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NAME | SYNOPSIS | DESCRIPTION | COMMANDS | OPTIONS | EXIT STATUS | EXAMPLES | SEE ALSO | NOTES | COLOPHON |
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SYSTEMD-DISSECT(1) systemd-dissect SYSTEMD-DISSECT(1)
systemd-dissect - Dissect Discoverable Disk Images (DDIs)
systemd-dissect [OPTIONS...] IMAGE
systemd-dissect [OPTIONS...] --mount IMAGE PATH
systemd-dissect [OPTIONS...] --umount 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 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).
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).
-M
This is a shortcut for --mount --mkdir.
--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 it's
partition sub-devices.
-U
This is a shortcut for --umount --rmdir.
--list, -l
Prints the paths of all the files and directories in the
specified OS image to standard output.
--mtree, -l
Generates a BSD mtree(8) compatible file manifest of the
specified disk image. This is useful for comparing disk 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 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.
--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.
--copy-from, -x
Copies a file or directory from the specified OS image into
the specified location on the host file system. Expects three
arguments: a path to an image file, 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.
--copy-to, -a
Copies a file or directory from the specified location in the
host file system into the specified OS image. Expects three
arguments: a path to an image file, 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.
--discover
Show a list of DDIs in well-known directories. This will show
machine, portable service and system extension disk images in
the usual directories /usr/lib/machines/,
/usr/lib/portables/, /usr/lib/extensions/,
/var/lib/machines/, /var/lib/portables/, /var/lib/extensions/
and so on.
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
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.
--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.
--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.
--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.
--rmdir
If combined with --umount the specified directory where the
OS image is mounted is removed after unmounting the OS image.
--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.
--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.
--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].
--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).
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.
Example 1. Generate a tarball from an OS disk image
$ systemd-dissect --with foo.raw tar cz . > foo.tar.gz
systemd(1), systemd-nspawn(1), systemd.exec(5), Discoverable
Partitions Specification[1], umount(8), fdisk(8)
1. Discoverable Partitions Specification
https://uapi-group.org/specifications/specs/discoverable_partitions_specification
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 2022-12-17. (At that
time, the date of the most recent commit that was found in the
repository was 2022-12-16.) 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 252 SYSTEMD-DISSECT(1)
Pages that refer to this page: systemd.directives(7), systemd.index(7)
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