man/systemd-gpt-auto-generator.xml

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   5   SPDX-License-Identifier: LGPL-2.1+
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   7 <refentry id="systemd-gpt-auto-generator">
   8
   9   <refentryinfo>
  10     <title>systemd-gpt-auto-generator</title>
  11     <productname>systemd</productname>
  12
  13     <authorgroup>
  14       <author>
  15         <contrib>Developer</contrib>
  16         <firstname>Lennart</firstname>
  17         <surname>Poettering</surname>
  18         <email>lennart@poettering.net</email>
  19       </author>
  20     </authorgroup>
  21   </refentryinfo>
  22
  23   <refmeta>
  24     <refentrytitle>systemd-gpt-auto-generator</refentrytitle>
  25     <manvolnum>8</manvolnum>
  26   </refmeta>
  27
  28   <refnamediv>
  29     <refname>systemd-gpt-auto-generator</refname>
  30     <refpurpose>Generator for automatically discovering
  31     and mounting root, <filename>/home</filename> and
  32     <filename>/srv</filename> partitions, as well as
  33     discovering and enabling swap partitions, based on GPT
  34     partition type GUIDs.</refpurpose>
  35   </refnamediv>
  36
  37   <refsynopsisdiv>
  38     <para><filename>/usr/lib/systemd/system-generators/systemd-gpt-auto-generator</filename></para>
  39   </refsynopsisdiv>
  40
  41   <refsect1>
  42     <title>Description</title>
  43
  44     <para><filename>systemd-gpt-auto-generator</filename> is a unit
  45     generator that automatically discovers root,
  46     <filename>/home</filename>, <filename>/srv</filename> and swap
  47     partitions and creates mount and swap units for them, based on the
  48     partition type GUIDs of GUID partition tables (GPT),
  49     see <ulink url="http://www.uefi.org/specifications">UEFI Specification</ulink>, chapter 5.
  50     It implements the <ulink
  51     url="https://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/">Discoverable
  52     Partitions Specification</ulink>. Note that this generator has no
  53     effect on non-GPT systems, or where the directories under the
  54     mount points are already non-empty. Also, on systems where the
  55     units are explicitly configured (for example, listed in
  56     <citerefentry
  57     project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>),
  58     the units this generator creates are overridden, but additional
  59     implicit dependencies might be created.</para>
  60
  61     <para>This generator will only look for root partitions on the
  62     same physical disk the EFI System Partition (ESP) is located on.
  63     It will only look for the other partitions on the same physical
  64     disk the root file system is located on. These partitions will not
  65     be searched for on systems where the root file system is distributed
  66     on multiple disks, for example via btrfs RAID.</para>
  67
  68     <para><filename>systemd-gpt-auto-generator</filename> is useful
  69     for centralizing file system configuration in the partition table
  70     and making configuration in <filename>/etc/fstab</filename> unnecessary.
  71     </para>
  72
  73     <para>This generator looks for the partitions based on their
  74     partition type GUID. The following partition type GUIDs are
  75     identified:</para>
  76
  77     <table>
  78       <title>Partition Type GUIDs</title>
  79       <tgroup cols='3' align='left' colsep='1' rowsep='1'>
  80         <colspec colname="guid" />
  81         <colspec colname="name" />
  82         <colspec colname="explanation" />
  83         <thead>
  84           <row>
  85             <entry>Partition Type GUID</entry>
  86             <entry>Name</entry>
  87             <entry>Explanation</entry>
  88           </row>
  89         </thead>
  90         <tbody>
  91           <row>
  92             <entry>44479540-f297-41b2-9af7-d131d5f0458a</entry>
  93             <entry><filename>Root Partition (x86)</filename></entry>
  94             <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>
  95           </row>
  96           <row>
  97             <entry>4f68bce3-e8cd-4db1-96e7-fbcaf984b709</entry>
  98             <entry><filename>Root Partition (x86-64)</filename></entry>
  99             <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>
 100           </row>
 101           <row>
 102             <entry>69dad710-2ce4-4e3c-b16c-21a1d49abed3</entry>
 103             <entry><filename>Root Partition (32-bit ARM)</filename></entry>
 104             <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>
 105           </row>
 106           <row>
 107             <entry>b921b045-1df0-41c3-af44-4c6f280d3fae</entry>
 108             <entry><filename>Root Partition (64-bit ARM)</filename></entry>
 109             <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>
 110           </row>
 111           <row>
 112             <entry>993d8d3d-f80e-4225-855a-9daf8ed7ea97</entry>
 113             <entry><filename>Root Partition (Itanium/IA-64)</filename></entry>
 114             <entry>On Itanium systems, the first Itanium root partition on the disk the EFI ESP is located on is mounted to the root directory <filename>/</filename>.</entry>
 115           </row>
 116           <row>
 117             <entry>933ac7e1-2eb4-4f13-b844-0e14e2aef915</entry>
 118             <entry>Home Partition</entry>
 119             <entry>The first home partition on the disk the root partition is located on is mounted to <filename>/home</filename>.</entry>
 120           </row>
 121           <row>
 122             <entry>3b8f8425-20e0-4f3b-907f-1a25a76f98e8</entry>
 123             <entry>Server Data Partition</entry>
 124             <entry>The first server data partition on the disk the root partition is located on is mounted to <filename>/srv</filename>.</entry>
 125           </row>
 126           <row>
 127             <entry>0657fd6d-a4ab-43c4-84e5-0933c84b4f4f</entry>
 128             <entry>Swap</entry>
 129             <entry>All swap partitions located on the disk the root partition is located on are enabled.</entry>
 130           </row>
 131           <row>
 132             <entry>c12a7328-f81f-11d2-ba4b-00a0c93ec93b</entry>
 133             <entry>EFI System Partition (ESP)</entry>
 134             <entry>The first ESP located on the disk the root partition is located on is mounted to <filename>/boot</filename> or <filename>/efi</filename>, see below.</entry>
 135           </row>
 136         </tbody>
 137       </tgroup>
 138     </table>
 139
 140     <para>This generator understands the following attribute flags for partitions:</para>
 141
 142     <table>
 143       <title>Partition Attributes</title>
 144       <tgroup cols='4' align='left' colsep='1' rowsep='1'>
 145         <colspec colname="attribute" />
 146         <colspec colname="value" />
 147         <colspec colname="where" />
 148         <colspec colname="explanation" />
 149         <thead>
 150           <row>
 151             <entry>Name</entry>
 152             <entry>Value</entry>
 153             <entry>Applicable to</entry>
 154             <entry>Explanation</entry>
 155           </row>
 156         </thead>
 157         <tbody>
 158           <row>
 159             <entry><constant>GPT_FLAG_READ_ONLY</constant></entry>
 160             <entry>0x1000000000000000</entry>
 161             <entry><filename>/</filename>, <filename>/srv</filename>, <filename>/home</filename></entry>
 162             <entry>Partition is mounted read-only</entry>
 163           </row>
 164
 165           <row>
 166             <entry><constant>GPT_FLAG_NO_AUTO</constant></entry>
 167             <entry>0x8000000000000000</entry>
 168             <entry><filename>/</filename>, <filename>/srv</filename>, <filename>/home</filename></entry>
 169             <entry>Partition is not mounted automatically</entry>
 170           </row>
 171
 172           <row>
 173             <entry><constant>GPT_FLAG_NO_BLOCK_IO_PROTOCOL</constant></entry>
 174             <entry>0x0000000000000002</entry>
 175             <entry>ESP</entry>
 176             <entry>Partition is not mounted automatically</entry>
 177           </row>
 178         </tbody>
 179       </tgroup>
 180     </table>
 181
 182     <para>The <filename>/home</filename> and <filename>/srv</filename>
 183     partitions may be encrypted in LUKS format. In this case, a device
 184     mapper device is set up under the names
 185     <filename>/dev/mapper/home</filename> and
 186     <filename>/dev/mapper/srv</filename>. Note that this might create
 187     conflicts if the same partition is listed in
 188     <filename>/etc/crypttab</filename> with a different device mapper
 189     device name.</para>
 190
 191     <para>Mount and automount units for the EFI System Partition (ESP) are generated on EFI systems. The ESP is mounted
 192     to <filename>/boot</filename>, unless a mount point directory <filename>/efi</filename> exists, in which case it is
 193     mounted there. Since this generator creates an automount unit, the mount will only be activated on-demand, when
 194     accessed. On systems where <filename>/boot</filename> (or <filename>/efi</filename> if it exists) is an explicitly
 195     configured mount (for example, listed in <citerefentry
 196     project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>) or where the
 197     <filename>/boot</filename> (or <filename>/efi</filename>) mount point is non-empty, no mount units are
 198     generated.</para>
 199
 200     <para>When using this generator in conjunction with btrfs file
 201     systems, make sure to set the correct default subvolumes on them,
 202     using <command>btrfs subvolume set-default</command>.</para>
 203
 204     <para><filename>systemd-gpt-auto-generator</filename> implements
 205     <citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 206   </refsect1>
 207
 208   <refsect1>
 209     <title>See Also</title>
 210     <para>
 211       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 212       <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 213       <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 214       <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 215       <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 216       <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 217       <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 218       <citerefentry project='man-pages'><refentrytitle>btrfs</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 219     </para>
 220   </refsect1>
 221
 222 </refentry>