systemd/man/systemd-gpt-auto-generator.xml

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<refentry id="systemd-gpt-auto-generator">

  <refentryinfo>
    <title>systemd-gpt-auto-generator</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>Developer</contrib>
        <firstname>Lennart</firstname>
        <surname>Poettering</surname>
        <email>lennart@poettering.net</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>systemd-gpt-auto-generator</refentrytitle>
    <manvolnum>8</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd-gpt-auto-generator</refname>
    <refpurpose>Generator for automatically discovering
    and mounting root, <filename>/home</filename> and
    <filename>/srv</filename> partitions, as well as
    discovering and enabling swap partitions, based on GPT
    partition type GUIDs.</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para><filename>/usr/lib/systemd/system-generators/systemd-gpt-auto-generator</filename></para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><filename>systemd-gpt-auto-generator</filename> is a unit
    generator that automatically discovers root,
    <filename>/home</filename>, <filename>/srv</filename> and swap
    partitions and creates mount and swap units for them, based on the
    partition type GUIDs of GUID partition tables (GPT). It implements
    the <ulink
    url="http://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/">Discoverable
    Partitions Specification</ulink>. Note that this generator has no
    effect on non-GPT systems, or where the directories under the
    mount points are already non-empty. Also, on systems where the
    units are explicitly configured (for example, listed in
    <citerefentry
    project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>),
    the units this generator creates are overriden, but additional
    automatic dependencies might be created.</para>

    <para>This generator will only look for root partitions on the
    same physical disk the EFI System Partition (ESP) is located on.
    It will only look for the other partitions on the same physical
    disk the root file system is located on. These partitions will not
    be searched on systems where the root file system is distributed
    on multiple disks, for example via btrfs RAID.</para>

    <para><filename>systemd-gpt-auto-generator</filename> is useful
    for centralizing file system configuration in the partition table
    and making manual configuration in <filename>/etc/fstab</filename>
    or suchlike unnecessary.</para>

    <para>This generator looks for the partitions based on their
    partition type GUID. The following partition type GUIDs are
    identified:</para>

    <table>
      <title>Partition Type GUIDs</title>
      <tgroup cols='3' align='left' colsep='1' rowsep='1'>
        <colspec colname="guid" />
        <colspec colname="name" />
        <colspec colname="explanation" />
        <thead>
          <row>
            <entry>Partition Type GUID</entry>
            <entry>Name</entry>
            <entry>Explanation</entry>
          </row>
        </thead>
        <tbody>
          <row>
            <entry>44479540-f297-41b2-9af7-d131d5f0458a</entry>
            <entry><filename>Root Partition (x86)</filename></entry>
            <entry>On 32-bit x86 systems, the first x86 root partition on the disk the EFI ESP is located on is mounted to the root directory <filename>/</filename>.</entry>
          </row>
          <row>
            <entry>4f68bce3-e8cd-4db1-96e7-fbcaf984b709</entry>
            <entry><filename>Root Partition (x86-64)</filename></entry>
            <entry>On 64-bit x86 systems, the first x86-64 root partition on the disk the EFI ESP is located on is mounted to the root directory <filename>/</filename>.</entry>
          </row>
          <row>
            <entry>69dad710-2ce4-4e3c-b16c-21a1d49abed3</entry>
            <entry><filename>Root Partition (32-bit ARM)</filename></entry>
            <entry>On 32-bit ARM systems, the first ARM root partition on the disk the EFI ESP is located on is mounted to the root directory <filename>/</filename>.</entry>
          </row>
          <row>
            <entry>b921b045-1df0-41c3-af44-4c6f280d3fae</entry>
            <entry><filename>Root Partition (64-bit ARM)</filename></entry>
            <entry>On 64-bit ARM systems, the first ARM root partition on the disk the EFI ESP is located on is mounted to the root directory <filename>/</filename>.</entry>
          </row>
          <row>
            <entry>933ac7e1-2eb4-4f13-b844-0e14e2aef915</entry>
            <entry>Home Partition</entry>
            <entry>The first home partition on the disk the root partition is located on is mounted to <filename>/home</filename>.</entry>
          </row>
          <row>
            <entry>3b8f8425-20e0-4f3b-907f-1a25a76f98e8</entry>
            <entry>Server Data Partition</entry>
            <entry>The first server data partition on the disk the root partition is located on is mounted to <filename>/srv</filename>.</entry>
          </row>
          <row>
            <entry>0657fd6d-a4ab-43c4-84e5-0933c84b4f4f</entry>
            <entry>Swap</entry>
            <entry>All swap partitions located on the disk the root partition is located on are enabled.</entry>
          </row>
        </tbody>
      </tgroup>
    </table>

    <para>The <filename>/home</filename> and <filename>/srv</filename>
    partitions may be encrypted in LUKS format. In this case a device
    mapper device is set up under the names
    <filename>/dev/mapper/home</filename> and
    <filename>/dev/mapper/srv</filename>. Note that this might create
    conflicts if the same partition is listed in
    <filename>/etc/crypttab</filename> with a different device mapper
    device name.</para>

    <para>Mount and automount units for the EFI System Partition (ESP),
    mounting it to <filename>/boot</filename> are generated on EFI
    systems, where the boot loader communicates the used ESP to the operating
    system. Since this generator creates an automount unit, the mount will
    only be activated on-demand, when accessed. On systems where
    <filename>/boot</filename> is an explicitly configured mount
    (for example, listed in
    <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
    or where the <filename>/boot</filename> mount point is non-empty, no
    mount units are generated.</para>

    <para>When using this generator in conjunction with btrfs file
    systems, make sure to set the correct default subvolumes on them,
    using <command>btrfs subvolume set-default</command>.</para>

    <para><filename>systemd-gpt-auto-generator</filename> implements
    <citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
      <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
      <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry project='man-pages'><refentrytitle>btrfs</refentrytitle><manvolnum>8</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>