1SYSTEMD-GPT-AUTO-GENERATOR(s8y)stemd-gpt-auto-generatSoYrSTEMD-GPT-AUTO-GENERATOR(8)
2
6 systemd-gpt-auto-generator - Generator for automatically discovering
7 and mounting root, /home and /srv partitions, as well as discovering
8 and enabling swap partitions, based on GPT partition type GUIDs.
9
11 /usr/lib/systemd/system-generators/systemd-gpt-auto-generator
12
14 systemd-gpt-auto-generator is a unit generator that automatically
15 discovers root, /home/, /srv/, the EFI System Partition, the Extended
16 Boot Loader Partition and swap partitions and creates mount and swap
17 units for them, based on the partition type GUIDs of GUID partition
18 tables (GPT), see UEFI Specification[1], chapter 5. It implements the
19 Discoverable Partitions Specification[2]. Note that this generator has
20 no effect on non-GPT systems, and on specific mount points that are
21 directories already containing files. Also, on systems where the units
22 are explicitly configured (for example, listed in fstab(5)), the units
23 this generator creates are overridden, but additional implicit
24 dependencies might be created.
25 This generator will only look for root partitions on the same physical
27 disk the EFI System Partition (ESP) is located on. It will only look
28 for the other partitions on the same physical disk the root file system
29 is located on. These partitions will not be searched for on systems
30 where the root file system is distributed on multiple disks, for
31 example via btrfs RAID.
32 systemd-gpt-auto-generator is useful for centralizing file system
34 configuration in the partition table and making configuration in
35 /etc/fstab unnecessary.
36 This generator looks for the partitions based on their partition type
38 GUID. The following partition type GUIDs are identified:
39 Table 1. Partition Type GUIDs
41 ┌─────────────────────────────────────┬──────────────────┬─────────────────┬──────────────────┐
42 │Partition Type │ Name │ Mount Point │ Explanation │
43 │GUID │ │ │ │
44 ├─────────────────────────────────────┼──────────────────┼─────────────────┼──────────────────┤
45 │44479540-f297-41b2-9af7-d131d5f0458a │ Root Partition │ / │ On 32-bit x86 │
46 │ │ (x86) │ │ systems, the │
47 │ │ │ │ first x86 root │
48 │ │ │ │ partition on the │
49 │ │ │ │ disk the EFI ESP │
50 │ │ │ │ is located on is │
51 │ │ │ │ mounted to the │
52 │ │ │ │ root directory │
53 │ │ │ │ /. │
54 ├─────────────────────────────────────┼──────────────────┼─────────────────┼──────────────────┤
55 │4f68bce3-e8cd-4db1-96e7-fbcaf984b709 │ Root Partition │ / │ On 64-bit x86 │
56 │ │ (x86-64) │ │ systems, the │
57 │ │ │ │ first x86-64 │
58 │ │ │ │ root partition │
59 │ │ │ │ on the disk the │
60 │ │ │ │ EFI ESP is │
61 │ │ │ │ located on is │
62 │ │ │ │ mounted to the │
63 │ │ │ │ root directory │
64 │ │ │ │ /. │
65 ├─────────────────────────────────────┼──────────────────┼─────────────────┼──────────────────┤
66 │69dad710-2ce4-4e3c-b16c-21a1d49abed3 │ Root Partition │ / │ On 32-bit ARM │
67 │ │ (32-bit ARM) │ │ systems, the │
68 │ │ │ │ first ARM root │
69 │ │ │ │ partition on the │
70 │ │ │ │ disk the EFI ESP │
71 │ │ │ │ is located on is │
72 │ │ │ │ mounted to the │
73 │ │ │ │ root directory │
74 │ │ │ │ /. │
75 ├─────────────────────────────────────┼──────────────────┼─────────────────┼──────────────────┤
76 │b921b045-1df0-41c3-af44-4c6f280d3fae │ Root Partition │ / │ On 64-bit ARM │
77 │ │ (64-bit ARM) │ │ systems, the │
78 │ │ │ │ first ARM root │
79 │ │ │ │ partition on the │
80 │ │ │ │ disk the EFI ESP │
81 │ │ │ │ is located on is │
82 │ │ │ │ mounted to the │
83 │ │ │ │ root directory │
84 │ │ │ │ /. │
85 ├─────────────────────────────────────┼──────────────────┼─────────────────┼──────────────────┤
86 │993d8d3d-f80e-4225-855a-9daf8ed7ea97 │ Root Partition │ / │ On Itanium │
87 │ │ (Itanium/IA-64) │ │ systems, the │
88 │ │ │ │ first Itanium │
89 │ │ │ │ root partition │
90 │ │ │ │ on the disk the │
91 │ │ │ │ EFI ESP is │
92 │ │ │ │ located on is │
93 │ │ │ │ mounted to the │
94 │ │ │ │ root directory │
95 │ │ │ │ /. │
96 ├─────────────────────────────────────┼──────────────────┼─────────────────┼──────────────────┤
97 │933ac7e1-2eb4-4f13-b844-0e14e2aef915 │ Home Partition │ /home/ │ The first home │
98 │ │ │ │ partition on the │
99 │ │ │ │ disk the root │
100 │ │ │ │ partition is │
101 │ │ │ │ located on is │
102 │ │ │ │ mounted to │
103 │ │ │ │ /home. │
104 ├─────────────────────────────────────┼──────────────────┼─────────────────┼──────────────────┤
105 │3b8f8425-20e0-4f3b-907f-1a25a76f98e8 │ Server Data │ /srv/ │ The first server │
106 │ │ Partition │ │ data partition │
107 │ │ │ │ on the disk the │
108 │ │ │ │ root partition │
109 │ │ │ │ is located on is │
110 │ │ │ │ mounted to /srv. │
111 ├─────────────────────────────────────┼──────────────────┼─────────────────┼──────────────────┤
112 │0657fd6d-a4ab-43c4-84e5-0933c84b4f4f │ Swap │ n/a │ All swap │
113 │ │ │ │ partitions │
114 │ │ │ │ located on the │
115 │ │ │ │ disk the root │
116 │ │ │ │ partition is │
117 │ │ │ │ located on are │
118 │ │ │ │ enabled. │
119 ├─────────────────────────────────────┼──────────────────┼─────────────────┼──────────────────┤
120 │c12a7328-f81f-11d2-ba4b-00a0c93ec93b │ EFI System │ /efi/ or /boot/ │ The first ESP │
121 │ │ Partition (ESP) │ │ located on the │
122 │ │ │ │ disk the root │
123 │ │ │ │ partition is │
124 │ │ │ │ located on is │
125 │ │ │ │ mounted to /boot │
126 │ │ │ │ or /efi, see │
127 │ │ │ │ below. │
128 ├─────────────────────────────────────┼──────────────────┼─────────────────┼──────────────────┤
129 │bc13c2ff-59e6-4262-a352-b275fd6f7172 │ Extended Boot │ /boot/ │ The first │
130 │ │ Loader Partition │ │ Extended Boot │
131 │ │ │ │ Loader Partition │
132 │ │ │ │ is mounted to │
133 │ │ │ │ /boot, see │
134 │ │ │ │ below. │
135 └─────────────────────────────────────┴──────────────────┴─────────────────┴──────────────────┘
136 This generator understands the following attribute flags for
138 partitions:
139 Table 2. Partition Attributes
141 ┌──────────────────────────────┬────────────────────┬─────────────────┬──────────────────┐
142 │Name │ Value │ Applicable to │ Explanation │
143 ├──────────────────────────────┼────────────────────┼─────────────────┼──────────────────┤
144 │GPT_FLAG_READ_ONLY │ 0x1000000000000000 │ /, /home/, │ Partition is │
145 │ │ │ /srv/, Extended │ mounted │
146 │ │ │ Boot Loader │ read-only │
147 │ │ │ Partition │ │
148 ├──────────────────────────────┼────────────────────┼─────────────────┼──────────────────┤
149 │GPT_FLAG_NO_AUTO │ 0x8000000000000000 │ /, /home/, │ Partition is not │
150 │ │ │ /srv/, Extended │ mounted │
151 │ │ │ Boot Loader │ automatically │
152 │ │ │ Partition │ │
153 ├──────────────────────────────┼────────────────────┼─────────────────┼──────────────────┤
154 │GPT_FLAG_NO_BLOCK_IO_PROTOCOL │ 0x0000000000000002 │ EFI System │ Partition is not │
155 │ │ │ Partition (ESP) │ mounted │
156 │ │ │ │ automatically │
157 └──────────────────────────────┴────────────────────┴─────────────────┴──────────────────┘
158 The /home/ and /srv/ partitions may be encrypted in LUKS format. In
160 this case, a device mapper device is set up under the names
161 /dev/mapper/home and /dev/mapper/srv. Note that this might create
162 conflicts if the same partition is listed in /etc/crypttab with a
163 different device mapper device name.
164 When systemd is running in the initrd the / partition may be encrypted
166 in LUKS format as well. In this case, a device mapper device is set up
167 under the name /dev/mapper/root, and a sysroot.mount is set up that
168 mounts the device under /sysroot. For more information, see bootup(7).
169 Mount and automount units for the EFI System Partition (ESP) are
171 generated on EFI systems. The ESP is mounted to /boot/ (except if an
172 Extended Boot Loader partition exists, see below), unless a mount point
173 directory /efi/ exists, in which case it is mounted there. Since this
174 generator creates an automount unit, the mount will only be activated
175 on-demand, when accessed. On systems where /boot/ (or /efi/ if it
176 exists) is an explicitly configured mount (for example, listed in
177 fstab(5)) or where the /boot/ (or /efi/) mount point is non-empty, no
178 mount units are generated.
179 If the disk contains an Extended Boot Loader partition, as defined in
181 the Boot Loader Specification[3], it is made available at /boot (by
182 means of an automount point, similar to the ESP, see above). If both an
183 EFI System Partition and an Extended Boot Loader partition exist the
184 latter is preferably mounted to /boot/. Make sure to create both /efi/
185 and /boot/ to ensure both partitions are mounted.
186 When using this generator in conjunction with btrfs file systems, make
188 sure to set the correct default subvolumes on them, using btrfs
189 subvolume set-default.
190 systemd-gpt-auto-generator implements systemd.generator(7).
192
194 systemd-gpt-auto-generator understands the following kernel command
195 line parameters:
196 systemd.gpt_auto, rd.systemd.gpt_auto
198 Those options take an optional boolean argument, and default to
199 yes. The generator is enabled by default, and a negative value may
200 be used to disable it.
201 root=
203 When used with the special value "gpt-auto", automatic discovery of
204 the root partition based on the GPT partition type is enabled. Any
205 other value disables this generator.
206 rw, ro
208 Mount the root partition read-write or read-only initially.
209 Note that unlike most kernel command line options these settings do
211 not override configuration in the file system, and the file system
212 may be remounted later. See systemd-remount-fs.service(8).
213
215 systemd(1), systemd.mount(5), systemd.swap(5), systemd-fstab-
216 generator(8), systemd-cryptsetup@.service(8), cryptsetup(8), fstab(5),
217 btrfs(8)
218
220 1. UEFI Specification
221 https://uefi.org/specifications
222 2. Discoverable Partitions Specification
224 https://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/
225 3. Boot Loader Specification
227 https://systemd.io/BOOT_LOADER_SPECIFICATION
228systemd 243 SYSTEMD-GPT-AUTO-GENERATOR(8)