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NAME | DESCRIPTION | EXAMPLES | SEE ALSO | COLOPHON |
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SYSTEMD.MSTACK(7) systemd.mstack SYSTEMD.MSTACK(7)
systemd.mstack - Mount stacks in self descriptive directories
Directories with the ".mstack/" suffix may encode 'mount stacks'
for assembling OS mount hierarchies based on bind and overlay
mounts, for use in systemd-nspawn(1)'s --mstack= switch or the
service manager's RootMStack= setting for services. ".mstack/"
directories may contain various files and subdirectories, where
each will effect one layer of an "overlayfs" mount, or a bind
mount. The name of the file or subdirectory indicates how it shall
used in the mount hierarchy. Specifically, the following names are
defined:
1. A layer@id/ directory will be turned into a layer of an
overlayfs mount. The "id" identifier is used to define the
order of the layers: a version sort is executed, with the
first entry being the bottom layer in the "overlayfs" stack,
and the last entry becoming the highest layer (precisely:
highest "lowerdir") in the "overlayfs" stack.
2. Similar, a layer@id.raw regular file will be mounted as a DDI,
and the resulting mount will be turned into an overlayfs
layer, following the same sorting rules.
3. An rw directory will be turned into a writable layer at the
very top of the "overlayfs" stack. A subdirectory data of it
will become the "upperdir", a subdirectory work will become
the "workdir". Note that these two subdirectories do not need
to be created explicitly, they are created automatically on
first use should they be missing.
4. A bind@location/ directory will be bind mounted to the mount
point indicated by the location identifier, in read-write
fashion. The location is encoded via the same escaping logic
used for naming ".mount" units, i.e. slashes become dashes.
5. Similar, a bind@location.raw file will be mounted as a DDI,
and the resulting mount bind mounted to the specified
location.
6. A robind@location/ is treated very similar to bind@location/,
but the resulting bind mount is read-only.
7. Similar, robind@location.raw creates a read-only bind mount
from a DDI.
8. If a root/ subdirectory it is used as root of the resulting
mount hierarchy, and only the usr/ subtree of the overlayfs
mount will be bound to usr/ in the hierarchy.
Note that each of the entry types above may be a symbolic link
pointing to a directory or image file, instead a directory or
image file itself.
On each listed file or subdirectory type the systemd.v(7)
functionality may be used, for automatic selection of versioned
resources.
Use the systemd-mstack(1) tool to process or mount .mstack/
directories from the command line.
The following .mstack/ consists of two read-only overlayfs layers
as DDI, plus one writable directory one on top. The read-only
layers are symlinked:
1. foobar.mstack/layer@0.raw → ../base.raw
2. foobar.mstack/layer@1.raw → ../app.raw
3. foobar.mstack/rw/
The following .mstack/ consists of a read-only DDI mounted to
"/usr/" and writable root:
1. waldo.mstack/layer@0.raw → ../vendor.raw
2. waldo.mstack/root/
The following .mstack/ consists of a read-only DDI mounted as
root, but a writable /var/ mounted on top:
1. quux.mstack/layer@0.raw → ../myapp1.raw
2. quux.mstack/bind:var → ../myapp1-var/
systemd(1), systemd-mstack(1), systemd-nspawn(1), systemd.exec(5),
systemd.v(7), systemd-vpick(1)
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 2026-05-24. (At that
time, the date of the most recent commit that was found in the
repository was 2026-05-24.) 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 261~rc1 SYSTEMD.MSTACK(7)
Pages that refer to this page: systemd-mstack(1), systemd-nspawn(1), org.freedesktop.import1(5), systemd.exec(5), systemd.directives(7), systemd.index(7)
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HTML rendering created 2026-05-25 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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