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