systemd/man/systemd-dissect.xml

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<refentry id="systemd-dissect" conditional='HAVE_BLKID'
    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>systemd-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>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>

    <para>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 <filename>/usr/</filename>
    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 <citerefentry
    project='man-pages'><refentrytitle>fdisk</refentrytitle><manvolnum>8</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>

      <varlistentry>
        <term><option>--json=</option><replaceable>MODE</replaceable></term>

        <listitem><para>Shows output formatted as JSON. Expects one of <literal>short</literal> (for the
        shortest possible output without any redundant whitespace or line breaks), <literal>pretty</literal>
        (for a pretty version of the same, with indentation and line breaks) or <literal>off</literal> (to turn
        off json output).</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>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.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>,
      <citerefentry project='man-pages'><refentrytitle>fdisk</refentrytitle><manvolnum>8</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>