3 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.5//EN"
4 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
5 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
6 <refentry id=
"systemd-gpt-auto-generator">
9 <title>systemd-gpt-auto-generator
</title>
10 <productname>systemd
</productname>
14 <refentrytitle>systemd-gpt-auto-generator
</refentrytitle>
15 <manvolnum>8</manvolnum>
19 <refname>systemd-gpt-auto-generator
</refname>
20 <refpurpose>Generator for automatically discovering
21 and mounting root,
<filename>/home
</filename> and
22 <filename>/srv
</filename> partitions, as well as
23 discovering and enabling swap partitions, based on GPT
24 partition type GUIDs.
</refpurpose>
28 <para><filename>/usr/lib/systemd/system-generators/systemd-gpt-auto-generator
</filename></para>
32 <title>Description
</title>
34 <para><filename>systemd-gpt-auto-generator
</filename> is a unit generator that automatically discovers
35 root,
<filename>/home/
</filename>,
<filename>/srv/
</filename>, the EFI System Partition, the Extended
36 Boot Loader Partition and swap partitions and creates mount and swap units for them, based on the
37 partition type GUIDs of GUID partition tables (GPT), see
<ulink
38 url=
"https://uefi.org/specifications">UEFI Specification
</ulink>, chapter
5. It implements the
<ulink
39 url=
"https://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/">Discoverable Partitions
40 Specification
</ulink>. Note that this generator has no effect on non-GPT systems, and on specific mount
41 points that are directories already containing files. Also, on systems where the units are explicitly
42 configured (for example, listed in
<citerefentry
43 project='man-pages'
><refentrytitle>fstab
</refentrytitle><manvolnum>5</manvolnum></citerefentry>), the
44 units this generator creates are overridden, but additional implicit dependencies might be
47 <para>This generator will only look for the root partition on the same physical disk the EFI System
48 Partition (ESP) is located on. Note that support from the boot loader is required: EFI variable
49 <varname>LoaderDevicePartUUID-
4a67b082-
0a4c-
41cf-b6c7-
440b29bb8c4f
</varname> is used to determine from
50 which partition, and hence the disk from which the system was booted. If the boot loader does not set
51 this variable, this generator will not be able to autodetect the root partition.
</para>
53 <para>Similarly, this generator will only look for the other partitions on the same physical disk as the
54 root partition. In this case, boot loader support is not required. These partitions will not be searched
55 for on systems where the root file system is distributed on multiple disks, for example via btrfs RAID.
58 <para><filename>systemd-gpt-auto-generator
</filename> is useful for centralizing file system
59 configuration in the partition table and making configuration in
<filename>/etc/fstab
</filename> or on
60 the kernel command line unnecessary.
</para>
62 <para>This generator looks for the partitions based on their
63 partition type GUID. The following partition type GUIDs are
67 <title>Partition Type GUIDs
</title>
68 <tgroup cols='
3' align='left' colsep='
1' rowsep='
1'
>
69 <colspec colname=
"guid" />
70 <colspec colname=
"name" />
71 <colspec colname=
"where" />
72 <colspec colname=
"explanation" />
75 <entry>Partition Type GUID
</entry>
77 <entry>Mount Point
</entry>
78 <entry>Explanation
</entry>
83 <entry>44479540-f297-
41b2-
9af7-d131d5f0458a
</entry>
84 <entry><filename>Root Partition (x86)
</filename></entry>
85 <entry><filename>/
</filename></entry>
86 <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>
89 <entry>4f68bce3-e8cd-
4db1-
96e7-fbcaf984b709
</entry>
90 <entry><filename>Root Partition (x86-
64)
</filename></entry>
91 <entry><filename>/
</filename></entry>
92 <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>
95 <entry>69dad710-
2ce4-
4e3c-b16c-
21a1d49abed3
</entry>
96 <entry><filename>Root Partition (
32-bit ARM)
</filename></entry>
97 <entry><filename>/
</filename></entry>
98 <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>
101 <entry>b921b045-
1df0-
41c3-af44-
4c6f280d3fae
</entry>
102 <entry><filename>Root Partition (
64-bit ARM)
</filename></entry>
103 <entry><filename>/
</filename></entry>
104 <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>
107 <entry>993d8d3d-f80e-4225-
855a-
9daf8ed7ea97
</entry>
108 <entry><filename>Root Partition (Itanium/IA-
64)
</filename></entry>
109 <entry><filename>/
</filename></entry>
110 <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>
113 <entry>933ac7e1-
2eb4-
4f13-b844-
0e14e2aef915
</entry>
114 <entry>Home Partition
</entry>
115 <entry><filename>/home/
</filename></entry>
116 <entry>The first home partition on the disk the root partition is located on is mounted to
<filename>/home
</filename>.
</entry>
119 <entry>3b8f8425-
20e0-
4f3b-
907f-
1a25a76f98e8
</entry>
120 <entry>Server Data Partition
</entry>
121 <entry><filename>/srv/
</filename></entry>
122 <entry>The first server data partition on the disk the root partition is located on is mounted to
<filename>/srv
</filename>.
</entry>
125 <entry>0657fd6d-a4ab-
43c4-
84e5-
0933c84b4f4f
</entry>
128 <entry>All swap partitions located on the disk the root partition is located on are enabled.
</entry>
131 <entry>c12a7328-f81f-
11d2-ba4b-
00a0c93ec93b
</entry>
132 <entry>EFI System Partition (ESP)
</entry>
133 <entry><filename>/efi/
</filename> or
<filename>/boot/
</filename></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>
137 <entry>bc13c2ff-
59e6-
4262-a352-b275fd6f7172
</entry>
138 <entry>Extended Boot Loader Partition
</entry>
139 <entry><filename>/boot/
</filename></entry>
140 <entry>The first Extended Boot Loader Partition is mounted to
<filename>/boot
</filename>, see below.
</entry>
146 <para>This generator understands the following attribute flags for partitions:
</para>
149 <title>Partition Attributes
</title>
150 <tgroup cols='
4' align='left' colsep='
1' rowsep='
1'
>
151 <colspec colname=
"attribute" />
152 <colspec colname=
"value" />
153 <colspec colname=
"where" />
154 <colspec colname=
"explanation" />
159 <entry>Applicable to
</entry>
160 <entry>Explanation
</entry>
165 <entry><constant>GPT_FLAG_READ_ONLY
</constant></entry>
166 <entry>0x1000000000000000</entry>
167 <entry><filename>/
</filename>,
<filename>/home/
</filename>,
<filename>/srv/
</filename>, Extended Boot Loader Partition
</entry>
168 <entry>Partition is mounted read-only
</entry>
172 <entry><constant>GPT_FLAG_NO_AUTO
</constant></entry>
173 <entry>0x8000000000000000</entry>
174 <entry><filename>/
</filename>,
<filename>/home/
</filename>,
<filename>/srv/
</filename>, Extended Boot Loader Partition
</entry>
175 <entry>Partition is not mounted automatically
</entry>
179 <entry><constant>GPT_FLAG_NO_BLOCK_IO_PROTOCOL
</constant></entry>
180 <entry>0x0000000000000002</entry>
181 <entry>EFI System Partition (ESP)
</entry>
182 <entry>Partition is not mounted automatically
</entry>
188 <para>The
<filename>/home/
</filename> and
<filename>/srv/
</filename> partitions may be encrypted in LUKS
189 format. In this case, a device mapper device is set up under the names
190 <filename>/dev/mapper/home
</filename> and
<filename>/dev/mapper/srv
</filename>. Note that this might
191 create conflicts if the same partition is listed in
<filename>/etc/crypttab
</filename> with a different
192 device mapper device name.
</para>
194 <para>When systemd is running in the initrd the
<filename>/
</filename> partition may be encrypted in LUKS
195 format as well. In this case, a device mapper device is set up under the name
<filename>/dev/mapper/root
</filename>,
196 and a
<filename>sysroot.mount
</filename> is set up that mounts the device under
<filename>/sysroot
</filename>.
197 For more information, see
<citerefentry><refentrytitle>bootup
</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
200 <para>Mount and automount units for the EFI System Partition (ESP) are generated on EFI systems. The ESP
201 is mounted to
<filename>/boot/
</filename> (except if an Extended Boot Loader partition exists, see
202 below), unless a mount point directory
<filename>/efi/
</filename> exists, in which case it is mounted
203 there. Since this generator creates an automount unit, the mount will only be activated on-demand, when
204 accessed. On systems where
<filename>/boot/
</filename> (or
<filename>/efi/
</filename> if it exists) is an
205 explicitly configured mount (for example, listed in
<citerefentry
206 project='man-pages'
><refentrytitle>fstab
</refentrytitle><manvolnum>5</manvolnum></citerefentry>) or where
207 the
<filename>/boot/
</filename> (or
<filename>/efi/
</filename>) mount point is non-empty, no mount units
208 are generated.
</para>
210 <para>If the disk contains an Extended Boot Loader partition, as defined in the
<ulink
211 url=
"https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification
</ulink>, it is made
212 available at
<filename>/boot
</filename> (by means of an automount point, similar to the ESP, see
213 above). If both an EFI System Partition and an Extended Boot Loader partition exist the latter is
214 preferably mounted to
<filename>/boot/
</filename>. Make sure to create both
<filename>/efi/
</filename>
215 and
<filename>/boot/
</filename> to ensure both partitions are mounted.
</para>
217 <para>When using this generator in conjunction with btrfs file
218 systems, make sure to set the correct default subvolumes on them,
219 using
<command>btrfs subvolume set-default
</command>.
</para>
221 <para><filename>systemd-gpt-auto-generator
</filename> implements
222 <citerefentry><refentrytitle>systemd.generator
</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
</para>
226 <title>Kernel Command Line
</title>
228 <para><filename>systemd-gpt-auto-generator
</filename> understands the following kernel command line
231 <variablelist class='kernel-commandline-options'
>
234 <term><varname>systemd.gpt_auto
</varname></term>
235 <term><varname>rd.systemd.gpt_auto
</varname></term>
237 <listitem><para>Those options take an optional boolean argument, and default to yes.
238 The generator is enabled by default, and a negative value may be used to disable it.
243 <term><varname>root=
</varname></term>
245 <listitem><para>When used with the special value
<literal>gpt-auto
</literal>, automatic discovery of
246 the root partition based on the GPT partition type is enabled. Any other value disables this
247 generator.
</para></listitem>
251 <term><varname>rw
</varname></term>
252 <term><varname>ro
</varname></term>
254 <listitem><para>Mount the root partition read-write or read-only
<emphasis>initially
</emphasis>.
</para>
256 <para>Note that unlike most kernel command line options these settings do not override configuration
257 in the file system, and the file system may be remounted later. See
258 <citerefentry><refentrytitle>systemd-remount-fs.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
265 <title>See Also
</title>
267 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
268 <citerefentry><refentrytitle>systemd.mount
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
269 <citerefentry><refentrytitle>systemd.swap
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
270 <citerefentry><refentrytitle>systemd-fstab-generator
</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
271 <citerefentry><refentrytitle>systemd-cryptsetup@.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
272 <citerefentry project='die-net'
><refentrytitle>cryptsetup
</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
273 <citerefentry project='man-pages'
><refentrytitle>fstab
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
274 <citerefentry project='man-pages'
><refentrytitle>btrfs
</refentrytitle><manvolnum>8</manvolnum></citerefentry>