systemd-mstack

systemd

systemd-mstack

mount.mstack

Mstack Discoverable Disk Images (DDIs)

systemd-mstack

OPTIONS

IMAGE

systemd-mstack

OPTIONS

--mount

IMAGE

PATH

systemd-mstack

OPTIONS

--umount

PATH

Description

systemd-mstack is a tool for introspecting and interacting with .mstack/ mount stack directories, as described in systemd.mstack(7). It supports three different operations:

Show general mount stack information, including all described overlayfs layers and bind mounts.
Mount a mount stack to a local directory.
Unmount a mount stack from a local directory.

The systemd-mstack command may be invoked as mount.mstack in which case it implements the mount(8) "external helper" interface. This ensures mount stack directories compatible with systemd-mstack can be mounted directly by mount and fstab(5). For details see below.

Commands

If neither of the command switches listed below are passed the specified mount stack is opened and general information about it is shown, including a list of all defined layers.

--mount; -m
Mount the specified mount stack to the specified directory.

To unmount a mount stack directory mounted like this use the --umount operation.

Note that this functionality is also available in mount(8) via a command such as mount -t mstack mystack.mstack targetdir/, as well as in fstab(5). For details, see below.

-M
This is a shortcut for --mount --mkdir.

--umount; -u
Unmount a mount stack from the specified directory. This command expects one argument: a directory where mount stack was mounted.

All mounted mounts will be recursively unmounted

-U
This is a shortcut for --umount --rmdir.

Options

The following options are understood:

--read-only; -r
Operate in read-only mode. By default, --mount will establish writable mount points. If this option is specified they are established in read-only mode instead.

--mkdir
If combined with --mount the directory to mount the mount stack to is created if it is missing. Note that the directory is not automatically removed when the mount stack is unmounted again.

--rmdir
If combined with --umount the specified directory where the mount stack is mounted is removed after unmounting it.

Exit status

On success, 0 is returned, a non-zero failure code otherwise.

Invocation as `/sbin/mount.mstack`

The systemd-mstack executable may be symlinked to /sbin/mount.mstack. If invoked through that it implements mount(8)'s "external helper" interface for the (pseudo) file system type mstack. This means conformant mount stack directories may be mounted directly via

# mount -t mstack mystack.mstack targetdir/

in a fashion mostly equivalent to:

# systemd-mstack --mount mystack.mstack targetdir/

Note that since a single mount stack may contain multiple mount points it should later be unmounted with umount -R targetdir/, for recursive operation.

This functionality is particularly useful to mount mount stacks automatically at boot via simple /etc/fstab entries. For example:

/path/to/mystack.nspawn /images/mystack/ mstack defaults 0 0

When invoked this way the mount options ro, rw map to the corresponding options listed above (i.e. --read-only).