Provided by: systemd-container_256.4-2ubuntu1_amd64 bug

NAME

       systemd-dissect, mount.ddi - Dissect Discoverable Disk Images (DDIs)

SYNOPSIS

       systemd-dissect [OPTIONS...] IMAGE

       systemd-dissect [OPTIONS...] [--mount] IMAGE PATH

       systemd-dissect [OPTIONS...] [--umount] PATH

       systemd-dissect [OPTIONS...] [--attach] IMAGE

       systemd-dissect [OPTIONS...] [--detach] PATH

       systemd-dissect [OPTIONS...] [--list] IMAGE

       systemd-dissect [OPTIONS...] [--mtree] IMAGE

       systemd-dissect [OPTIONS...] [--with] IMAGE [COMMAND...]

       systemd-dissect [OPTIONS...] [--copy-from] IMAGE PATH [TARGET]

       systemd-dissect [OPTIONS...] [--copy-to] IMAGE [SOURCE] PATH

       systemd-dissect [OPTIONS...] [--make-archive] IMAGE [TARGET]

       systemd-dissect [OPTIONS...] [--discover]

       systemd-dissect [OPTIONS...] [--validate] IMAGE

DESCRIPTION

       systemd-dissect is a tool for introspecting and interacting with file system OS disk
       images, specifically Discoverable Disk Images (DDIs). It supports four different
       operations:

        1. Show general OS image information, including the image's os-release(5) data, machine
           ID, partition information and more.

        2. Mount an OS image to a local directory. In this mode it will dissect the OS image and
           mount the included partitions according to their designation onto a directory and
           possibly sub-directories.

        3. Unmount an OS image from a local directory. In this mode it will recursively unmount
           the mounted partitions and remove the underlying loop device, including all the
           partition sub-devices.

        4. Copy files and directories in and out of an OS image.

       The tool may operate on three types of OS images:

        1. OS disk images containing a GPT partition table envelope, with partitions marked
           according to the Discoverable Partitions Specification[1].

        2. OS disk images containing just a plain file-system without an enveloping partition
           table. (This file system is assumed to be the root file system of the OS.)

        3. OS disk images containing a GPT or MBR partition table, with a single partition only.
           (This partition is assumed to contain the root file system of the OS.)

       OS images may use any kind of Linux-supported file systems. In addition they may make use
       of LUKS disk encryption, and contain Verity integrity information. Note that qualifying OS
       images may be booted with systemd-nspawn(1)'s --image= switch, and be used as root file
       system for system service using the RootImage= unit file setting, see systemd.exec(5).

       Note that the partition table shown when invoked without command switch (as listed below)
       does not necessarily show all partitions included in the image, but just the partitions
       that are understood and considered part of an OS disk image. Specifically, partitions of
       unknown types are ignored, as well as duplicate partitions (i.e. more than one per
       partition type), as are root and /usr/ partitions of architectures not compatible with the
       local system. In other words: this tool will display what it operates with when mounting
       the image. To display the complete list of partitions use a tool such as fdisk(8).

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

       In place of the image path a ".v/" versioned directory may be specified, see systemd.v(7)
       for details.

COMMANDS

       If neither of the command switches listed below are passed the specified disk image is
       opened and general information about the image and the contained partitions and their use
       is shown.

       --mount, -m
           Mount the specified OS image to the specified directory. This will dissect the image,
           determine the OS root file system — as well as possibly other partitions — and mount
           them to the specified directory. If the OS image contains multiple partitions marked
           with the Discoverable Partitions Specification[1] multiple nested mounts are
           established. This command expects two arguments: a path to an image file and a path to
           a directory where to mount the image.

           To unmount an OS image mounted like this use the --umount operation.

           When the OS image contains LUKS encrypted or Verity integrity protected file systems
           appropriate volumes are automatically set up and marked for automatic disassembly when
           the image is unmounted.

           The OS image may either be specified as path to an OS image stored in a regular file
           or may refer to block device node (in the latter case the block device must be the
           "whole" device, i.e. not a partition device). (The other supported commands described
           here support this, too.)

           All mounted file systems are checked with the appropriate fsck(8) implementation in
           automatic fixing mode, unless explicitly turned off (--fsck=no) or read-only operation
           is requested (--read-only).

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

           Added in version 247.

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

           Added in version 247.

       --umount, -u
           Unmount an OS image from the specified directory. This command expects one argument: a
           directory where an OS image was mounted.

           All mounted partitions will be recursively unmounted, and the underlying loop device
           will be removed, along with all its partition sub-devices.

           Added in version 252.

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

           Added in version 252.

       --attach
           Attach the specified disk image to an automatically allocated loopback block device,
           and print the path to the loopback block device to standard output. This is similar to
           an invocation of losetup --find --show, but will validate the image as DDI before
           attaching, and derive the correct sector size to use automatically. Moreover, it
           ensures the per-partition block devices are created before returning. Takes a path to
           a disk image file.

           Added in version 254.

       --detach
           Detach the specified disk image from a loopback block device. This undoes the effect
           of --attach above. This expects either a path to a loopback block device as an
           argument, or the path to the backing image file. In the latter case it will
           automatically determine the right device to detach.

           Added in version 254.

       --list, -l
           Prints the paths of all the files and directories in the specified OS image or
           directory to standard output.

           Added in version 253.

       --mtree
           Generates a BSD mtree(8) compatible file manifest of the specified disk image or
           directory. This is useful for comparing image contents in detail, including inode
           information and other metadata. While the generated manifest will contain detailed
           inode information, it currently excludes extended attributes, file system
           capabilities, MAC labels, chattr(1) file flags, btrfs(5) subvolume information, and
           various other file metadata. File content information is shown via a SHA256 digest.
           Additional fields might be added in future. Note that inode information such as link
           counts, inode numbers and timestamps is excluded from the output on purpose, as it
           typically complicates reproducibility.

           Added in version 253.

       --with
           Runs the specified command with the specified OS image mounted. This will mount the
           image to a temporary directory, switch the current working directory to it, and invoke
           the specified command line as child process. Once the process ends it will unmount the
           image again, and remove the temporary directory. If no command is specified a shell is
           invoked. The image is mounted writable, use --read-only to switch to read-only
           operation. The invoked process will have the $SYSTEMD_DISSECT_ROOT environment
           variable set, containing the absolute path name of the temporary mount point, i.e. the
           same directory that is set as the current working directory. It will also have the
           $SYSTEMD_DISSECT_DEVICE environment variable set, containing the absolute path name of
           the loop device the image was attached to.

           Added in version 253.

       --copy-from, -x
           Copies a file or directory from the specified OS image or directory into the specified
           location on the host file system. Expects three arguments: a path to an image file or
           directory, a source path (relative to the image's root directory) and a destination
           path (relative to the current working directory, or an absolute path, both outside of
           the image). If the destination path is omitted or specified as dash ("-"), the
           specified file is written to standard output. If the source path in the image file
           system refers to a regular file it is copied to the destination path. In this case
           access mode, extended attributes and timestamps are copied as well, but file ownership
           is not. If the source path in the image refers to a directory, it is copied to the
           destination path, recursively with all containing files and directories. In this case
           the file ownership is copied too.

           Added in version 247.

       --copy-to, -a
           Copies a file or directory from the specified location in the host file system into
           the specified OS image or directory. Expects three arguments: a path to an image file
           or directory, a source path (relative to the current working directory, or an absolute
           path, both outside of the image) and a destination path (relative to the image's root
           directory). If the source path is omitted or specified as dash ("-"), the data to
           write is read from standard input. If the source path in the host file system refers
           to a regular file, it is copied to the destination path. In this case access mode,
           extended attributes and timestamps are copied as well, but file ownership is not. If
           the source path in the host file system refers to a directory it is copied to the
           destination path, recursively with all containing files and directories. In this case
           the file ownership is copied too.

           As with --mount file system checks are implicitly run before the copy operation
           begins.

           Added in version 247.

       --make-archive
           Generates an archive file from the specified disk image. Expects two arguments: the
           path to the disk image and optionally the output archive file path. If the latter is
           omitted the archive is written to standard output. The archive file format is
           determined automatically from the specified output archive file name, e.g. any path
           suffixed with ".tar.xz" will result in an xz compressed UNIX tarball (if the path is
           omitted an uncompressed UNIX tarball is created). See libarchive(3) for a list of
           supported archive formats and compression schemes.

           Added in version 256.

       --discover
           Show a list of DDIs in well-known directories. This will show machine, portable
           service and system/configuration extension disk images in the usual directories
           /usr/lib/machines/, /usr/lib/portables/, /usr/lib/confexts/, /var/lib/machines/,
           /var/lib/portables/, /var/lib/extensions/ and so on.

           Added in version 253.

       --validate
           Validates the partition arrangement of a disk image (DDI), and ensures it matches the
           image policy specified via --image-policy=, if one is specified. This parses the
           partition table and probes the file systems in the image, but does not attempt to
           mount them (nor to set up disk encryption/authentication via LUKS/Verity). It does
           this taking the configured image dissection policy into account. Since this operation
           does not mount file systems, this command – unlike all other commands implemented by
           this tool – requires no privileges other than the ability to access the specified
           file. Prints "OK" and returns zero if the image appears to be in order and matches the
           specified image dissection policy. Otherwise prints an error message and returns
           non-zero.

           Added in version 254.

       -h, --help
           Print a short help text and exit.

       --version
           Print a short version string and exit.

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.

           Added in version 247.

       --fsck=no
           Turn off automatic file system checking. By default when an image is accessed for
           writing (by --mount or --copy-to) the file systems contained in the OS image are
           automatically checked using the appropriate fsck(8) command, in automatic fixing mode.
           This behavior may be switched off using --fsck=no.

           Added in version 247.

       --growfs=no
           Turn off automatic growing of accessed file systems to their partition size, if marked
           for that in the GPT partition table. By default when an image is accessed for writing
           (by --mount or --copy-to) the file systems contained in the OS image are automatically
           grown to their partition sizes, if bit 59 in the GPT partition flags is set for
           partition types that are defined by the Discoverable Partitions Specification[1]. This
           behavior may be switched off using --growfs=no. File systems are grown automatically
           on access if all of the following conditions are met:

            1. The file system is mounted writable

            2. The file system currently is smaller than the partition it is contained in (and
               thus can be grown)

            3. The image contains a GPT partition table

            4. The file system is stored on a partition defined by the Discoverable Partitions
               Specification

            5. Bit 59 of the GPT partition flags for this partition is set, as per specification

            6. The --growfs=no option is not passed.

           Added in version 249.

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

           Added in version 247.

       --rmdir
           If combined with --umount the specified directory where the OS image is mounted is
           removed after unmounting the OS image.

           Added in version 252.

       --discard=
           Takes one of "disabled", "loop", "all", "crypto". If "disabled" the image is accessed
           with empty block discarding turned off. If "loop" discarding is enabled if operating
           on a regular file. If "crypt" discarding is enabled even on encrypted file systems. If
           "all" discarding is unconditionally enabled.

           Added in version 247.

       --in-memory
           If specified an in-memory copy of the specified disk image is used. This may be used
           to operate with write-access on a (possibly read-only) image, without actually
           modifying the original file. This may also be used in order to operate on a disk image
           without keeping the originating file system busy, in order to allow it to be
           unmounted.

           Added in version 253.

       --root-hash=, --root-hash-sig=, --verity-data=
           Configure various aspects of Verity data integrity for the OS image. Option
           --root-hash= specifies a hex-encoded top-level Verity hash to use for setting up the
           Verity integrity protection. Option --root-hash-sig= specifies the path to a file
           containing a PKCS#7 signature for the hash. This signature is passed to the kernel
           during activation, which will match it against signature keys available in the kernel
           keyring. Option --verity-data= specifies a path to a file with the Verity data to use
           for the OS image, in case it is stored in a detached file. It is recommended to embed
           the Verity data directly in the image, using the Verity mechanisms in the Discoverable
           Partitions Specification[1].

           Added in version 247.

       --loop-ref=
           Configures the "reference" string the kernel shall report as backing file for the
           loopback block device. While this is supposed to be a path or filename referencing the
           backing file, this is not enforced and the kernel accepts arbitrary free-form strings,
           chosen by the user. Accepts arbitrary strings up to a length of 63 characters. This
           sets the kernel's ".lo_file_name" field for the block device. Note this is distinct
           from the /sys/class/block/loopX/loop/backing_file attribute file that always reports a
           path referring to the actual backing file. The latter is subject to mount namespace
           translation, the former is not.

           This setting is particularly useful in combination with the --attach command, as it
           allows later referencing the allocated loop device via /dev/disk/by-loop-ref/...
           symlinks. Example: first, set up the loopback device via systemd-dissect attach
           --loop-ref=quux foo.raw, and then reference it in a command via the specified
           filename: cfdisk /dev/disk/by-loop-ref/quux.

           Added in version 254.

       --mtree-hash=no
           If combined with --mtree, turns off inclusion of file hashes in the mtree output. This
           makes the --mtree faster when operating on large images.

           Added in version 254.

       --image-policy=policy
           Takes an image policy string as argument, as per systemd.image-policy(7). The policy
           is enforced when operating on the disk image specified via --image=, see above. If not
           specified defaults to the "*" policy, i.e. all recognized file systems in the image
           are used.

       --no-pager
           Do not pipe output into a pager.

       --no-legend
           Do not print the legend, i.e. column headers and the footer with hints.

       --json=MODE
           Shows output formatted as JSON. Expects one of "short" (for the shortest possible
           output without any redundant whitespace or line breaks), "pretty" (for a pretty
           version of the same, with indentation and line breaks) or "off" (to turn off JSON
           output, the default).

EXIT STATUS

       On success, 0 is returned, a non-zero failure code otherwise. If the --with command is
       used the exit status of the invoked command is propagated.

INVOCATION AS /SBIN/MOUNT.DDI

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

           # mount -t ddi myimage.raw targetdir/

       in a fashion mostly equivalent to:

           # systemd-dissect --mount myimage.raw targetdir/

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

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

           /path/to/myimage.raw /images/myimage/ ddi defaults 0 0

       When invoked this way the mount options "ro", "rw", "discard", "nodiscard" map to the
       corresponding options listed above (i.e.  --read-only, --discard=all, --discard=disabled).
       Mount options are not generically passed on to the file systems inside the images.

EXAMPLES

       Example 1. Generate a tarball from an OS disk image (--with)

           # systemd-dissect --with foo.raw tar cz . >foo.tar.gz

       or alternatively just:

       Example 2. Generate a tarball from an OS disk image (--make-archive)

           # systemd-dissect --make-archive foo.raw foo.tar.gz

SEE ALSO

       systemd(1), systemd-nspawn(1), systemd.exec(5), systemd.v(7), Discoverable Partitions
       Specification[1], mount(8), umount(8), fdisk(8)

NOTES

        1. Discoverable Partitions Specification
           https://uapi-group.org/specifications/specs/discoverable_partitions_specification