---
name: "systemd.mstack"
section: "7"
platform: "linux"
package: "systemd"
version: "262.1-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/systemd.mstack"
---

# systemd.mstack(7)

Mount stacks in self descriptive directories

## NAME

systemd.mstack - Mount stacks in self descriptive directories

## DESCRIPTION

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)](/systemd-nspawn/1.md)'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 be 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 exists, 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)](/systemd.v/7.md) functionality may be used, for automatic selection of versioned resources.

Use the [**systemd-mstack**(1)](/systemd-mstack/1.md) tool to process or mount .mstack/ directories from the command line.

## EXAMPLES

The following .mstack/ consists of two read-only overlayfs layers as DDI, plus one writable directory 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/

## SEE ALSO

[**systemd**(1)](/systemd/1.md), [**systemd-mstack**(1)](/systemd-mstack/1.md), [**systemd-nspawn**(1)](/systemd-nspawn/1.md), [**systemd.exec**(5)](/systemd.exec/5.md), [**systemd.v**(7)](/systemd.v/7.md), [**systemd-vpick**(1)](/systemd-vpick/1.md)