │ system calls, ...) │
├─────────────────┼──────────────────────────┤
│ @setuid │ System calls for │
│ │ changing user ID and │
│ │ group ID credentials, (‐ │
│ │ setuid(2), setgid(2), │
│ │ setresuid(2), ...) │
├─────────────────┼──────────────────────────┤
│ @signal │ System calls for │
│ │ manipulating and │
│ │ handling process signals │
│ │ (signal(2), │
│ │ sigprocmask(2), ...) │
├─────────────────┼──────────────────────────┤
│ @swap │ System calls for │
│ │ enabling/disabling swap │
│ │ devices (swapon(2), │
│ │ swapoff(2)) │
├─────────────────┼──────────────────────────┤
│ @sync │ Synchronizing files and │
│ │ memory to disk (‐ │
│ │ fsync(2), msync(2), and │
│ │ related calls) │
├─────────────────┼──────────────────────────┤
│ @system-service │ A reasonable set of │
│ │ system calls used by │
│ │ common system services, │
│ │ excluding any special │
│ │ purpose calls. This is │
│ │ the recommended starting │
│ │ point for allow-listing │
│ │ system calls for system │
│ │ services, as it contains │
│ │ what is typically needed │
│ │ by system services, but │
│ │ excludes overly specific │
│ │ interfaces. For example, │
│ │ the following APIs are │
│ │ excluded: "@clock", │
│ │ "@mount", "@swap", │
│ │ "@reboot". │
├─────────────────┼──────────────────────────┤
│ @timer │ System calls for │
│ │ scheduling operations by │
│ │ time (alarm(2), │
│ │ timer_create(2), ...) │
├─────────────────┼──────────────────────────┤
│ @known │ All system calls defined │
│ │ by the kernel. This list │
│ │ is defined statically in │
│ │ systemd based on a │
│ │ kernel version that was │
│ │ available when this │
│ │ systemd version was │
│ │ released. It will become │
│ │ progressively more │
│ │ out-of-date as the │
│ │ kernel is updated. │
└─────────────────┴──────────────────────────┘
Note, that as new system calls are added to the kernel,
additional system calls might be added to the groups above.
Contents of the sets may also change between systemd
versions. In addition, the list of system calls depends on
the kernel version and architecture for which systemd was
compiled. Use systemd-analyze syscall-filter to list the
actual list of system calls in each filter.
Generally, allow-listing system calls (rather than
deny-listing) is the safer mode of operation. It is
recommended to enforce system call allow lists for all
long-running system services. Specifically, the following
lines are a relatively safe basic choice for the majority of
system services:
[Service]
SystemCallFilter=@system-service
SystemCallErrorNumber=EPERM
Note that various kernel system calls are defined
redundantly: there are multiple system calls for executing
the same operation. For example, the pidfd_send_signal()
system call may be used to execute operations similar to what
can be done with the older kill() system call, hence blocking
the latter without the former only provides weak protection.
Since new system calls are added regularly to the kernel as
development progresses, keeping system call deny lists
comprehensive requires constant work. It is thus recommended
to use allow-listing instead, which offers the benefit that
new system calls are by default implicitly blocked until the
allow list is updated.
Also note that a number of system calls are required to be
accessible for the dynamic linker to work. The dynamic linker
is required for running most regular programs (specifically:
all dynamic ELF binaries, which is how most distributions
build packaged programs). This means that blocking these
system calls (which include open(), openat() or mmap()) will
make most programs typically shipped with generic
distributions unusable.
It is recommended to combine the file system namespacing
related options with SystemCallFilter=~@mount, in order to
prohibit the unit's processes to undo the mappings.
Specifically these are the options PrivateTmp=,
PrivateDevices=, ProtectSystem=, ProtectHome=,
ProtectKernelTunables=, ProtectControlGroups=,
ProtectKernelLogs=, ProtectClock=, ReadOnlyPaths=,
InaccessiblePaths= and ReadWritePaths=.
Added in version 187.
SystemCallErrorNumber=
Takes an "errno" error number (between 1 and 4095) or errno
name such as EPERM, EACCES or EUCLEAN, to return when the
system call filter configured with SystemCallFilter= is
triggered, instead of terminating the process immediately.
See errno(3) for a full list of error codes. When this
setting is not used, or when the empty string or the special
setting "kill" is assigned, the process will be terminated
immediately when the filter is triggered.
Added in version 209.
SystemCallArchitectures=
Takes a space-separated list of architecture identifiers to
include in the system call filter. The known architecture
identifiers are the same as for ConditionArchitecture=
described in systemd.unit(5), as well as x32, mips64-n32,
mips64-le-n32, and the special identifier native. The special
identifier native implicitly maps to the native architecture
of the system (or more precisely: to the architecture the
system manager is compiled for). By default, this option is
set to the empty list, i.e. no filtering is applied.
If this setting is used, processes of this unit will only be
permitted to call native system calls, and system calls of
the specified architectures. For the purposes of this option,
the x32 architecture is treated as including x86-64 system
calls. However, this setting still fulfills its purpose, as
explained below, on x32.
System call filtering is not equally effective on all
architectures. For example, on x86 filtering of network
socket-related calls is not possible, due to ABI limitations
— a limitation that x86-64 does not have, however. On systems
supporting multiple ABIs at the same time — such as
x86/x86-64 — it is hence recommended to limit the set of
permitted system call architectures so that secondary ABIs
may not be used to circumvent the restrictions applied to the
native ABI of the system. In particular, setting
SystemCallArchitectures=native is a good choice for disabling
non-native ABIs.
System call architectures may also be restricted system-wide
via the SystemCallArchitectures= option in the global
configuration. See systemd-system.conf(5) for details.
Added in version 209.
SystemCallLog=
Takes a space-separated list of system call names. If this
setting is used, all system calls executed by the unit
processes for the listed ones will be logged. If the first
character of the list is "~", the effect is inverted: all
system calls except the listed system calls will be logged.
This feature makes use of the Secure Computing Mode 2
interfaces of the kernel ('seccomp filtering') and is useful
for auditing or setting up a minimal sandboxing environment.
This option may be specified more than once, in which case
the filter masks are merged. If the empty string is assigned,
the filter is reset, all prior assignments will have no
effect. This does not affect commands prefixed with "+".
Added in version 247.
Environment=
Sets environment variables for executed processes. Each line
is unquoted using the rules described in "Quoting" section in
systemd.syntax(7) and becomes a list of variable assignments.
If you need to assign a value containing spaces or the equals
sign to a variable, put quotes around the whole assignment.
Variable expansion is not performed inside the strings and
the "$" character has no special meaning. Specifier expansion
is performed, see the "Specifiers" section in
systemd.unit(5).
This option may be specified more than once, in which case
all listed variables will be set. If the same variable is
listed twice, the later setting will override the earlier
setting. If the empty string is assigned to this option, the
list of environment variables is reset, all prior assignments
have no effect.
The names of the variables can contain ASCII letters, digits,
and the underscore character. Variable names cannot be empty
or start with a digit. In variable values, most characters
are allowed, but non-printable characters are currently
rejected.
Example:
Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"
gives three variables "VAR1", "VAR2", "VAR3" with the values
"word1 word2", "word3", "$word 5 6".
See environ(7) for details about environment variables.
Note that environment variables are not suitable for passing
secrets (such as passwords, key material, ...) to service
processes. Environment variables set for a unit are exposed
to unprivileged clients via D-Bus IPC, and generally not
understood as being data that requires protection. Moreover,
environment variables are propagated down the process tree,
including across security boundaries (such as setuid/setgid
executables), and hence might leak to processes that should
not have access to the secret data. Use LoadCredential=,
LoadCredentialEncrypted= or SetCredentialEncrypted= (see
below) to pass data to unit processes securely.
EnvironmentFile=
Similar to Environment=, but reads the environment variables
from a text file. The text file should contain
newline-separated variable assignments. Empty lines, lines
without an "=" separator, or lines starting with ";" or "#"
will be ignored, which may be used for commenting. The file
must be encoded with UTF-8. Valid characters are unicode
scalar values[8] other than unicode noncharacters[9], U+0000
NUL, and U+FEFF unicode byte order mark[10]. Control codes
other than NUL are allowed.
In the file, an unquoted value after the "=" is parsed with
the same backslash-escape rules as POSIX shell unquoted
text[11], but unlike in a shell, interior whitespace is
preserved and quotes after the first non-whitespace character
are preserved. Leading and trailing whitespace (space, tab,
carriage return) is discarded, but interior whitespace within
the line is preserved verbatim. A line ending with a
backslash will be continued to the following one, with the
newline itself discarded. A backslash "\" followed by any
character other than newline will preserve the following
character, so that "\\" will become the value "\".
In the file, a "'"-quoted value after the "=" can span
multiple lines and contain any character verbatim other than
single quote, like POSIX shell single-quoted text[12]. No
backslash-escape sequences are recognized. Leading and
trailing whitespace outside of the single quotes is
discarded.
In the file, a """-quoted value after the "=" can span
multiple lines, and the same escape sequences are recognized
as in POSIX shell double-quoted text[13]. Backslash ("\")
followed by any of ""\`$" will preserve that character. A
backslash followed by newline is a line continuation, and the
newline itself is discarded. A backslash followed by any
other character is ignored; both the backslash and the
following character are preserved verbatim. Leading and
trailing whitespace outside of the double quotes is
discarded.
The argument passed should be an absolute filename or
wildcard expression, optionally prefixed with "-", which
indicates that if the file does not exist, it will not be
read and no error or warning message is logged. This option
may be specified more than once in which case all specified
files are read. If the empty string is assigned to this
option, the list of file to read is reset, all prior
assignments have no effect.
The files listed with this directive will be read shortly
before the process is executed (more specifically, after all
processes from a previous unit state terminated. This means
you can generate these files in one unit state, and read it
with this option in the next. The files are read from the
file system of the service manager, before any file system
changes like bind mounts take place).
Settings from these files override settings made with
Environment=. If the same variable is set twice from these
files, the files will be read in the order they are specified
and the later setting will override the earlier setting.
PassEnvironment=
Pass environment variables set for the system service manager
to executed processes. Takes a space-separated list of
variable names. This option may be specified more than once,
in which case all listed variables will be passed. If the
empty string is assigned to this option, the list of
environment variables to pass is reset, all prior assignments
have no effect. Variables specified that are not set for the
system manager will not be passed and will be silently
ignored. Note that this option is only relevant for the
system service manager, as system services by default do not
automatically inherit any environment variables set for the
service manager itself. However, in case of the user service
manager all environment variables are passed to the executed
processes anyway, hence this option is without effect for the
user service manager.
Variables set for invoked processes due to this setting are
subject to being overridden by those configured with
Environment= or EnvironmentFile=.
Example:
PassEnvironment=VAR1 VAR2 VAR3
passes three variables "VAR1", "VAR2", "VAR3" with the values
set for those variables in PID1.
See environ(7) for details about environment variables.
Added in version 228.
UnsetEnvironment=
Explicitly unset environment variable assignments that would
normally be passed from the service manager to invoked
processes of this unit. Takes a space-separated list of
variable names or variable assignments. This option may be
specified more than once, in which case all listed
variables/assignments will be unset. If the empty string is
assigned to this option, the list of environment
variables/assignments to unset is reset. If a variable
assignment is specified (that is: a variable name, followed
by "=", followed by its value), then any environment variable
matching this precise assignment is removed. If a variable
name is specified (that is a variable name without any
following "=" or value), then any assignment matching the
variable name, regardless of its value is removed. Note that
the effect of UnsetEnvironment= is applied as final step when
the environment list passed to executed processes is
compiled. That means it may undo assignments from any
configuration source, including assignments made through
Environment= or EnvironmentFile=, inherited from the system
manager's global set of environment variables, inherited via
PassEnvironment=, set by the service manager itself (such as
$NOTIFY_SOCKET and such), or set by a PAM module (in case
PAMName= is used).
See "Environment Variables in Spawned Processes" below for a
description of how those settings combine to form the
inherited environment. See environ(7) for general information
about environment variables.
Added in version 235.
StandardInput=
Controls where file descriptor 0 (STDIN) of the executed
processes is connected to. Takes one of null, tty, tty-force,
tty-fail, data, file:path, socket or fd:name.
If null is selected, standard input will be connected to
/dev/null, i.e. all read attempts by the process will result
in immediate EOF.
If tty is selected, standard input is connected to a TTY (as
configured by TTYPath=, see below) and the executed process
becomes the controlling process of the terminal. If the
terminal is already being controlled by another process, the
executed process waits until the current controlling process
releases the terminal.
tty-force is similar to tty, but the executed process is
forcefully and immediately made the controlling process of
the terminal, potentially removing previous controlling
processes from the terminal.
tty-fail is similar to tty, but if the terminal already has a
controlling process start-up of the executed process fails.
The data option may be used to configure arbitrary textual or
binary data to pass via standard input to the executed
process. The data to pass is configured via
StandardInputText=/StandardInputData= (see below). Note that
the actual file descriptor type passed (memory file, regular
file, UNIX pipe, ...) might depend on the kernel and
available privileges. In any case, the file descriptor is
read-only, and when read returns the specified data followed
by EOF.
The file:path option may be used to connect a specific file
system object to standard input. An absolute path following
the ":" character is expected, which may refer to a regular
file, a FIFO or special file. If an AF_UNIX socket in the
file system is specified, a stream socket is connected to it.
The latter is useful for connecting standard input of
processes to arbitrary system services.
The socket option is valid in socket-activated services only,
and requires the relevant socket unit file (see
systemd.socket(5) for details) to have Accept=yes set, or to
specify a single socket only. If this option is set, standard
input will be connected to the socket the service was
activated from, which is primarily useful for compatibility
with daemons designed for use with the traditional inetd(8)
socket activation daemon ($LISTEN_FDS (and related)
environment variables are not passed when socket value is
configured).
The fd:name option connects standard input to a specific,
named file descriptor provided by a socket unit. The name may
be specified as part of this option, following a ":"
character (e.g. "fd:foobar"). If no name is specified, the
name "stdin" is implied (i.e. "fd" is equivalent to
"fd:stdin"). At least one socket unit defining the specified
name must be provided via the Sockets= option, and the file
descriptor name may differ from the name of its containing
socket unit. If multiple matches are found, the first one
will be used. See FileDescriptorName= in systemd.socket(5)
for more details about named file descriptors and their
ordering.
This setting defaults to null, unless
StandardInputText=/StandardInputData= are set, in which case
it defaults to data.
StandardOutput=
Controls where file descriptor 1 (stdout) of the executed
processes is connected to. Takes one of inherit, null, tty,
journal, kmsg, journal+console, kmsg+console, file:path,
append:path, truncate:path, socket or fd:name.
inherit duplicates the file descriptor of standard input for
standard output.
null connects standard output to /dev/null, i.e. everything
written to it will be lost.
tty connects standard output to a tty (as configured via
TTYPath=, see below). If the TTY is used for output only, the
executed process will not become the controlling process of
the terminal, and will not fail or wait for other processes
to release the terminal.
journal connects standard output with the journal, which is
accessible via journalctl(1). Note that everything that is
written to kmsg (see below) is implicitly stored in the
journal as well, the specific option listed below is hence a
superset of this one. (Also note that any external,
additional syslog daemons receive their log data from the
journal, too, hence this is the option to use when logging
shall be processed with such a daemon.)
kmsg connects standard output with the kernel log buffer
which is accessible via dmesg(1), in addition to the journal.
The journal daemon might be configured to send all logs to
kmsg anyway, in which case this option is no different from
journal.
journal+console and kmsg+console work in a similar way as the
two options above but copy the output to the system console
as well.
The file:path option may be used to connect a specific file
system object to standard output. The semantics are similar
to the same option of StandardInput=, see above. If path
refers to a regular file on the filesystem, it is opened
(created if it doesn't exist yet using privileges of the user
executing the systemd process) for writing at the beginning
of the file, but without truncating it. If standard input and
output are directed to the same file path, it is opened only
once — for reading as well as writing — and duplicated. This
is particularly useful when the specified path refers to an
AF_UNIX socket in the file system, as in that case only a
single stream connection is created for both input and
output.
append:path is similar to file:path above, but it opens the
file in append mode.
truncate:path is similar to file:path above, but it truncates
the file when opening it. For units with multiple command
lines, e.g. Type=oneshot services with multiple ExecStart=,
or services with ExecCondition=, ExecStartPre= or
ExecStartPost=, the output file is reopened and therefore
re-truncated for each command line. If the output file is
truncated while another process still has the file open, e.g.
by an ExecReload= running concurrently with an ExecStart=,
and the other process continues writing to the file without
adjusting its offset, then the space between the file
pointers of the two processes may be filled with NUL bytes,
producing a sparse file. Thus, truncate:path is typically
only useful for units where only one process runs at a time,
such as services with a single ExecStart= and no
ExecStartPost=, ExecReload=, ExecStop= or similar.
socket connects standard output to a socket acquired via
socket activation. The semantics are similar to the same
option of StandardInput=, see above.
The fd:name option connects standard output to a specific,
named file descriptor provided by a socket unit. A name may
be specified as part of this option, following a ":"
character (e.g. "fd:foobar"). If no name is specified, the
name "stdout" is implied (i.e. "fd" is equivalent to
"fd:stdout"). At least one socket unit defining the specified
name must be provided via the Sockets= option, and the file
descriptor name may differ from the name of its containing
socket unit. If multiple matches are found, the first one
will be used. See FileDescriptorName= in systemd.socket(5)
for more details about named descriptors and their ordering.
If the standard output (or error output, see below) of a unit
is connected to the journal or the kernel log buffer, the
unit will implicitly gain a dependency of type After= on
systemd-journald.socket (also see the "Implicit Dependencies"
section above). Also note that in this case stdout (or
stderr, see below) will be an AF_UNIX stream socket, and not
a pipe or FIFO that can be reopened. This means when
executing shell scripts the construct echo "hello" >
/dev/stderr for writing text to stderr will not work. To
mitigate this use the construct echo "hello" >&2 instead,
which is mostly equivalent and avoids this pitfall.
If StandardInput= is set to one of tty, tty-force, tty-fail,
socket, or fd:name, this setting defaults to inherit.
In other cases, this setting defaults to the value set with
DefaultStandardOutput= in systemd-system.conf(5), which
defaults to journal. Note that setting this parameter might
result in additional dependencies to be added to the unit
(see above).
StandardError=
Controls where file descriptor 2 (stderr) of the executed
processes is connected to. The available options are
identical to those of StandardOutput=, with some exceptions:
if set to inherit the file descriptor used for standard
output is duplicated for standard error, while fd:name will
use a default file descriptor name of "stderr".
This setting defaults to the value set with
DefaultStandardError= in systemd-system.conf(5), which
defaults to inherit. Note that setting this parameter might
result in additional dependencies to be added to the unit
(see above).
StandardInputText=, StandardInputData=
Configures arbitrary textual or binary data to pass via file
descriptor 0 (STDIN) to the executed processes. These
settings have no effect unless StandardInput= is set to data
(which is the default if StandardInput= is not set otherwise,
but StandardInputText=/StandardInputData= is). Use this
option to embed process input data directly in the unit file.
StandardInputText= accepts arbitrary textual data. C-style
escapes for special characters as well as the usual
"%"-specifiers are resolved. Each time this setting is used
the specified text is appended to the per-unit data buffer,
followed by a newline character (thus every use appends a new
line to the end of the buffer). Note that leading and
trailing whitespace of lines configured with this option is
removed. If an empty line is specified the buffer is cleared
(hence, in order to insert an empty line, add an additional
"\n" to the end or beginning of a line).
StandardInputData= accepts arbitrary binary data, encoded in
Base64[14]. No escape sequences or specifiers are resolved.
Any whitespace in the encoded version is ignored during
decoding.
Note that StandardInputText= and StandardInputData= operate
on the same data buffer, and may be mixed in order to
configure both binary and textual data for the same input
stream. The textual or binary data is joined strictly in the
order the settings appear in the unit file. Assigning an
empty string to either will reset the data buffer.
Please keep in mind that in order to maintain readability
long unit file settings may be split into multiple lines, by
suffixing each line (except for the last) with a "\"
character (see systemd.unit(5) for details). This is
particularly useful for large data configured with these two
options. Example:
...
StandardInput=data
StandardInputData=V2XigLJyZSBubyBzdHJhbmdlcnMgdG8gbG92ZQpZb3Uga25vdyB0aGUgcnVsZXMgYW5kIHNvIGRv \
IEkKQSBmdWxsIGNvbW1pdG1lbnQncyB3aGF0IEnigLJtIHRoaW5raW5nIG9mCllvdSB3b3VsZG4n \
dCBnZXQgdGhpcyBmcm9tIGFueSBvdGhlciBndXkKSSBqdXN0IHdhbm5hIHRlbGwgeW91IGhvdyBJ \
J20gZmVlbGluZwpHb3R0YSBtYWtlIHlvdSB1bmRlcnN0YW5kCgpOZXZlciBnb25uYSBnaXZlIHlv \
dSB1cApOZXZlciBnb25uYSBsZXQgeW91IGRvd24KTmV2ZXIgZ29ubmEgcnVuIGFyb3VuZCBhbmQg \
ZGVzZXJ0IHlvdQpOZXZlciBnb25uYSBtYWtlIHlvdSBjcnkKTmV2ZXIgZ29ubmEgc2F5IGdvb2Ri \
eWUKTmV2ZXIgZ29ubmEgdGVsbCBhIGxpZSBhbmQgaHVydCB5b3UK
...
Added in version 236.
LogLevelMax=
Configures filtering by log level of log messages generated
by this unit. Takes a syslog log level, one of emerg (lowest
log level, only highest priority messages), alert, crit, err,
warning, notice, info, debug (highest log level, also lowest
priority messages). See syslog(3) for details. By default no
filtering is applied (i.e. the default maximum log level is
debug). Use this option to configure the logging system to
drop log messages of a specific service above the specified
level. For example, set LogLevelMax=info in order to turn off
debug logging of a particularly chatty unit. Note that the
configured level is applied to any log messages written by
any of the processes belonging to this unit, as well as any
log messages written by the system manager process (PID 1) in
reference to this unit, sent via any supported logging
protocol. The filtering is applied early in the logging
pipeline, before any kind of further processing is done.
Moreover, messages which pass through this filter
successfully might still be dropped by filters applied at a
later stage in the logging subsystem. For example,
MaxLevelStore= configured in journald.conf(5) might prohibit
messages of higher log levels to be stored on disk, even
though the per-unit LogLevelMax= permitted it to be
processed.
Added in version 236.
LogExtraFields=
Configures additional log metadata fields to include in all
log records generated by processes associated with this unit,
including systemd. This setting takes one or more journal
field assignments in the format "FIELD=VALUE" separated by
whitespace. See systemd.journal-fields(7) for details on the
journal field concept. Even though the underlying journal
implementation permits binary field values, this setting
accepts only valid UTF-8 values. To include space characters
in a journal field value, enclose the assignment in double
quotes ("). The usual specifiers are expanded in all
assignments (see below). Note that this setting is not only
useful for attaching additional metadata to log records of a
unit, but given that all fields and values are indexed may
also be used to implement cross-unit log record matching.
Assign an empty string to reset the list.
Note that this functionality is currently only available in
system services, not in per-user services.
Added in version 236.
LogRateLimitIntervalSec=, LogRateLimitBurst=
Configures the rate limiting that is applied to log messages
generated by this unit. If, in the time interval defined by
LogRateLimitIntervalSec=, more messages than specified in
LogRateLimitBurst= are logged by a service, all further
messages within the interval are dropped until the interval
is over. A message about the number of dropped messages is
generated. The time specification for
LogRateLimitIntervalSec= may be specified in the following
units: "s", "min", "h", "ms", "us". See systemd.time(7) for
details. The default settings are set by
RateLimitIntervalSec= and RateLimitBurst= configured in
journald.conf(5). Note that this only applies to log messages
that are processed by the logging subsystem, i.e. by
systemd-journald.service(8). This means that if you connect a
service's stderr directly to a file via
StandardOutput=file:... or a similar setting, the rate
limiting will not be applied to messages written that way
(but it will be enforced for messages generated via syslog(3)
and similar functions).
Added in version 240.
LogFilterPatterns=
Define an extended regular expression to filter log messages
based on the MESSAGE= field of the structured message. If the
first character of the pattern is "~", log entries matching
the pattern should be discarded. This option takes a single
pattern as an argument but can be used multiple times to
create a list of allowed and denied patterns. If the empty
string is assigned, the filter is reset, and all prior
assignments will have no effect.
Because the "~" character is used to define denied patterns,
it must be replaced with "\x7e" to allow a message starting
with "~". For example, "~foobar" would add a pattern matching
"foobar" to the deny list, while "\x7efoobar" would add a
pattern matching "~foobar" to the allow list.
Log messages are tested against denied patterns (if any),
then against allowed patterns (if any). If a log message
matches any of the denied patterns, it is discarded
immediately without considering allowed patterns. Remaining
log messages are tested against allowed patterns. Messages
matching against none of the allowed pattern are discarded.
If no allowed patterns are defined, then all messages are
processed directly after going through denied filters.
Filtering is based on the unit for which LogFilterPatterns=
is defined, meaning log messages coming from systemd(1) about
the unit are not taken into account. Filtered log messages
won't be forwarded to traditional syslog daemons, the kernel
log buffer (kmsg), the systemd console, or sent as wall
messages to all logged-in users.
Note that this functionality is currently only available in
system services, not in per-user services.
Added in version 253.
LogNamespace=
Run the unit's processes in the specified journal namespace.
Expects a short user-defined string identifying the
namespace. If not used the processes of the service are run
in the default journal namespace, i.e. their log stream is
collected and processed by systemd-journald.service. If this
option is used any log data generated by processes of this
unit (regardless if via the syslog(), journal native logging
or stdout/stderr logging) is collected and processed by an
instance of the systemd-journald@.service template unit,
which manages the specified namespace. The log data is stored
in a data store independent from the default log namespace's
data store. See systemd-journald.service(8) for details about
journal namespaces.
Internally, journal namespaces are implemented through Linux
mount namespacing and over-mounting the directory that
contains the relevant AF_UNIX sockets used for logging in the
unit's mount namespace. Since mount namespaces are used this
setting disconnects propagation of mounts from the unit's
processes to the host, similarly to how ReadOnlyPaths= and
similar settings describe above work. Journal namespaces may
hence not be used for services that need to establish mount
points on the host.
When this option is used the unit will automatically gain
ordering and requirement dependencies on the two socket units
associated with the systemd-journald@.service instance so
that they are automatically established prior to the unit
starting up. Note that when this option is used log output of
this service does not appear in the regular journalctl(1)
output, unless the --namespace= option is used.
This option is only available for system services and is not
supported for services running in per-user instances of the
service manager.
Added in version 245.
SyslogIdentifier=
Sets the process name ("syslog tag") to prefix log lines sent
to the logging system or the kernel log buffer with. If not
set, defaults to the process name of the executed process.
This option is only useful when StandardOutput= or
StandardError= are set to journal or kmsg (or to the same
settings in combination with +console) and only applies to
log messages written to stdout or stderr.
SyslogFacility=
Sets the syslog facility identifier to use when logging. One
of kern, user, mail, daemon, auth, syslog, lpr, news, uucp,
cron, authpriv, ftp, local0, local1, local2, local3, local4,
local5, local6 or local7. See syslog(3) for details. This
option is only useful when StandardOutput= or StandardError=
are set to journal or kmsg (or to the same settings in
combination with +console), and only applies to log messages
written to stdout or stderr. Defaults to daemon.
SyslogLevel=
The default syslog log level to use when logging to the
logging system or the kernel log buffer. One of emerg, alert,
crit, err, warning, notice, info, debug. See syslog(3) for
details. This option is only useful when StandardOutput= or
StandardError= are set to journal or kmsg (or to the same
settings in combination with +console), and only applies to
log messages written to stdout or stderr. Note that
individual lines output by executed processes may be prefixed
with a different log level which can be used to override the
default log level specified here. The interpretation of these
prefixes may be disabled with SyslogLevelPrefix=, see below.
For details, see sd-daemon(3). Defaults to info.
SyslogLevelPrefix=
Takes a boolean argument. If true and StandardOutput= or
StandardError= are set to journal or kmsg (or to the same
settings in combination with +console), log lines written by
the executed process that are prefixed with a log level will
be processed with this log level set but the prefix removed.
If set to false, the interpretation of these prefixes is
disabled and the logged lines are passed on as-is. This only
applies to log messages written to stdout or stderr. For
details about this prefixing see sd-daemon(3). Defaults to
true.
TTYPath=
Sets the terminal device node to use if standard input,
output, or error are connected to a TTY (see above). Defaults
to /dev/console.
TTYReset=
Reset the terminal device specified with TTYPath= before and
after execution. Defaults to "no".
TTYVHangup=
Disconnect all clients which have opened the terminal device
specified with TTYPath= before and after execution. Defaults
to "no".
TTYRows=, TTYColumns=
Configure the size of the TTY specified with TTYPath=. If
unset or set to the empty string, the kernel default is used.
Added in version 250.
TTYVTDisallocate=
If the terminal device specified with TTYPath= is a virtual
console terminal, try to deallocate the TTY before and after
execution. This ensures that the screen and scrollback buffer
is cleared. Defaults to "no".
LoadCredential=ID[:PATH], LoadCredentialEncrypted=ID[:PATH]
Pass a credential to the unit. Credentials are limited-size
binary or textual objects that may be passed to unit
processes. They are primarily used for passing cryptographic
keys (both public and private) or certificates, user account
information or identity information from host to services.
The data is accessible from the unit's processes via the file
system, at a read-only location that (if possible and
permitted) is backed by non-swappable memory. The data is
only accessible to the user associated with the unit, via the
User=/DynamicUser= settings (as well as the superuser). When
available, the location of credentials is exported as the
$CREDENTIALS_DIRECTORY environment variable to the unit's
processes.
The LoadCredential= setting takes a textual ID to use as name
for a credential plus a file system path, separated by a
colon. The ID must be a short ASCII string suitable as
filename in the filesystem, and may be chosen freely by the
user. If the specified path is absolute it is opened as
regular file and the credential data is read from it. If the
absolute path refers to an AF_UNIX stream socket in the file
system a connection is made to it (only once at unit
start-up) and the credential data read from the connection,
providing an easy IPC integration point for dynamically
transferring credentials from other services.
If the specified path is not absolute and itself qualifies as
valid credential identifier it is attempted to find a
credential that the service manager itself received under the
specified name — which may be used to propagate credentials
from an invoking environment (e.g. a container manager that
invoked the service manager) into a service. If no matching
system credential is found, the directories /etc/credstore/,
/run/credstore/ and /usr/lib/credstore/ are searched for
files under the credential's name — which hence are
recommended locations for credential data on disk. If
LoadCredentialEncrypted= is used /run/credstore.encrypted/,
/etc/credstore.encrypted/, and /usr/lib/credstore.encrypted/
are searched as well.
If the file system path is omitted it is chosen identical to
the credential name, i.e. this is a terse way to declare
credentials to inherit from the service manager into a
service. This option may be used multiple times, each time
defining an additional credential to pass to the unit.
Note that if the path is not specified or a valid credential
identifier is given, i.e. in the above two cases, a missing
credential is not considered fatal.
If an absolute path referring to a directory is specified,
every file in that directory (recursively) will be loaded as
a separate credential. The ID for each credential will be the
provided ID suffixed with "_$FILENAME" (e.g., "Key_file1").
When loading from a directory, symlinks will be ignored.
The contents of the file/socket may be arbitrary binary or
textual data, including newline characters and NUL bytes.
The LoadCredentialEncrypted= setting is identical to
LoadCredential=, except that the credential data is decrypted
and authenticated before being passed on to the executed
processes. Specifically, the referenced path should refer to
a file or socket with an encrypted credential, as implemented
by systemd-creds(1). This credential is loaded, decrypted,
authenticated and then passed to the application in plaintext
form, in the same way a regular credential specified via
LoadCredential= would be. A credential configured this way
may be symmetrically encrypted/authenticated with a secret
key derived from the system's TPM2 security chip, or with a
secret key stored in /var/lib/systemd/credentials.secret, or
with both. Using encrypted and authenticated credentials
improves security as credentials are not stored in plaintext
and only authenticated and decrypted into plaintext the
moment a service requiring them is started. Moreover,
credentials may be bound to the local hardware and
installations, so that they cannot easily be analyzed
offline, or be generated externally. When DevicePolicy= is
set to "closed" or "strict", or set to "auto" and
DeviceAllow= is set, or PrivateDevices= is set, then this
setting adds /dev/tpmrm0 with rw mode to DeviceAllow=. See
systemd.resource-control(5) for the details about
DevicePolicy= or DeviceAllow=.
Note that encrypted credentials targeted for services of the
per-user service manager must be encrypted with systemd-creds
encrypt --user, and those for the system service manager
without the --user switch. Encrypted credentials are always
targeted to a specific user or the system as a whole, and it
is ensured that per-user service managers cannot decrypt
secrets intended for the system or for other users.
The credential files/IPC sockets must be accessible to the
service manager, but don't have to be directly accessible to
the unit's processes: the credential data is read and copied
into separate, read-only copies for the unit that are
accessible to appropriately privileged processes. This is
particularly useful in combination with DynamicUser= as this
way privileged data can be made available to processes
running under a dynamic UID (i.e. not a previously known one)
without having to open up access to all users.
In order to reference the path a credential may be read from
within a ExecStart= command line use
"${CREDENTIALS_DIRECTORY}/mycred", e.g. "ExecStart=cat
${CREDENTIALS_DIRECTORY}/mycred". In order to reference the
path a credential may be read from within a Environment= line
use "%d/mycred", e.g. "Environment=MYCREDPATH=%d/mycred".
For system services the path may also be referenced as
"/run/credentials/UNITNAME" in cases where no interpolation
is possible, e.g. configuration files of software that does
not yet support credentials natively. $CREDENTIALS_DIRECTORY
is considered the primary interface to look for credentials,
though, since it also works for user services.
Currently, an accumulated credential size limit of 1 MB per
unit is enforced.
The service manager itself may receive system credentials
that can be propagated to services from a hosting container
manager or VM hypervisor. See the Container Interface[15]
documentation for details about the former. For the latter,
pass DMI/SMBIOS[16] OEM string table entries (field type 11)
with a prefix of "io.systemd.credential:" or
"io.systemd.credential.binary:". In both cases a key/value
pair separated by "=" is expected, in the latter case the
right-hand side is Base64 decoded when parsed (thus
permitting binary data to be passed in). Example qemu[17]
switch: "-smbios type=11,value=io.systemd.credential:xx=yy",
or "-smbios
type=11,value=io.systemd.credential.binary:rick=TmV2ZXIgR29ubmEgR2l2ZSBZb3UgVXA=".
Alternatively, use the qemu "fw_cfg" node
"opt/io.systemd.credentials/". Example qemu switch: "-fw_cfg
name=opt/io.systemd.credentials/mycred,string=supersecret".
They may also be passed from the UEFI firmware environment
via systemd-stub(7), from the initrd (see systemd(1)), or be
specified on the kernel command line using the
"systemd.set_credential=" and
"systemd.set_credential_binary=" switches (see systemd(1) –
this is not recommended since unprivileged userspace can read
the kernel command line).
If referencing an AF_UNIX stream socket to connect to, the
connection will originate from an abstract namespace socket,
that includes information about the unit and the credential
ID in its socket name. Use getpeername(2) to query this
information. The returned socket name is formatted as NUL
RANDOM "/unit/" UNIT "/" ID, i.e. a NUL byte (as required for
abstract namespace socket names), followed by a random string
(consisting of alphadecimal characters), followed by the
literal string "/unit/", followed by the requesting unit
name, followed by the literal character "/", followed by the
textual credential ID requested. Example:
"\0adf9d86b6eda275e/unit/foobar.service/credx" in case the
credential "credx" is requested for a unit "foobar.service".
This functionality is useful for using a single listening
socket to serve credentials to multiple consumers.
For further information see System and Service
Credentials[18] documentation.
Added in version 247.
ImportCredential=GLOB
Pass one or more credentials to the unit. Takes a credential
name for which we'll attempt to find a credential that the
service manager itself received under the specified name —
which may be used to propagate credentials from an invoking
environment (e.g. a container manager that invoked the
service manager) into a service. If the credential name is a
glob, all credentials matching the glob are passed to the
unit. Matching credentials are searched for in the system
credentials, the encrypted system credentials, and under
/etc/credstore/, /run/credstore/, /usr/lib/credstore/,
/run/credstore.encrypted/, /etc/credstore.encrypted/, and
/usr/lib/credstore.encrypted/ in that order. When multiple
credentials of the same name are found, the first one found
is used.
The globbing expression implements a restrictive subset of
glob(7): only a single trailing "*" wildcard may be
specified. Both "?" and "[]" wildcards are not permitted,
nor are "*" wildcards anywhere except at the end of the glob
expression.
When multiple credentials of the same name are found,
credentials found by LoadCredential= and
LoadCredentialEncrypted= take priority over credentials found
by ImportCredential=.
Added in version 254.
SetCredential=ID:VALUE, SetCredentialEncrypted=ID:VALUE
The SetCredential= setting is similar to LoadCredential= but
accepts a literal value to use as data for the credential,
instead of a file system path to read the data from. Do not
use this option for data that is supposed to be secret, as it
is accessible to unprivileged processes via IPC. It's only
safe to use this for user IDs, public key material and
similar non-sensitive data. For everything else use
LoadCredential=. In order to embed binary data into the
credential data use C-style escaping (i.e. "\n" to embed a
newline, or "\x00" to embed a NUL byte).
The SetCredentialEncrypted= setting is identical to
SetCredential= but expects an encrypted credential in literal
form as value. This allows embedding confidential credentials
securely directly in unit files. Use systemd-creds(1)' -p
switch to generate suitable SetCredentialEncrypted= lines
directly from plaintext credentials. For further details see
LoadCredentialEncrypted= above.
When multiple credentials of the same name are found,
credentials found by LoadCredential=,
LoadCredentialEncrypted= and ImportCredential= take priority
over credentials found by SetCredential=. As such,
SetCredential= will act as default if no credentials are
found by any of the former. In this case not being able to
retrieve the credential from the path specified in
LoadCredential= or LoadCredentialEncrypted= is not considered
fatal.
Added in version 247.
UtmpIdentifier=
Takes a four character identifier string for an utmp(5) and
wtmp entry for this service. This should only be set for
services such as getty implementations (such as agetty(8))
where utmp/wtmp entries must be created and cleared before
and after execution, or for services that shall be executed
as if they were run by a getty process (see below). If the
configured string is longer than four characters, it is
truncated and the terminal four characters are used. This
setting interprets %I style string replacements. This setting
is unset by default, i.e. no utmp/wtmp entries are created or
cleaned up for this service.
UtmpMode=
Takes one of "init", "login" or "user". If UtmpIdentifier= is
set, controls which type of utmp(5)/wtmp entries for this
service are generated. This setting has no effect unless
UtmpIdentifier= is set too. If "init" is set, only an
INIT_PROCESS entry is generated and the invoked process must
implement a getty-compatible utmp/wtmp logic. If "login" is
set, first an INIT_PROCESS entry, followed by a LOGIN_PROCESS
entry is generated. In this case, the invoked process must
implement a login(1)-compatible utmp/wtmp logic. If "user" is
set, first an INIT_PROCESS entry, then a LOGIN_PROCESS entry
and finally a USER_PROCESS entry is generated. In this case,
the invoked process may be any process that is suitable to be
run as session leader. Defaults to "init".
Added in version 225.
Processes started by the service manager are executed with an
environment variable block assembled from multiple sources.
Processes started by the system service manager generally do not
inherit environment variables set for the service manager itself
(but this may be altered via PassEnvironment=), but processes
started by the user service manager instances generally do
inherit all environment variables set for the service manager
itself.
For each invoked process the list of environment variables set is
compiled from the following sources:
• Variables globally configured for the service manager, using
the DefaultEnvironment= setting in systemd-system.conf(5),
the kernel command line option systemd.setenv= understood by
systemd(1), or via systemctl(1) set-environment verb.
• Variables defined by the service manager itself (see the list
below).
• Variables set in the service manager's own environment
variable block (subject to PassEnvironment= for the system
service manager).
• Variables set via Environment= in the unit file.
• Variables read from files specified via EnvironmentFile= in
the unit file.
• Variables set by any PAM modules in case PAMName= is in
effect, cf. pam_env(8).
If the same environment variable is set by multiple of these
sources, the later source — according to the order of the list
above — wins. Note that as the final step all variables listed in
UnsetEnvironment= are removed from the compiled environment
variable list, immediately before it is passed to the executed
process.
The general philosophy is to expose a small curated list of
environment variables to processes. Services started by the
system manager (PID 1) will be started, without additional
service-specific configuration, with just a few environment
variables. The user manager inherits environment variables as any
other system service, but in addition may receive additional
environment variables from PAM, and, typically, additional
imported variables when the user starts a graphical session. It
is recommended to keep the environment blocks in both the system
and user managers lean. Importing all variables inherited by the
graphical session or by one of the user shells is strongly
discouraged.
Hint: systemd-run -P env and systemd-run --user -P env print the
effective system and user service environment blocks.
Environment Variables Set or Propagated by the Service Manager
The following environment variables are propagated by the service
manager or generated internally for each invoked process:
$PATH
Colon-separated list of directories to use when launching
executables. systemd uses a fixed value of
"/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin" in the
system manager. In case of the user manager, a different path
may be configured by the distribution. It is recommended to
not rely on the order of entries, and have only one program
with a given name in $PATH.
Added in version 208.
$LANG
Locale. Can be set in locale.conf(5) or on the kernel command
line (see systemd(1) and kernel-command-line(7)).
Added in version 208.
$USER, $LOGNAME, $HOME, $SHELL
User name (twice), home directory, and the login shell.
$USER is set unconditionally, while $HOME, $LOGNAME, and
$SHELL are only set for the units that have User= set and
SetLoginEnvironment= unset or set to true. For user services,
these variables are typically inherited from the user manager
itself. See passwd(5).
Added in version 208.
$INVOCATION_ID
Contains a randomized, unique 128-bit ID identifying each
runtime cycle of the unit, formatted as 32 character
hexadecimal string. A new ID is assigned each time the unit
changes from an inactive state into an activating or active
state, and may be used to identify this specific runtime
cycle, in particular in data stored offline, such as the
journal. The same ID is passed to all processes run as part
of the unit.
Added in version 232.
$XDG_RUNTIME_DIR
The directory to use for runtime objects (such as IPC
objects) and volatile state. Set for all services run by the
user systemd instance, as well as any system services that
use PAMName= with a PAM stack that includes pam_systemd. See
below and pam_systemd(8) for more information.
Added in version 208.
$RUNTIME_DIRECTORY, $STATE_DIRECTORY, $CACHE_DIRECTORY,
$LOGS_DIRECTORY, $CONFIGURATION_DIRECTORY
Absolute paths to the directories defined with
RuntimeDirectory=, StateDirectory=, CacheDirectory=,
LogsDirectory=, and ConfigurationDirectory= when those
settings are used.
Added in version 244.
$CREDENTIALS_DIRECTORY
An absolute path to the per-unit directory with credentials
configured via
ImportCredential=/LoadCredential=/SetCredential=. The
directory is marked read-only and is placed in unswappable
memory (if supported and permitted), and is only accessible
to the UID associated with the unit via User= or DynamicUser=
(and the superuser).
Added in version 247.
$MAINPID
The PID of the unit's main process if it is known. This is
only set for control processes as invoked by ExecReload= and
similar.
Added in version 209.
$MANAGERPID
The PID of the user systemd instance, set for processes
spawned by it.
Added in version 208.
$LISTEN_FDS, $LISTEN_PID, $LISTEN_FDNAMES
Information about file descriptors passed to a service for
socket activation. See sd_listen_fds(3).
Added in version 208.
$NOTIFY_SOCKET
The socket sd_notify() talks to. See sd_notify(3).
Added in version 229.
$WATCHDOG_PID, $WATCHDOG_USEC
Information about watchdog keep-alive notifications. See
sd_watchdog_enabled(3).
Added in version 229.
$SYSTEMD_EXEC_PID
The PID of the unit process (e.g. process invoked by
ExecStart=). The child process can use this information to
determine whether the process is directly invoked by the
service manager or indirectly as a child of another process
by comparing this value with the current PID (similarly to
the scheme used in sd_listen_fds(3) with $LISTEN_PID and
$LISTEN_FDS).
Added in version 248.
$TERM
Terminal type, set only for units connected to a terminal
(StandardInput=tty, StandardOutput=tty, or
StandardError=tty). See termcap(5).
Added in version 209.
$LOG_NAMESPACE
Contains the name of the selected logging namespace when the
LogNamespace= service setting is used.
Added in version 246.
$JOURNAL_STREAM
If the standard output or standard error output of the
executed processes are connected to the journal (for example,
by setting StandardError=journal) $JOURNAL_STREAM contains
the device and inode numbers of the connection file
descriptor, formatted in decimal, separated by a colon (":").
This permits invoked processes to safely detect whether their
standard output or standard error output are connected to the
journal. The device and inode numbers of the file descriptors
should be compared with the values set in the environment
variable to determine whether the process output is still
connected to the journal. Note that it is generally not
sufficient to only check whether $JOURNAL_STREAM is set at
all as services might invoke external processes replacing
their standard output or standard error output, without
unsetting the environment variable.
If both standard output and standard error of the executed
processes are connected to the journal via a stream socket,
this environment variable will contain information about the
standard error stream, as that's usually the preferred
destination for log data. (Note that typically the same
stream is used for both standard output and standard error,
hence very likely the environment variable contains device
and inode information matching both stream file descriptors.)
This environment variable is primarily useful to allow
services to optionally upgrade their used log protocol to the
native journal protocol (using sd_journal_print(3) and other
functions) if their standard output or standard error output
is connected to the journal anyway, thus enabling delivery of
structured metadata along with logged messages.
Added in version 231.
$SERVICE_RESULT
Only used for the service unit type. This environment
variable is passed to all ExecStop= and ExecStopPost=
processes, and encodes the service "result". Currently, the
following values are defined:
Table 5. Defined $SERVICE_RESULT values
┌───────────────────┬──────────────────────────┐
│ Value │ Meaning │
├───────────────────┼──────────────────────────┤
│ "success" │ The service ran │
│ │ successfully and exited │
│ │ cleanly. │
├───────────────────┼──────────────────────────┤
│ "protocol" │ A protocol violation │
│ │ occurred: the service │
│ │ did not take the steps │
│ │ required by its unit │
│ │ configuration │
│ │ (specifically what is │
│ │ configured in its Type= │
│ │ setting). │
├───────────────────┼──────────────────────────┤
│ "timeout" │ One of the steps timed │
│ │ out. │
├───────────────────┼──────────────────────────┤
│ "exit-code" │ Service process exited │
│ │ with a non-zero exit │
│ │ code; see $EXIT_CODE │
│ │ below for the actual │
│ │ exit code returned. │
├───────────────────┼──────────────────────────┤
│ "signal" │ A service process was │
│ │ terminated abnormally by │
│ │ a signal, without │
│ │ dumping core. See │
│ │ $EXIT_CODE below for the │
│ │ actual signal causing │
│ │ the termination. │
├───────────────────┼──────────────────────────┤
│ "core-dump" │ A service process │
│ │ terminated abnormally │
│ │ with a signal and dumped │
│ │ core. See $EXIT_CODE │
│ │ below for the signal │
│ │ causing the termination. │
├───────────────────┼──────────────────────────┤
│ "watchdog" │ Watchdog keep-alive ping │
│ │ was enabled for the │
│ │ service, but the │
│ │ deadline was missed. │
├───────────────────┼──────────────────────────┤
│ "exec-condition" │ Service did not run │
│ │ because ExecCondition= │
│ │ failed. │
├───────────────────┼──────────────────────────┤
│ "oom-kill" │ A service process was │
│ │ terminated by the │
│ │ Out-Of-Memory (OOM) │
│ │ killer. │
├───────────────────┼──────────────────────────┤
│ "start-limit-hit" │ A start limit was │
│ │ defined for the unit and │
│ │ it was hit, causing the │
│ │ unit to fail to start. │
│ │ See systemd.unit(5)'s │
│ │ StartLimitIntervalSec= │
│ │ and StartLimitBurst= for │
│ │ details. │
├───────────────────┼──────────────────────────┤
│ "resources" │ A catch-all condition in │
│ │ case a system operation │
│ │ failed. │
└───────────────────┴──────────────────────────┘
This environment variable is useful to monitor failure or
successful termination of a service. Even though this
variable is available in both ExecStop= and ExecStopPost=, it
is usually a better choice to place monitoring tools in the
latter, as the former is only invoked for services that
managed to start up correctly, and the latter covers both
services that failed during their start-up and those which
failed during their runtime.
Added in version 232.
$EXIT_CODE, $EXIT_STATUS
Only defined for the service unit type. These environment
variables are passed to all ExecStop=, ExecStopPost=
processes and contain exit status/code information of the
main process of the service. For the precise definition of
the exit code and status, see wait(2). $EXIT_CODE is one of
"exited", "killed", "dumped". $EXIT_STATUS contains the
numeric exit code formatted as string if $EXIT_CODE is
"exited", and the signal name in all other cases. Note that
these environment variables are only set if the service
manager succeeded to start and identify the main process of
the service.
Table 6. Summary of possible service result variable values
┌───────────────────┬──────────────────┬──────────────────┐
│ $SERVICE_RESULT │ $EXIT_CODE │ $EXIT_STATUS │
├───────────────────┼──────────────────┼──────────────────┤
│ "success" │ "killed" │ "HUP", "INT", │
│ │ │ "TERM", "PIPE" │
│ ├──────────────────┼──────────────────┤
│ │ "exited" │ "0" │
├───────────────────┼──────────────────┼──────────────────┤
│ "protocol" │ not set │ not set │
│ ├──────────────────┼──────────────────┤
│ │ "exited" │ "0" │
├───────────────────┼──────────────────┼──────────────────┤
│ "timeout" │ "killed" │ "TERM", "KILL" │
│ ├──────────────────┼──────────────────┤
│ │ "exited" │ "0", "1", "2", │
│ │ │ "3", ..., "255" │
├───────────────────┼──────────────────┼──────────────────┤
│ "exit-code" │ "exited" │ "1", "2", "3", │
│ │ │ ..., "255" │
├───────────────────┼──────────────────┼──────────────────┤
│ "signal" │ "killed" │ "HUP", "INT", │
│ │ │ "KILL", ... │
├───────────────────┼──────────────────┼──────────────────┤
│ "core-dump" │ "dumped" │ "ABRT", "SEGV", │
│ │ │ "QUIT", ... │
├───────────────────┼──────────────────┼──────────────────┤
│ "watchdog" │ "dumped" │ "ABRT" │
│ ├──────────────────┼──────────────────┤
│ │ "killed" │ "TERM", "KILL" │
│ ├──────────────────┼──────────────────┤
│ │ "exited" │ "0", "1", "2", │
│ │ │ "3", ..., "255" │
├───────────────────┼──────────────────┼──────────────────┤
│ "exec-condition" │ "exited" │ "1", "2", "3", │
│ │ │ "4", ..., "254" │
├───────────────────┼──────────────────┼──────────────────┤
│ "oom-kill" │ "killed" │ "TERM", "KILL" │
├───────────────────┼──────────────────┼──────────────────┤
│ "start-limit-hit" │ not set │ not set │
├───────────────────┼──────────────────┼──────────────────┤
│ "resources" │ any of the above │ any of the above │
├───────────────────┴──────────────────┴──────────────────┤
│ Note: the process may be also terminated by a signal │
│ not sent by systemd. In particular the process may │
│ send an arbitrary signal to itself in a handler for │
│ any of the non-maskable signals. Nevertheless, in the │
│ "timeout" and "watchdog" rows above only the signals │
│ that systemd sends have been included. Moreover, using │
│ SuccessExitStatus= additional exit statuses may be │
│ declared to indicate clean termination, which is not │
│ reflected by this table. │
└─────────────────────────────────────────────────────────┘
Added in version 232.
$MONITOR_SERVICE_RESULT, $MONITOR_EXIT_CODE,
$MONITOR_EXIT_STATUS, $MONITOR_INVOCATION_ID, $MONITOR_UNIT
Only defined for the service unit type. Those environment
variables are passed to all ExecStart= and ExecStartPre=
processes which run in services triggered by OnFailure= or
OnSuccess= dependencies.
Variables $MONITOR_SERVICE_RESULT, $MONITOR_EXIT_CODE and
$MONITOR_EXIT_STATUS take the same values as for ExecStop=
and ExecStopPost= processes. Variables $MONITOR_INVOCATION_ID
and $MONITOR_UNIT are set to the invocation id and unit name
of the service which triggered the dependency.
Note that when multiple services trigger the same unit, those
variables will be not be passed. Consider using a template
handler unit for that case instead:
"OnFailure=handler@%n.service" for non-templated units, or
"OnFailure=handler@%p-%i.service" for templated units.
Added in version 251.
$PIDFILE
The path to the configured PID file, in case the process is
forked off on behalf of a service that uses the PIDFile=
setting, see systemd.service(5) for details. Service code may
use this environment variable to automatically generate a PID
file at the location configured in the unit file. This field
is set to an absolute path in the file system.
Added in version 242.
$REMOTE_ADDR, $REMOTE_PORT
If this is a unit started via per-connection socket
activation (i.e. via a socket unit with Accept=yes), these
environment variables contain information about the remote
peer of the socket connection.
For IPv4 and IPv6 connections, $REMOTE_ADDR contains the IP
address, and $REMOTE_PORT contains the port number of the
remote peer.
For AF_UNIX socket connections, $REMOTE_ADDR contains either
the remote socket's file system path starting with a slash
("/"), its address in the abstract namespace starting with an
at symbol ("@"), or is unset in case of an unnamed socket.
$REMOTE_PORT is not set for AF_UNIX sockets.
Added in version 254.
$TRIGGER_UNIT, $TRIGGER_PATH, $TRIGGER_TIMER_REALTIME_USEC,
$TRIGGER_TIMER_MONOTONIC_USEC
If the unit was activated dynamically (e.g.: a corresponding
path unit or timer unit), the unit that triggered it and
other type-dependent information will be passed via these
variables. Note that this information is provided in a
best-effort way. For example, multiple triggers happening one
after another will be coalesced and only one will be
reported, with no guarantee as to which one it will be.
Because of this, in most cases this variable will be
primarily informational, i.e. useful for debugging purposes,
is lossy, and should not be relied upon to propagate a
comprehensive reason for activation.
Added in version 252.
$MEMORY_PRESSURE_WATCH, $MEMORY_PRESSURE_WRITE
If memory pressure monitoring is enabled for this service
unit, the path to watch and the data to write into it. See
Memory Pressure Handling[19] for details about these
variables and the service protocol data they convey.
Added in version 254.
$FDSTORE
The maximum number of file descriptors that may be stored in
the manager for the service. This variable is set when the
file descriptor store is enabled for the service, i.e.
FileDescriptorStoreMax= is set to a non-zero value (see
systemd.service(5) for details). Applications may check this
environment variable before sending file descriptors to the
service manager via sd_pid_notify_with_fds(3).
Added in version 254.
For system services, when PAMName= is enabled and pam_systemd is
part of the selected PAM stack, additional environment variables
defined by systemd may be set for services. Specifically, these
are $XDG_SEAT, $XDG_VTNR, see pam_systemd(8) for details.
When invoking a unit process the service manager possibly fails
to apply the execution parameters configured with the settings
above. In that case the already created service process will exit
with a non-zero exit code before the configured command line is
executed. (Or in other words, the child process possibly exits
with these error codes, after having been created by the fork(2)
system call, but before the matching execve(2) system call is
called.) Specifically, exit codes defined by the C library, by
the LSB specification and by the systemd service manager itself
are used.
The following basic service exit codes are defined by the C
library.
Table 7. Basic C library exit codes
┌───────────┬───────────────┬────────────────────┐
│ Exit Code │ Symbolic Name │ Description │
├───────────┼───────────────┼────────────────────┤
│ 0 │ EXIT_SUCCESS │ Generic success │
│ │ │ code. │
├───────────┼───────────────┼────────────────────┤
│ 1 │ EXIT_FAILURE │ Generic failure or │
│ │ │ unspecified error. │
└───────────┴───────────────┴────────────────────┘
The following service exit codes are defined by the LSB
specification[20].
Table 8. LSB service exit codes
┌───────────┬──────────────────────┬────────────────────┐
│ Exit Code │ Symbolic Name │ Description │
├───────────┼──────────────────────┼────────────────────┤
│ 2 │ EXIT_INVALIDARGUMENT │ Invalid or excess │
│ │ │ arguments. │
├───────────┼──────────────────────┼────────────────────┤
│ 3 │ EXIT_NOTIMPLEMENTED │ Unimplemented │
│ │ │ feature. │
├───────────┼──────────────────────┼────────────────────┤
│ 4 │ EXIT_NOPERMISSION │ The user has │
│ │ │ insufficient │
│ │ │ privileges. │
├───────────┼──────────────────────┼────────────────────┤
│ 5 │ EXIT_NOTINSTALLED │ The program is not │
│ │ │ installed. │
├───────────┼──────────────────────┼────────────────────┤
│ 6 │ EXIT_NOTCONFIGURED │ The program is not │
│ │ │ configured. │
├───────────┼──────────────────────┼────────────────────┤
│ 7 │ EXIT_NOTRUNNING │ The program is not │
│ │ │ running. │
└───────────┴──────────────────────┴────────────────────┘
The LSB specification suggests that error codes 200 and above are
reserved for implementations. Some of them are used by the
service manager to indicate problems during process invocation:
Table 9. systemd-specific exit codes
┌───────────┬──────────────────────────────┬─────────────────────────────────────────────┐
│ Exit Code │ Symbolic Name │ Description │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 200 │ EXIT_CHDIR │ Changing to the │
│ │ │ requested working │
│ │ │ directory failed. │
│ │ │ See │
│ │ │ WorkingDirectory= │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 201 │ EXIT_NICE │ Failed to set up │
│ │ │ process scheduling │
│ │ │ priority (nice │
│ │ │ level). See Nice= │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 202 │ EXIT_FDS │ Failed to close │
│ │ │ unwanted file │
│ │ │ descriptors, or to │
│ │ │ adjust passed file │
│ │ │ descriptors. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 203 │ EXIT_EXEC │ The actual process │
│ │ │ execution failed │
│ │ │ (specifically, the │
│ │ │ execve(2) system │
│ │ │ call). Most likely │
│ │ │ this is caused by │
│ │ │ a missing or │
│ │ │ non-accessible │
│ │ │ executable file. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 204 │ EXIT_MEMORY │ Failed to perform │
│ │ │ an action due to │
│ │ │ memory shortage. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 205 │ EXIT_LIMITS │ Failed to adjust │
│ │ │ resource limits. │
│ │ │ See LimitCPU= and │
│ │ │ related settings │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 206 │ EXIT_OOM_ADJUST │ Failed to adjust │
│ │ │ the OOM setting. │
│ │ │ See │
│ │ │ OOMScoreAdjust= │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 207 │ EXIT_SIGNAL_MASK │ Failed to set │
│ │ │ process signal │
│ │ │ mask. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 208 │ EXIT_STDIN │ Failed to set up │
│ │ │ standard input. │
│ │ │ See StandardInput= │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 209 │ EXIT_STDOUT │ Failed to set up │
│ │ │ standard output. │
│ │ │ See │
│ │ │ StandardOutput= │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 210 │ EXIT_CHROOT │ Failed to change │
│ │ │ root directory (‐ │
│ │ │ chroot(2)). See │
│ │ │ RootDirectory=/RootImage= │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 211 │ EXIT_IOPRIO │ Failed to set up IO │
│ │ │ scheduling priority. See │
│ │ │ IOSchedulingClass=/IOSchedulingPriority= │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 212 │ EXIT_TIMERSLACK │ Failed to set up timer slack. See │
│ │ │ TimerSlackNSec= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 213 │ EXIT_SECUREBITS │ Failed to set process secure bits. See │
│ │ │ SecureBits= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 214 │ EXIT_SETSCHEDULER │ Failed to set up CPU scheduling. See │
│ │ │ CPUSchedulingPolicy=/CPUSchedulingPriority= │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 215 │ EXIT_CPUAFFINITY │ Failed to set up CPU affinity. See │
│ │ │ CPUAffinity= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 216 │ EXIT_GROUP │ Failed to determine or change group │
│ │ │ credentials. See │
│ │ │ Group=/SupplementaryGroups= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 217 │ EXIT_USER │ Failed to determine or change user │
│ │ │ credentials, or to set up user namespacing. │
│ │ │ See User=/PrivateUsers= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 218 │ EXIT_CAPABILITIES │ Failed to drop capabilities, or apply │
│ │ │ ambient capabilities. See │
│ │ │ CapabilityBoundingSet=/AmbientCapabilities= │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 219 │ EXIT_CGROUP │ Setting up the service control group │
│ │ │ failed. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 220 │ EXIT_SETSID │ Failed to create new process session. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 221 │ EXIT_CONFIRM │ Execution has been cancelled by the user. │
│ │ │ See the systemd.confirm_spawn= kernel │
│ │ │ command line setting on │
│ │ │ kernel-command-line(7) for details. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 222 │ EXIT_STDERR │ Failed to set up standard error output. See │
│ │ │ StandardError= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 224 │ EXIT_PAM │ Failed to set up PAM session. See PAMName= │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 225 │ EXIT_NETWORK │ Failed to set up network namespacing. See │
│ │ │ PrivateNetwork= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 226 │ EXIT_NAMESPACE │ Failed to set up mount, UTS, or IPC │
│ │ │ namespacing. See ReadOnlyPaths=, │
│ │ │ ProtectHostname=, PrivateIPC=, and related │
│ │ │ settings above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 227 │ EXIT_NO_NEW_PRIVILEGES │ Failed to disable new privileges. See │
│ │ │ NoNewPrivileges=yes above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 228 │ EXIT_SECCOMP │ Failed to apply system call filters. See │
│ │ │ SystemCallFilter= and related settings │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 229 │ EXIT_SELINUX_CONTEXT │ Determining or changing SELinux context │
│ │ │ failed. See SELinuxContext= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 230 │ EXIT_PERSONALITY │ Failed to set up an execution domain │
│ │ │ (personality). See Personality= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 231 │ EXIT_APPARMOR_PROFILE │ Failed to prepare changing AppArmor │
│ │ │ profile. See AppArmorProfile= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 232 │ EXIT_ADDRESS_FAMILIES │ Failed to restrict address families. See │
│ │ │ RestrictAddressFamilies= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 233 │ EXIT_RUNTIME_DIRECTORY │ Setting up runtime directory failed. See │
│ │ │ RuntimeDirectory= and related settings │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 235 │ EXIT_CHOWN │ Failed to adjust socket ownership. Used for │
│ │ │ socket units only. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 236 │ EXIT_SMACK_PROCESS_LABEL │ Failed to set SMACK label. See │
│ │ │ SmackProcessLabel= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 237 │ EXIT_KEYRING │ Failed to set up kernel keyring. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 238 │ EXIT_STATE_DIRECTORY │ Failed to set up unit's state directory. │
│ │ │ See StateDirectory= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 239 │ EXIT_CACHE_DIRECTORY │ Failed to set up unit's cache directory. │
│ │ │ See CacheDirectory= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 240 │ EXIT_LOGS_DIRECTORY │ Failed to set up unit's logging directory. │
│ │ │ See LogsDirectory= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 241 │ EXIT_CONFIGURATION_DIRECTORY │ Failed to set up unit's configuration │
│ │ │ directory. See ConfigurationDirectory= │
│ │ │ above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 242 │ EXIT_NUMA_POLICY │ Failed to set up unit's NUMA memory policy. │
│ │ │ See NUMAPolicy= and NUMAMask= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 243 │ EXIT_CREDENTIALS │ Failed to set up unit's credentials. See │
│ │ │ ImportCredential=, LoadCredential= and │
│ │ │ SetCredential= above. │
├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
│ 245 │ EXIT_BPF │ Failed to apply BPF restrictions. See │
│ │ │ RestrictFileSystems= above. │
└───────────┴──────────────────────────────┴─────────────────────────────────────────────┘
Finally, the BSD operating systems define a set of exit codes,
typically defined on Linux systems too:
Table 10. BSD exit codes
┌───────────┬────────────────┬────────────────────┐
│ Exit Code │ Symbolic Name │ Description │
├───────────┼────────────────┼────────────────────┤
│ 64 │ EX_USAGE │ Command line usage │
│ │ │ error │
├───────────┼────────────────┼────────────────────┤
│ 65 │ EX_DATAERR │ Data format error │
├───────────┼────────────────┼────────────────────┤
│ 66 │ EX_NOINPUT │ Cannot open input │
├───────────┼────────────────┼────────────────────┤
│ 67 │ EX_NOUSER │ Addressee unknown │
├───────────┼────────────────┼────────────────────┤
│ 68 │ EX_NOHOST │ Host name unknown │
├───────────┼────────────────┼────────────────────┤
│ 69 │ EX_UNAVAILABLE │ Service │
│ │ │ unavailable │
├───────────┼────────────────┼────────────────────┤
│ 70 │ EX_SOFTWARE │ internal software │
│ │ │ error │
├───────────┼────────────────┼────────────────────┤
│ 71 │ EX_OSERR │ System error │
│ │ │ (e.g., can't fork) │
├───────────┼────────────────┼────────────────────┤
│ 72 │ EX_OSFILE │ Critical OS file │
│ │ │ missing │
├───────────┼────────────────┼────────────────────┤
│ 73 │ EX_CANTCREAT │ Can't create │
│ │ │ (user) output file │
├───────────┼────────────────┼────────────────────┤
│ 74 │ EX_IOERR │ Input/output error │
├───────────┼────────────────┼────────────────────┤
│ 75 │ EX_TEMPFAIL │ Temporary failure; │
│ │ │ user is invited to │
│ │ │ retry │
├───────────┼────────────────┼────────────────────┤
│ 76 │ EX_PROTOCOL │ Remote error in │
│ │ │ protocol │
├───────────┼────────────────┼────────────────────┤
│ 77 │ EX_NOPERM │ Permission denied │
├───────────┼────────────────┼────────────────────┤
│ 78 │ EX_CONFIG │ Configuration │
│ │ │ error │
└───────────┴────────────────┴────────────────────┘
Example 3. $MONITOR_* usage
A service myfailer.service which can trigger an OnFailure=
dependency.
[Unit]
Description=Service which can trigger an OnFailure= dependency
OnFailure=myhandler.service
[Service]
ExecStart=/bin/myprogram
A service mysuccess.service which can trigger an OnSuccess=
dependency.
[Unit]
Description=Service which can trigger an OnSuccess= dependency
OnSuccess=myhandler.service
[Service]
ExecStart=/bin/mysecondprogram
A service myhandler.service which can be triggered by any of the
above services.
[Unit]
Description=Acts on service failing or succeeding
[Service]
ExecStart=/bin/bash -c "echo $MONITOR_SERVICE_RESULT $MONITOR_EXIT_CODE $MONITOR_EXIT_STATUS $MONITOR_INVOCATION_ID $MONITOR_UNIT"
If myfailer.service were to run and exit in failure, then
myhandler.service would be triggered and the monitor variables
would be set as follows:
MONITOR_SERVICE_RESULT=exit-code
MONITOR_EXIT_CODE=exited
MONITOR_EXIT_STATUS=1
MONITOR_INVOCATION_ID=cc8fdc149b2b4ca698d4f259f4054236
MONITOR_UNIT=myfailer.service
If mysuccess.service were to run and exit in success, then
myhandler.service would be triggered and the monitor variables
would be set as follows:
MONITOR_SERVICE_RESULT=success
MONITOR_EXIT_CODE=exited
MONITOR_EXIT_STATUS=0
MONITOR_INVOCATION_ID=6ab9af147b8c4a3ebe36e7a5f8611697
MONITOR_UNIT=mysuccess.service
systemd(1), systemctl(1), systemd-analyze(1), journalctl(1),
systemd-system.conf(5), systemd.unit(5), systemd.service(5),
systemd.socket(5), systemd.swap(5), systemd.mount(5),
systemd.kill(5), systemd.resource-control(5), systemd.time(7),
systemd.directives(7), tmpfiles.d(5), exec(3), fork(2)
1. Discoverable Partitions Specification
https://uapi-group.org/specifications/specs/discoverable_partitions_specification
2. The /proc Filesystem
https://docs.kernel.org/filesystems/proc.html#mount-options
3. User/Group Name Syntax
https://systemd.io/USER_NAMES
4. No New Privileges Flag
https://docs.kernel.org/userspace-api/no_new_privs.html
5. JSON User Record
https://systemd.io/USER_RECORD
6. The /proc Filesystem
https://docs.kernel.org/filesystems/proc.html
7. Kernel Samepage Merging
https://docs.kernel.org/admin-guide/mm/ksm.html
8. unicode scalar values
https://www.unicode.org/glossary/#unicode_scalar_value
9. unicode noncharacters
https://www.unicode.org/glossary/#noncharacter
10. unicode byte order mark
https://www.unicode.org/glossary/#byte_order_mark
11. POSIX shell unquoted text
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_02_01
12. POSIX shell single-quoted text
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_02_02
13. POSIX shell double-quoted text
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_02_03
14. Base64
https://tools.ietf.org/html/rfc2045#section-6.8
15. Container Interface
https://systemd.io/CONTAINER_INTERFACE
16. DMI/SMBIOS
https://www.dmtf.org/standards/smbios
17. qemu
https://www.qemu.org/docs/master/system/index.html
18. System and Service Credentials
https://systemd.io/CREDENTIALS
19. Memory Pressure Handling
https://systemd.io/MEMORY_PRESSURE
20. LSB specification
https://refspecs.linuxbase.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/iniscrptact.html
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have
a bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
systemd 257~devel SYSTEMD.EXEC(5)
Pages that refer to this page: homectl(1), portablectl(1), systemctl(1), systemd(1), systemd-analyze(1), systemd-ask-password(1), systemd-creds(1), systemd-cryptenroll(1), systemd-dissect(1), systemd-firstboot(1), systemd-id128(1), systemd-nspawn(1), systemd-run(1), systemd-vmspawn(1), userdbctl(1), sd_bus_creds_get_pid(3), sd_id128_get_machine(3), sd_notify(3), capsule@.service(5), journald.conf(5), org.freedesktop.portable1(5), org.freedesktop.systemd1(5), systemd.automount(5), systemd.kill(5), systemd.link(5), systemd.mount(5), systemd.netdev(5), systemd.path(5), systemd.resource-control(5), systemd.scope(5), systemd.service(5), systemd.socket(5), systemd.swap(5), systemd-system.conf(5), systemd.timer(5), systemd.unit(5), tmpfiles.d(5), user@.service(5), daemon(7), file-hierarchy(7), smbios-type-11(7), systemd.directives(7), systemd.generator(7), systemd.index(7), systemd.journal-fields(7), systemd-stub(7), systemd.v(7), nss-systemd(8), systemd-coredump(8), systemd-cryptsetup(8), systemd-journald.service(8), systemd-network-generator.service(8), systemd-nsresourced.service(8), systemd-resolved.service(8), systemd-sysctl.service(8), systemd-sysusers(8), systemd-tmpfiles(8), systemd-vconsole-setup.service(8)
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