systemd.link(5) — Linux manual page

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SYSTEMD.LINK(5)               systemd.link               SYSTEMD.LINK(5)

NAME         top

       systemd.link - Network device configuration

SYNOPSIS         top

       link.link

DESCRIPTION         top

       A plain ini-style text file that encodes configuration for
       matching network devices, used by systemd-udevd(8) and in
       particular its net_setup_link builtin. See systemd.syntax(7) for
       a general description of the syntax.

       The .link files are read from the files located in the system
       network directory /usr/lib/systemd/network and
       /usr/local/lib/systemd/network, the volatile runtime network
       directory /run/systemd/network, and the local administration
       network directory /etc/systemd/network. All configuration files
       are collectively sorted and processed in alphanumeric order,
       regardless of the directories in which they live. However, files
       with identical filenames replace each other. It is recommended
       that each filename is prefixed with a number smaller than "70"
       (e.g.  10-eth0.link). Otherwise, the default .link files or those
       generated by systemd-network-generator.service(8) may take
       precedence over user configured files. Files in /etc/ have the
       highest priority, files in /run/ take precedence over files with
       the same name in /usr/lib/. This can be used to override a
       system-supplied link file with a local file if needed. As a
       special case, an empty file (file size 0) or symlink with the
       same name pointing to /dev/null disables the configuration file
       entirely (it is "masked").

       Along with the link file foo.link, a "drop-in" directory
       foo.link.d/ may exist. All files with the suffix ".conf" from
       this directory will be merged in the alphanumeric order and
       parsed after the main file itself has been parsed. This is useful
       to alter or add configuration settings, without having to modify
       the main configuration file. Each drop-in file must have
       appropriate section headers.

       In addition to /etc/systemd/network, drop-in ".d" directories can
       be placed in /usr/lib/systemd/network or /run/systemd/network
       directories. Drop-in files in /etc/ take precedence over those in
       /run/ which in turn take precedence over those in /usr/lib/.
       Drop-in files under any of these directories take precedence over
       the main link file wherever located.

       The link file contains a [Match] section, which determines if a
       given link file may be applied to a given device, as well as a
       [Link] section specifying how the device should be configured.
       The first (in lexical order) of the link files that matches a
       given device is applied. Note that a default file 99-default.link
       is shipped by the system. Any user-supplied .link should hence
       have a lexically earlier name to be considered at all.

       See udevadm(8) for diagnosing problems with .link files.

[MATCH] SECTION OPTIONS         top

       A link file is said to match an interface if all matches
       specified by the [Match] section are satisfied. When a link file
       does not contain valid settings in [Match] section, then the file
       will match all interfaces and systemd-udevd warns about that.
       Hint: to avoid the warning and to make it clear that all
       interfaces shall be matched, add the following:

           OriginalName=*

       The first (in alphanumeric order) of the link files that matches
       a given interface is applied, all later files are ignored, even
       if they match as well. The following keys are accepted:

       MACAddress=
           A whitespace-separated list of hardware addresses. The
           acceptable formats are:

           colon-delimited hexadecimal
               Each field must be one byte. E.g.  "12:34:56:78:90:ab" or
               "AA:BB:CC:DD:EE:FF".

               Added in version 250.

           hyphen-delimited hexadecimal
               Each field must be one byte. E.g.  "12-34-56-78-90-ab" or
               "AA-BB-CC-DD-EE-FF".

               Added in version 250.

           dot-delimited hexadecimal
               Each field must be two bytes. E.g.  "1234.5678.90ab" or
               "AABB.CCDD.EEFF".

               Added in version 250.

           IPv4 address format
               E.g.  "127.0.0.1" or "192.168.0.1".

               Added in version 250.

           IPv6 address format
               E.g.  "2001:0db8:85a3::8a2e:0370:7334" or "::1".

               Added in version 250.

           The total length of each MAC address must be 4 (for IPv4
           tunnel), 6 (for Ethernet), 16 (for IPv6 tunnel), or 20 (for
           InfiniBand). This option may appear more than once, in which
           case the lists are merged. If the empty string is assigned to
           this option, the list of hardware addresses defined prior to
           this is reset. Defaults to unset.

           Added in version 211.

       PermanentMACAddress=
           A whitespace-separated list of hardware's permanent
           addresses. While MACAddress= matches the device's current MAC
           address, this matches the device's permanent MAC address,
           which may be different from the current one. Use full colon-,
           hyphen- or dot-delimited hexadecimal, or IPv4 or IPv6 address
           format. This option may appear more than once, in which case
           the lists are merged. If the empty string is assigned to this
           option, the list of hardware addresses defined prior to this
           is reset. Defaults to unset.

           Added in version 245.

       Path=
           A whitespace-separated list of shell-style globs matching the
           persistent path, as exposed by the udev property ID_PATH.

           Added in version 211.

       Driver=
           A whitespace-separated list of shell-style globs matching the
           driver currently bound to the device, as exposed by the udev
           property ID_NET_DRIVER of its parent device, or if that is
           not set, the driver as exposed by ethtool -i of the device
           itself. If the list is prefixed with a "!", the test is
           inverted.

           Added in version 211.

       Type=
           A whitespace-separated list of shell-style globs matching the
           device type, as exposed by networkctl list. If the list is
           prefixed with a "!", the test is inverted. Some valid values
           are "ether", "loopback", "wlan", "wwan". Valid types are
           named either from the udev "DEVTYPE" attribute, or "ARPHRD_"
           macros in linux/if_arp.h, so this is not comprehensive.

           Added in version 211.

       Kind=
           A whitespace-separated list of shell-style globs matching the
           device kind, as exposed by networkctl status INTERFACE or ip
           -d link show INTERFACE. If the list is prefixed with a "!",
           the test is inverted. Some valid values are "bond", "bridge",
           "gre", "tun", "veth". Valid kinds are given by netlink's
           "IFLA_INFO_KIND" attribute, so this is not comprehensive.

           Added in version 251.

       Property=
           A whitespace-separated list of udev property names with their
           values after equals sign ("="). If multiple properties are
           specified, the test results are ANDed. If the list is
           prefixed with a "!", the test is inverted. If a value
           contains white spaces, then please quote whole key and value
           pair. If a value contains quotation, then please escape the
           quotation with "\".

           Example: if a .link file has the following:

               Property=ID_MODEL_ID=9999 "ID_VENDOR_FROM_DATABASE=vendor name" "KEY=with \"quotation\""

           then, the .link file matches only when an interface has all
           the above three properties.

           Added in version 243.

       OriginalName=
           A whitespace-separated list of shell-style globs matching the
           device name, as exposed by the udev property "INTERFACE".
           This cannot be used to match on names that have already been
           changed from userspace. Caution is advised when matching on
           kernel-assigned names, as they are known to be unstable
           between reboots.

           Added in version 218.

       Host=
           Matches against the hostname or machine ID of the host. See
           ConditionHost= in systemd.unit(5) for details. When prefixed
           with an exclamation mark ("!"), the result is negated. If an
           empty string is assigned, the previously assigned value is
           cleared.

           Added in version 211.

       Virtualization=
           Checks whether the system is executed in a virtualized
           environment and optionally test whether it is a specific
           implementation. See ConditionVirtualization= in
           systemd.unit(5) for details. When prefixed with an
           exclamation mark ("!"), the result is negated. If an empty
           string is assigned, the previously assigned value is cleared.

           Added in version 211.

       KernelCommandLine=
           Checks whether a specific kernel command line option is set.
           See ConditionKernelCommandLine= in systemd.unit(5) for
           details. When prefixed with an exclamation mark ("!"), the
           result is negated. If an empty string is assigned, the
           previously assigned value is cleared.

           Added in version 211.

       KernelVersion=
           Checks whether the kernel version (as reported by uname -r)
           matches a certain expression. See ConditionKernelVersion= in
           systemd.unit(5) for details. When prefixed with an
           exclamation mark ("!"), the result is negated. If an empty
           string is assigned, the previously assigned value is cleared.

           Added in version 237.

       Credential=
           Checks whether the specified credential was passed to the
           systemd-udevd.service service. See System and Service
           Credentials[1] for details. When prefixed with an exclamation
           mark ("!"), the result is negated. If an empty string is
           assigned, the previously assigned value is cleared.

           Added in version 252.

       Architecture=
           Checks whether the system is running on a specific
           architecture. See ConditionArchitecture= in systemd.unit(5)
           for details. When prefixed with an exclamation mark ("!"),
           the result is negated. If an empty string is assigned, the
           previously assigned value is cleared.

           Added in version 211.

       Firmware=
           Checks whether the system is running on a machine with the
           specified firmware. See ConditionFirmware= in systemd.unit(5)
           for details. When prefixed with an exclamation mark ("!"),
           the result is negated. If an empty string is assigned, the
           previously assigned value is cleared.

           Added in version 249.

[LINK] SECTION OPTIONS         top

       The [Link] section accepts the following keys:

       Description=
           A description of the device.

           Added in version 211.

       Alias=
           The ifalias interface property is set to this value.

           Added in version 211.

       MACAddressPolicy=
           The policy by which the MAC address should be set. The
           available policies are:

           persistent
               If the hardware has a persistent MAC address, as most
               hardware should, and if it is used by the kernel, nothing
               is done. Otherwise, a new MAC address is generated which
               is guaranteed to be the same on every boot for the given
               machine and the given device, but which is otherwise
               random. This feature depends on ID_NET_NAME_* properties
               to exist for the link. On hardware where these properties
               are not set, the generation of a persistent MAC address
               will fail.

               Added in version 211.

           random
               If the kernel is using a random MAC address, nothing is
               done. Otherwise, a new address is randomly generated each
               time the device appears, typically at boot. Either way,
               the random address will have the "unicast" and "locally
               administered" bits set.

               Added in version 211.

           none
               Keeps the MAC address assigned by the kernel. Or use the
               MAC address specified in MACAddress=.

               Added in version 227.

           An empty string assignment is equivalent to setting "none".

           Added in version 211.

       MACAddress=
           The interface MAC address to use. For this setting to take
           effect, MACAddressPolicy= must either be unset, empty, or
           "none".

           Added in version 211.

       NamePolicy=
           An ordered, space-separated list of policies by which the
           interface name should be set.  NamePolicy= may be disabled by
           specifying net.ifnames=0 on the kernel command line. Each of
           the policies may fail, and the first successful one is used.
           The name is not set directly, but is exported to udev as the
           property ID_NET_NAME, which is, by default, used by a
           udev(7), rule to set NAME. The available policies are:

           kernel
               If the kernel claims that the name it has set for a
               device is predictable, then no renaming is performed.

               Added in version 216.

           database
               The name is set based on entries in the udev's Hardware
               Database with the key ID_NET_NAME_FROM_DATABASE.

               Added in version 211.

           onboard
               The name is set based on information given by the
               firmware for on-board devices, as exported by the udev
               property ID_NET_NAME_ONBOARD. See
               systemd.net-naming-scheme(7).

               Added in version 211.

           slot
               The name is set based on information given by the
               firmware for hot-plug devices, as exported by the udev
               property ID_NET_NAME_SLOT. See
               systemd.net-naming-scheme(7).

               Added in version 211.

           path
               The name is set based on the device's physical location,
               as exported by the udev property ID_NET_NAME_PATH. See
               systemd.net-naming-scheme(7).

               Added in version 211.

           mac
               The name is set based on the device's persistent MAC
               address, as exported by the udev property
               ID_NET_NAME_MAC. See systemd.net-naming-scheme(7).

               Added in version 211.

           keep
               If the device already had a name given by userspace (as
               part of creation of the device or a rename), keep it.

               Added in version 241.

           Added in version 211.

       Name=
           The interface name to use. This option has lower precedence
           than NamePolicy=, so for this setting to take effect,
           NamePolicy= must either be unset, empty, disabled, or all
           policies configured there must fail. Also see the example
           below with "Name=dmz0".

           Note that specifying a name that the kernel might use for
           another interface (for example "eth0") is dangerous because
           the name assignment done by udev will race with the
           assignment done by the kernel, and only one interface may use
           the name. Depending on the order of operations, either udev
           or the kernel will win, making the naming unpredictable. It
           is best to use some different prefix, for example
           "internal0"/"external0" or "lan0"/"lan1"/"lan3".

           Interface names must have a minimum length of 1 character and
           a maximum length of 15 characters, and may contain any 7bit
           ASCII character, with the exception of control characters,
           ":", "/" and "%". While "."  is an allowed character, it's
           recommended to avoid it when naming interfaces as various
           tools (such as resolvconf(1)) use it as separator character.
           Also, fully numeric interface names are not allowed (in order
           to avoid ambiguity with interface specification by numeric
           indexes), as are the special strings ".", "..", "all" and
           "default".

           Added in version 211.

       AlternativeNamesPolicy=
           A space-separated list of policies by which the interface's
           alternative names should be set. Each of the policies may
           fail, and all successful policies are used. The available
           policies are "database", "onboard", "slot", "path", and
           "mac". If the kernel does not support the alternative names,
           then this setting will be ignored.

           Added in version 245.

       AlternativeName=
           The alternative interface name to use. This option can be
           specified multiple times. If the empty string is assigned to
           this option, the list is reset, and all prior assignments
           have no effect. If the kernel does not support the
           alternative names, then this setting will be ignored.

           Alternative interface names may be used to identify
           interfaces in various tools. In contrast to the primary name
           (as configured with Name= above) there may be multiple
           alternative names referring to the same interface.
           Alternative names may have a maximum length of 127
           characters, in contrast to the 15 allowed for the primary
           interface name, but otherwise are subject to the same naming
           constraints.

           Added in version 245.

       TransmitQueues=
           Specifies the device's number of transmit queues. An integer
           in the range 1...4096. When unset, the kernel's default will
           be used.

           Added in version 248.

       ReceiveQueues=
           Specifies the device's number of receive queues. An integer
           in the range 1...4096. When unset, the kernel's default will
           be used.

           Added in version 248.

       TransmitQueueLength=
           Specifies the transmit queue length of the device in number
           of packets. An unsigned integer in the range 0...4294967294.
           When unset, the kernel's default will be used.

           Added in version 248.

       MTUBytes=
           The maximum transmission unit in bytes to set for the device.
           The usual suffixes K, M, G are supported and are understood
           to the base of 1024.

           Added in version 211.

       BitsPerSecond=
           The speed to set for the device, the value is rounded down to
           the nearest Mbps. The usual suffixes K, M, G are supported
           and are understood to the base of 1000.

           Added in version 211.

       Duplex=
           The duplex mode to set for the device. The accepted values
           are half and full.

           Added in version 211.

       AutoNegotiation=
           Takes a boolean. If set to yes, automatic negotiation of
           transmission parameters is enabled. Autonegotiation is a
           procedure by which two connected ethernet devices choose
           common transmission parameters, such as speed, duplex mode,
           and flow control. When unset, the kernel's default will be
           used.

           Note that if autonegotiation is enabled, speed and duplex
           settings are read-only. If autonegotiation is disabled, speed
           and duplex settings are writable if the driver supports
           multiple link modes.

           Added in version 233.

       WakeOnLan=
           The Wake-on-LAN policy to set for the device. Takes the
           special value "off" which disables Wake-on-LAN, or space
           separated list of the following words:

           phy
               Wake on PHY activity.

               Added in version 211.

           unicast
               Wake on unicast messages.

               Added in version 235.

           multicast
               Wake on multicast messages.

               Added in version 235.

           broadcast
               Wake on broadcast messages.

               Added in version 235.

           arp
               Wake on ARP.

               Added in version 235.

           magic
               Wake on receipt of a magic packet.

               Added in version 211.

           secureon
               Enable SecureOn password for MagicPacket. Implied when
               WakeOnLanPassword= is specified. If specified without
               WakeOnLanPassword= option, then the password is read from
               the credential "LINK.link.wol.password" (e.g.,
               "60-foo.link.wol.password"), and if the credential not
               found, then read from "wol.password". See
               ImportCredential=/LoadCredential=/SetCredential= in
               systemd.exec(1) for details. The password in the
               credential, must be 6 bytes in hex format with each byte
               separated by a colon (":") like an Ethernet MAC address,
               e.g., "aa:bb:cc:dd:ee:ff".

               Added in version 235.

           Defaults to unset, and the device's default will be used.
           This setting can be specified multiple times. If an empty
           string is assigned, then the all previous assignments are
           cleared.

           Added in version 211.

       WakeOnLanPassword=
           Specifies the SecureOn password for MagicPacket. Takes an
           absolute path to a regular file or an AF_UNIX stream socket,
           or the plain password. When a path to a regular file is
           specified, the password is read from it. When an AF_UNIX
           stream socket is specified, a connection is made to it and
           the password is read from it. The password must be 6 bytes in
           hex format with each byte separated by a colon (":") like an
           Ethernet MAC address, e.g., "aa:bb:cc:dd:ee:ff". This implies
           WakeOnLan=secureon. Defaults to unset, and the current value
           will not be changed.

           Added in version 250.

       Port=
           The port option is used to select the device port. The
           supported values are:

           tp
               An Ethernet interface using Twisted-Pair cable as the
               medium.

               Added in version 234.

           aui
               Attachment Unit Interface (AUI). Normally used with hubs.

               Added in version 234.

           bnc
               An Ethernet interface using BNC connectors and co-axial
               cable.

               Added in version 234.

           mii
               An Ethernet interface using a Media Independent Interface
               (MII).

               Added in version 234.

           fibre
               An Ethernet interface using Optical Fibre as the medium.

               Added in version 234.

           Added in version 234.

       Advertise=
           This sets what speeds and duplex modes of operation are
           advertised for auto-negotiation. This implies
           "AutoNegotiation=yes". The supported values are:

           Table 1. Supported advertise values
           ┌────────────────────────────┬──────────────┬─────────────┐
           │ Advertise                  Speed (Mbps) Duplex Mode │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 10baset-full               │ 10           │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 10baset1l-full             │ 10           │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 10baset-half               │ 10           │ half        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100basefx-full             │ 100          │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100baset-full              │ 100          │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100baset1-full             │ 100          │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100basefx-half             │ 100          │ half        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100baset-half              │ 100          │ half        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 1000basekx-full            │ 1000         │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 1000baset-full             │ 1000         │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 1000baset1-full            │ 1000         │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 1000basex-full             │ 1000         │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 1000baset-half             │ 1000         │ half        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 2500baset-full             │ 2500         │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 2500basex-full             │ 2500         │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 5000baset-full             │ 5000         │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 10000baser-fec             │ 10000        │             │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 10000basecr-full           │ 10000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 10000baseer-full           │ 10000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 10000basekr-full           │ 10000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 10000basekx4-full          │ 10000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 10000baselr-full           │ 10000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 10000baselrm-full          │ 10000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 10000basesr-full           │ 10000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 10000baset-full            │ 10000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 20000basekr2-full          │ 20000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 20000basemld2-full         │ 20000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 25000basecr-full           │ 25000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 25000basekr-full           │ 25000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 25000basesr-full           │ 25000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 40000basecr4-full          │ 40000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 40000basekr4-full          │ 40000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 40000baselr4-full          │ 40000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 40000basesr4-full          │ 40000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 50000basecr-full           │ 50000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 50000basecr2-full          │ 50000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 50000basedr-full           │ 50000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 50000basekr-full           │ 50000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 50000basekr2-full          │ 50000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 50000baselr-er-fr-full     │ 50000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 50000basesr-full           │ 50000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 50000basesr2-full          │ 50000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 56000basecr4-full          │ 56000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 56000basekr4-full          │ 56000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 56000baselr4-full          │ 56000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 56000basesr4-full          │ 56000        │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000basecr-full          │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000basecr2-full         │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000basecr4-full         │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000basedr-full          │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000basedr2-full         │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000basekr-full          │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000basekr2-full         │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000basekr4-full         │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000baselr-er-fr-full    │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000baselr2-er2-fr2-full │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000baselr4-er4-full     │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000basesr-full          │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000basesr2-full         │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 100000basesr4-full         │ 100000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 200000basecr2-full         │ 200000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 200000basecr4-full         │ 200000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 200000basedr2-full         │ 200000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 200000basedr4-full         │ 200000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 200000basekr2-full         │ 200000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 200000basekr4-full         │ 200000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 200000baselr2-er2-fr2-full │ 200000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 200000baselr4-er4-fr4-full │ 200000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 200000basesr2-full         │ 200000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 200000basesr4-full         │ 200000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 400000basecr4-full         │ 400000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 400000basecr8-full         │ 400000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 400000basedr4-full         │ 400000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 400000basedr8-full         │ 400000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 400000basekr4-full         │ 400000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 400000basekr8-full         │ 400000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 400000baselr4-er4-fr4-full │ 400000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 400000baselr8-er8-fr8-full │ 400000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 400000basesr4-full         │ 400000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 400000basesr8-full         │ 400000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 800000basecr8-full         │ 800000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 800000basedr8-2-full       │ 800000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 800000basedr8-full         │ 800000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 800000basekr8-full         │ 800000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 800000basesr8-full         │ 800000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ 800000basevr8-full         │ 800000       │ full        │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ asym-pause                 │              │             │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ aui                        │              │             │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ autonegotiation            │              │             │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ backplane                  │              │             │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ bnc                        │              │             │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ fec-baser                  │              │             │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ fec-llrs                   │              │             │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ fec-none                   │              │             │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ fec-rs                     │              │             │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ fibre                      │              │             │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ mii                        │              │             │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ pause                      │              │             │
           ├────────────────────────────┼──────────────┼─────────────┤
           │ tp                         │              │             │
           └────────────────────────────┴──────────────┴─────────────┘

           By default this is unset, i.e. all possible modes will be
           advertised. This option may be specified more than once, in
           which case all specified speeds and modes are advertised. If
           the empty string is assigned to this option, the list is
           reset, and all prior assignments have no effect.

           Added in version 240.

       ReceiveChecksumOffload=
           Takes a boolean. If set to true, hardware offload for
           checksumming of ingress network packets is enabled. When
           unset, the kernel's default will be used.

           Added in version 245.

       TransmitChecksumOffload=
           Takes a boolean. If set to true, hardware offload for
           checksumming of egress network packets is enabled. When
           unset, the kernel's default will be used.

           Added in version 245.

       TCPSegmentationOffload=
           Takes a boolean. If set to true, TCP Segmentation Offload
           (TSO) is enabled. When unset, the kernel's default will be
           used.

           Added in version 232.

       TCP6SegmentationOffload=
           Takes a boolean. If set to true, TCP6 Segmentation Offload
           (tx-tcp6-segmentation) is enabled. When unset, the kernel's
           default will be used.

           Added in version 235.

       GenericSegmentationOffload=
           Takes a boolean. If set to true, Generic Segmentation Offload
           (GSO) is enabled. When unset, the kernel's default will be
           used.

           Added in version 232.

       GenericReceiveOffload=
           Takes a boolean. If set to true, Generic Receive Offload
           (GRO) is enabled. When unset, the kernel's default will be
           used.

           Added in version 232.

       GenericReceiveOffloadHardware=
           Takes a boolean. If set to true, hardware accelerated Generic
           Receive Offload (GRO) is enabled. When unset, the kernel's
           default will be used.

           Added in version 250.

       LargeReceiveOffload=
           Takes a boolean. If set to true, Large Receive Offload (LRO)
           is enabled. When unset, the kernel's default will be used.

           Added in version 232.

       ReceiveVLANCTAGHardwareAcceleration=
           Takes a boolean. If set to true, receive VLAN CTAG hardware
           acceleration is enabled. When unset, the kernel's default
           will be used.

           Added in version 250.

       TransmitVLANCTAGHardwareAcceleration=
           Takes a boolean. If set to true, transmit VLAN CTAG hardware
           acceleration is enabled. When unset, the kernel's default
           will be used.

           Added in version 250.

       ReceiveVLANCTAGFilter=
           Takes a boolean. If set to true, receive filtering on VLAN
           CTAGs is enabled. When unset, the kernel's default will be
           used.

           Added in version 250.

       TransmitVLANSTAGHardwareAcceleration=
           Takes a boolean. If set to true, transmit VLAN STAG hardware
           acceleration is enabled. When unset, the kernel's default
           will be used.

           Added in version 250.

       NTupleFilter=
           Takes a boolean. If set to true, receive N-tuple filters and
           actions are enabled. When unset, the kernel's default will be
           used.

           Added in version 250.

       RxChannels=, TxChannels=, OtherChannels=, CombinedChannels=
           Specifies the number of receive, transmit, other, or combined
           channels, respectively. Takes an unsigned integer in the
           range 1...4294967295 or "max". If set to "max", the
           advertised maximum value of the hardware will be used. When
           unset, the number will not be changed. Defaults to unset.

           Added in version 239.

       RxBufferSize=, RxMiniBufferSize=, RxJumboBufferSize=,
       TxBufferSize=
           Specifies the maximum number of pending packets in the NIC
           receive buffer, mini receive buffer, jumbo receive buffer, or
           transmit buffer, respectively. Takes an unsigned integer in
           the range 1...4294967295 or "max". If set to "max", the
           advertised maximum value of the hardware will be used. When
           unset, the number will not be changed. Defaults to unset.

           Added in version 244.

       RxFlowControl=
           Takes a boolean. When set, enables receive flow control, also
           known as the ethernet receive PAUSE message (generate and
           send ethernet PAUSE frames). When unset, the kernel's default
           will be used.

           Added in version 246.

       TxFlowControl=
           Takes a boolean. When set, enables transmit flow control,
           also known as the ethernet transmit PAUSE message (respond to
           received ethernet PAUSE frames). When unset, the kernel's
           default will be used.

           Added in version 246.

       AutoNegotiationFlowControl=
           Takes a boolean. When set, auto negotiation enables the
           interface to exchange state advertisements with the connected
           peer so that the two devices can agree on the ethernet PAUSE
           configuration. When unset, the kernel's default will be used.

           Added in version 246.

       GenericSegmentOffloadMaxBytes=
           Specifies the maximum size of a Generic Segment Offload (GSO)
           packet the device should accept. The usual suffixes K, M, G
           are supported and are understood to the base of 1024. An
           unsigned integer in the range 1...65536. Defaults to unset.

           Added in version 248.

       GenericSegmentOffloadMaxSegments=
           Specifies the maximum number of Generic Segment Offload (GSO)
           segments the device should accept. An unsigned integer in the
           range 1...65535. Defaults to unset.

           Added in version 248.

       UseAdaptiveRxCoalesce=, UseAdaptiveTxCoalesce=
           Boolean properties that, when set, enable/disable adaptive
           Rx/Tx coalescing if the hardware supports it. When unset, the
           kernel's default will be used.

           Added in version 250.

       RxCoalesceSec=, RxCoalesceIrqSec=, RxCoalesceLowSec=,
       RxCoalesceHighSec=, TxCoalesceSec=, TxCoalesceIrqSec=,
       TxCoalesceLowSec=, TxCoalesceHighSec=
           These properties configure the delay before Rx/Tx interrupts
           are generated after a packet is sent/received. The "Irq"
           properties come into effect when the host is servicing an
           IRQ. The "Low" and "High" properties come into effect when
           the packet rate drops below the low packet rate threshold or
           exceeds the high packet rate threshold respectively if
           adaptive Rx/Tx coalescing is enabled. When unset, the
           kernel's defaults will be used.

           Added in version 250.

       RxMaxCoalescedFrames=, RxMaxCoalescedIrqFrames=,
       RxMaxCoalescedLowFrames=, RxMaxCoalescedHighFrames=,
       TxMaxCoalescedFrames=, TxMaxCoalescedIrqFrames=,
       TxMaxCoalescedLowFrames=, TxMaxCoalescedHighFrames=
           These properties configure the maximum number of frames that
           are sent/received before a Rx/Tx interrupt is generated. The
           "Irq" properties come into effect when the host is servicing
           an IRQ. The "Low" and "High" properties come into effect when
           the packet rate drops below the low packet rate threshold or
           exceeds the high packet rate threshold respectively if
           adaptive Rx/Tx coalescing is enabled. When unset, the
           kernel's defaults will be used.

           Added in version 250.

       CoalescePacketRateLow=, CoalescePacketRateHigh=
           These properties configure the low and high packet rate
           (expressed in packets per second) threshold respectively and
           are used to determine when the corresponding coalescing
           settings for low and high packet rates come into effect if
           adaptive Rx/Tx coalescing is enabled. If unset, the kernel's
           defaults will be used.

           Added in version 250.

       CoalescePacketRateSampleIntervalSec=
           Configures how often to sample the packet rate used for
           adaptive Rx/Tx coalescing. This property cannot be zero. This
           lowest time granularity supported by this property is
           seconds. Partial seconds will be rounded up before being
           passed to the kernel. If unset, the kernel's default will be
           used.

           Added in version 250.

       StatisticsBlockCoalesceSec=
           How long to delay driver in-memory statistics block updates.
           If the driver does not have an in-memory statistic block,
           this property is ignored. This property cannot be zero. If
           unset, the kernel's default will be used.

           Added in version 250.

       MDI=
           Specifies the medium dependent interface (MDI) mode for the
           interface. A MDI describes the interface from a physical
           layer implementation to the physical medium used to carry the
           transmission. Takes one of the following words: "straight"
           (or equivalently: "mdi"), "crossover" (or equivalently:
           "mdi-x", "mdix"), and "auto". When "straight", the MDI
           straight through mode will be used. When "crossover", the MDI
           crossover (MDI-X) mode will be used. When "auto", the MDI
           status is automatically detected. Defaults to unset, and the
           kernel's default will be used.

           Added in version 251.

       SR-IOVVirtualFunctions=
           Specifies the number of SR-IOV virtual functions. Takes an
           integer in the range 0...2147483647. Defaults to unset, and
           automatically determined from the values specified in the
           VirtualFunction= settings in the [SR-IOV] sections.

           Added in version 251.

[SR-IOV] SECTION OPTIONS         top

       The [SR-IOV] section accepts the following keys. Specify several
       [SR-IOV] sections to configure several SR-IOVs. SR-IOV provides
       the ability to partition a single physical PCI resource into
       virtual PCI functions which can then be injected into a VM. In
       the case of network VFs, SR-IOV improves north-south network
       performance (that is, traffic with endpoints outside the host
       machine) by allowing traffic to bypass the host machine’s network
       stack.

       VirtualFunction=
           Specifies a Virtual Function (VF), lightweight PCIe function
           designed solely to move data in and out. Takes an integer in
           the range 0...2147483646. This option is compulsory.

           Added in version 251.

       VLANId=
           Specifies VLAN ID of the virtual function. Takes an integer
           in the range 1...4095.

           Added in version 251.

       QualityOfService=
           Specifies quality of service of the virtual function. Takes
           an integer in the range 1...4294967294.

           Added in version 251.

       VLANProtocol=
           Specifies VLAN protocol of the virtual function. Takes
           "802.1Q" or "802.1ad".

           Added in version 251.

       MACSpoofCheck=
           Takes a boolean. Controls the MAC spoof checking. When unset,
           the kernel's default will be used.

           Added in version 251.

       QueryReceiveSideScaling=
           Takes a boolean. Toggle the ability of querying the receive
           side scaling (RSS) configuration of the virtual function
           (VF). The VF RSS information like RSS hash key may be
           considered sensitive on some devices where this information
           is shared between VF and the physical function (PF). When
           unset, the kernel's default will be used.

           Added in version 251.

       Trust=
           Takes a boolean. Allows one to set trust mode of the virtual
           function (VF). When set, VF users can set a specific feature
           which may impact security and/or performance. When unset, the
           kernel's default will be used.

           Added in version 251.

       LinkState=
           Allows one to set the link state of the virtual function
           (VF). Takes a boolean or a special value "auto". Setting to
           "auto" means a reflection of the physical function (PF) link
           state, "yes" lets the VF to communicate with other VFs on
           this host even if the PF link state is down, "no" causes the
           hardware to drop any packets sent by the VF. When unset, the
           kernel's default will be used.

           Added in version 251.

       MACAddress=
           Specifies the MAC address for the virtual function.

           Added in version 251.

EXAMPLES         top

       Example 1. /usr/lib/systemd/network/99-default.link

       The link file 99-default.link that is shipped with systemd
       defines the default policies for the interface name, alternative
       names, and MAC address of links.

           [Match]
           OriginalName=*

           [Link]
           NamePolicy=keep kernel database onboard slot path
           AlternativeNamesPolicy=database onboard slot path
           MACAddressPolicy=persistent

       Example 2. /etc/systemd/network/10-dmz.link

       This example assigns the fixed name "dmz0" to the interface with
       the MAC address 00:a0:de:63:7a:e6:

           [Match]
           MACAddress=00:a0:de:63:7a:e6

           [Link]
           Name=dmz0

       NamePolicy= is not set, so Name= takes effect. We use the "10-"
       prefix to order this file early in the list. Note that it needs
       to be before 99-default.link, i.e. it needs a numerical prefix,
       to have any effect at all.

       Example 3. (Re-)applying a .link file to an interface

       After a new .link file has been created, or an existing .link
       file modified, the new settings may be applied to the matching
       interface with the following commands:

           $ sudo udevadm control --reload
           $ sudo ip link set eth0 down
           $ sudo udevadm trigger --verbose --settle --action add /sys/class/net/eth0

       You may also need to stop the service that manages the network
       interface, e.g.  systemd-networkd.service(8) or
       NetworkManager.service before the above operation, and then
       restart the service after that. For more details about udevadm
       command, see udevadm(8).

       Example 4. Debugging NamePolicy= assignments

           $ sudo SYSTEMD_LOG_LEVEL=debug udevadm test-builtin net_setup_link /sys/class/net/hub0
           ...
           Parsed configuration file /usr/lib/systemd/network/99-default.link
           Parsed configuration file /etc/systemd/network/10-eth0.link
           ID_NET_DRIVER=cdc_ether
           Config file /etc/systemd/network/10-eth0.link applies to device hub0
           link_config: autonegotiation is unset or enabled, the speed and duplex are not writable.
           hub0: Device has name_assign_type=4
           Using default interface naming scheme 'v240'.
           hub0: Policies didn't yield a name, using specified Name=hub0.
           ID_NET_LINK_FILE=/etc/systemd/network/10-eth0.link
           ID_NET_NAME=hub0
           ...

       Explicit Name= configuration wins in this case.

           sudo SYSTEMD_LOG_LEVEL=debug udevadm test-builtin net_setup_link /sys/class/net/enp0s31f6
           ...
           Parsed configuration file /usr/lib/systemd/network/99-default.link
           Parsed configuration file /etc/systemd/network/10-eth0.link
           Created link configuration context.
           ID_NET_DRIVER=e1000e
           Config file /usr/lib/systemd/network/99-default.link applies to device enp0s31f6
           link_config: autonegotiation is unset or enabled, the speed and duplex are not writable.
           enp0s31f6: Device has name_assign_type=4
           Using default interface naming scheme 'v240'.
           enp0s31f6: Policy *keep*: keeping existing userspace name
           enp0s31f6: Device has addr_assign_type=0
           enp0s31f6: MAC on the device already matches policy *persistent*
           ID_NET_LINK_FILE=/usr/lib/systemd/network/99-default.link
           ...

       In this case, the interface was already renamed, so the keep
       policy specified as the first option in 99-default.link means
       that the existing name is preserved. If keep was removed, or if
       were in boot before the renaming has happened, we might get the
       following instead:

           enp0s31f6: Policy *path* yields "enp0s31f6".
           enp0s31f6: Device has addr_assign_type=0
           enp0s31f6: MAC on the device already matches policy *persistent*
           ID_NET_LINK_FILE=/usr/lib/systemd/network/99-default.link
           ID_NET_NAME=enp0s31f6
           ...

       Please note that the details of output are subject to change.

       Example 5. /etc/systemd/network/10-internet.link

       This example assigns the fixed name "internet0" to the interface
       with the device path "pci-0000:00:1a.0-*":

           [Match]
           Path=pci-0000:00:1a.0-*

           [Link]
           Name=internet0

       Example 6. /etc/systemd/network/25-wireless.link

       Here's an overly complex example that shows the use of a large
       number of [Match] and [Link] settings.

           [Match]
           MACAddress=12:34:56:78:9a:bc
           Driver=brcmsmac
           Path=pci-0000:02:00.0-*
           Type=wlan
           Virtualization=no
           Host=my-laptop
           Architecture=x86-64

           [Link]
           Name=wireless0
           MTUBytes=1450
           BitsPerSecond=10M
           WakeOnLan=magic
           MACAddress=cb:a9:87:65:43:21

SEE ALSO         top

       systemd-udevd.service(8), udevadm(8), systemd.netdev(5),
       systemd.network(5), systemd-network-generator.service(8)

NOTES         top

        1. System and Service Credentials
           https://systemd.io/CREDENTIALS

COLOPHON         top

       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 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-22.)  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 255                                              SYSTEMD.LINK(5)

Pages that refer to this page: networkctl(1)systemd.netdev(5)systemd.network(5)systemd.directives(7)systemd.index(7)systemd.net-naming-scheme(7)systemd.syntax(7)udev(7)systemd-networkd.service(8)systemd-network-generator.service(8)systemd-udevd.service(8)