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man: document systemd-dissect

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man/rules/meson.build
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@ -818,6 +818,7 @@ manpages = [
['systemd-debug-generator', '8', [], ''],
['systemd-delta', '1', [], ''],
['systemd-detect-virt', '1', [], ''],
['systemd-dissect', '1', [], ''],
['systemd-environment-d-generator',
'8',
['30-systemd-environment-d-generator'],

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man/systemd-dissect.xml Normal file
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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<refentry id="systemd-dissect"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>systemd-dissect</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>systemd-dissect</refentrytitle>
<manvolnum>1</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd-dissect</refname>
<refpurpose>Dissect file system OS images</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg></command>
</cmdsynopsis>
<cmdsynopsis>
<command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--mount</option> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="plain"><replaceable>PATH</replaceable></arg></command>
</cmdsynopsis>
<cmdsynopsis>
<command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--copy-from</option> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="plain"><replaceable>PATH</replaceable></arg> <arg choice="opt"><replaceable>TARGET</replaceable></arg></command>
</cmdsynopsis>
<cmdsynopsis>
<command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--copy-to</option> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="opt"><replaceable>SOURCE</replaceable></arg> <arg choice="plain"><replaceable>PATH</replaceable></arg></command>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><command>systemd-dissect</command> is a tool for introspecting and interacting with file system OS
disk images. It supports four different operations:</para>
<orderedlist>
<listitem><para>Show general OS image information, including the image's
<citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry> data,
machine ID, partition information and more.</para></listitem>
<listitem><para>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.</para></listitem>
<listitem><para>Copy files and directories in and out of an OS image.</para></listitem>
</orderedlist>
<para>The tool may operate on three types of OS images:</para>
<orderedlist>
<listitem><para>OS disk images containing a GPT partition table envelope, with partitions marked
according to the <ulink url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions
Specification</ulink>.</para></listitem>
<listitem><para>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.)</para></listitem>
<listitem><para>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.)</para></listitem>
</orderedlist>
<para>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 <citerefentry><refentrytitle>system-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
<option>--image=</option> switch, and be used as root file system for system service using the
<varname>RootImage=</varname> unit file setting, see
<citerefentry><refentrytitle>system.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
</refsect1>
<refsect1>
<title>Commands</title>
<para>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.</para>
<variablelist>
<varlistentry>
<term><option>--mount</option></term>
<term><option>-m</option></term>
<listitem><para>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 <ulink
url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions Specification</ulink>
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.</para>
<para>To unmount an OS image mounted like this use <citerefentry
project='man-pages'><refentrytitle>umount</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
<option>-R</option> switch (for recursive operation), so that the OS image and all nested partition
mounts are unmounted.</para>
<para>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.</para>
<para>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.)</para>
<para>All mounted file systems are checked with the appropriate <citerefentry
project='man-pages'><refentrytitle>fsck</refentrytitle><manvolnum>8</manvolnum></citerefentry>
implementation in automatic fixing mode, unless explicitly turned off (<option>--fsck=no</option>) or
read-only operation is requested (<option>--read-only</option>).</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-M</option></term>
<listitem><para>This is a shortcut for <option>--mount --mkdir</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--copy-from</option></term>
<term><option>-x</option></term>
<listitem><para>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
(<literal>-</literal>), 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.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--copy-to</option></term>
<term><option>-a</option></term>
<listitem><para>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
(<literal>-</literal>), 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.</para>
<para>As with <option>--mount</option> file system checks are implicitly run before the copy
operation begins.</para></listitem>
</varlistentry>
<xi:include href="standard-options.xml" xpointer="help" />
<xi:include href="standard-options.xml" xpointer="version" />
</variablelist>
</refsect1>
<refsect1>
<title>Options</title>
<para>The following options are understood:</para>
<variablelist>
<varlistentry>
<term><option>--read-only</option></term>
<term><option>-r</option></term>
<listitem><para>Operate in read-only mode. By default <option>--mount</option> will establish
writable mount points. If this option is specified they are established in read-only mode
instead.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--fsck=no</option></term>
<listitem><para>Turn off automatic file system checking. By default when an image is accessed for
writing (by <option>--mount</option> or <option>--add</option>) the file systems contained in the OS
image are automatically checked using the appropriate <citerefentry
project='man-pages'><refentrytitle>fsck</refentrytitle><manvolnum>8</manvolnum></citerefentry>
command, in automatic fixing mode. This behavior may be switched off using
<option>--fsck=no</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--mkdir</option></term>
<listitem><para>If combined with <option>--mount</option> 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.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--discard=</option></term>
<listitem><para>Takes one of <literal>disabled</literal>, <literal>loop</literal>,
<literal>all</literal>, <literal>crypto</literal>. If <literal>disabled</literal> the image is
accessed with empty block discarding turned off. if <literal>loop</literal> discarding is enabled if
operating on a regular file. If <literal>crypt</literal> discarding is enabled even on encrypted file
systems. If <literal>all</literal> discarding is unconditionally enabled.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--root-hash=</option></term>
<term><option>--root-hash-sig=</option></term>
<term><option>--verity-data=</option></term>
<listitem><para>Configure various aspects of Verity data integrity for the OS
image. <option>--root-hash=</option> expects a hex-encoding top-level Verity hash to use for setting
up the Verity integrity protection. <option>--root-hash-sig=</option> expects the path to a file
containing a PKCS#7 signature file 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=</option> expects the 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 <ulink
url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions Specification</ulink>.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Exit status</title>
<para>On success, 0 is returned, a non-zero failure code
otherwise.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>system-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>system.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<ulink url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions Specification</ulink>,
<citerefentry project='man-pages'><refentrytitle>umount</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>