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/, /srv/, /var/ and /var/tmp/ partitions, as
8 well as discovering and enabling swap partitions, based on GPT
9 partition type GUIDs
10
12 /usr/lib/systemd/system-generators/systemd-gpt-auto-generator
13
15 systemd-gpt-auto-generator is a unit generator that automatically
16 discovers the root partition, /home/, /srv/, /var/, /var/tmp/, the EFI
17 System Partition, the Extended Boot Loader Partition, and swap
18 partitions and creates mount and swap units for them, based on the
19 partition type GUIDs of GUID partition tables (GPT). See UEFI
20 Specification[1], chapter 5 for more details. It implements the
21 Discoverable Partitions Specification[2].
22 Note that this generator has no effect on non-GPT systems. It will also
24 not create mount point configuration for directories which already
25 contain files or if the mount point is explicitly configured in
26 fstab(5). If the units this generator creates are overridden, for
27 example by units in directories with higher precedence, drop-ins and
28 additional dependencies created by this generator might still be used.
29 This generator will only look for the root partition on the same
31 physical disk where the EFI System Partition (ESP) is located. Note
32 that support from the boot loader is required: the EFI variable
33 LoaderDevicePartUUID of the 4a67b082-0a4c-41cf-b6c7-440b29bb8c4f vendor
34 UUID is used to determine from which partition, and hence the disk,
35 from which the system was booted. If the boot loader does not set this
36 variable, this generator will not be able to detect the root partition.
37 See the Boot Loader Interface[3] for details.
38 Similarly, this generator will only look for the other partitions on
40 the same physical disk as the root partition. In this case, boot loader
41 support is not required. These partitions will not be searched for on
42 systems where the root file system is distributed on multiple disks,
43 for example via btrfs RAID.
44 systemd-gpt-auto-generator is useful for centralizing file system
46 configuration in the partition table and making configuration in
47 /etc/fstab or on the kernel command line unnecessary.
48 This generator looks for the partitions based on their partition type
50 GUID. The following partition type GUIDs are identified:
51 Table 1. Partition Type GUIDs
53 ┌─────────────────────────────────────┬──────────────────┬─────────────────┬───────────────────┐
54 │Partition Type │ Name │ Mount Point │ Explanation │
55 │GUID │ │ │ │
56 ├─────────────────────────────────────┼──────────────────┼─────────────────┼───────────────────┤
57 │SD_GPT_ROOT_X86_64 │ Root Partition │ / │ The first │
58 │4f68bce3-e8cd-4db1-96e7-fbcaf984b709 │ (x86-64) │ │ partition with │
59 │ │ │ │ this type UUID, │
60 │ │ │ │ located on the │
61 │ │ │ │ same disk as the │
62 │ │ │ │ ESP, is used as │
63 │ │ │ │ the root file │
64 │ │ │ │ system / on │
65 │ │ │ │ AMD64 / 64-bit │
66 │ │ │ │ x86 systems. │
67 ├─────────────────────────────────────┼──────────────────┼─────────────────┼───────────────────┤
68 │SD_GPT_ROOT_ARM64 │ Root Partition │ / │ The first │
69 │b921b045-1df0-41c3-af44-4c6f280d3fae │ (64-bit ARM) │ │ partition with │
70 │ │ │ │ this type UUID, │
71 │ │ │ │ located on the │
72 │ │ │ │ same disk as the │
73 │ │ │ │ ESP, is used as │
74 │ │ │ │ the root file │
75 │ │ │ │ system / on │
76 │ │ │ │ AArch64 / 64-bit │
77 │ │ │ │ ARM systems. │
78 ├─────────────────────────────────────┼──────────────────┼─────────────────┼───────────────────┤
79 │SD_GPT_ROOT_ALPHA SD_GPT_ROOT_ARC │ root partitions │ / │ The first │
80 │SD_GPT_ROOT_ARM SD_GPT_ROOT_ARM64 │ for other │ │ partition with │
81 │SD_GPT_ROOT_IA64 │ architectures │ │ the type UUID │
82 │SD_GPT_ROOT_LOONGARCH64 │ │ │ matching the │
83 │SD_GPT_ROOT_MIPS SD_GPT_ROOT_MIPS64 │ │ │ architecture, │
84 │SD_GPT_ROOT_MIPS_LE │ │ │ located on the │
85 │SD_GPT_ROOT_MIPS64_LE │ │ │ same disk as the │
86 │SD_GPT_ROOT_PARISC SD_GPT_ROOT_PPC │ │ │ ESP, is used as │
87 │SD_GPT_ROOT_PPC64 │ │ │ the root file │
88 │SD_GPT_ROOT_PPC64_LE │ │ │ system /. For │
89 │SD_GPT_ROOT_RISCV32 │ │ │ the full list │
90 │SD_GPT_ROOT_RISCV64 SD_GPT_ROOT_S390 │ │ │ and constant │
91 │SD_GPT_ROOT_S390X SD_GPT_ROOT_TILEGX │ │ │ values, see │
92 │SD_GPT_ROOT_X86 SD_GPT_ROOT_X86_64 │ │ │ Discoverable │
93 │SD_GPT_USR_ALPHA SD_GPT_USR_ARC │ │ │ Partitions │
94 │SD_GPT_USR_ARM SD_GPT_USR_IA64 │ │ │ Specification[2]. │
95 │SD_GPT_USR_LOONGARCH64 │ │ │ │
96 │SD_GPT_USR_MIPS_LE │ │ │ │
97 │SD_GPT_USR_MIPS64_LE │ │ │ │
98 │SD_GPT_USR_PARISC SD_GPT_USR_PPC │ │ │ │
99 │SD_GPT_USR_PPC64 SD_GPT_USR_PPC64_LE │ │ │ │
100 │SD_GPT_USR_RISCV32 │ │ │ │
101 │SD_GPT_USR_RISCV64 SD_GPT_USR_S390 │ │ │ │
102 │SD_GPT_USR_S390X SD_GPT_USR_TILEGX │ │ │ │
103 │SD_GPT_USR_X86 │ │ │ │
104 ├─────────────────────────────────────┼──────────────────┼─────────────────┼───────────────────┤
105 │SD_GPT_HOME │ Home Partition │ /home/ │ The first │
106 │933ac7e1-2eb4-4f13-b844-0e14e2aef915 │ │ │ partition with │
107 │ │ │ │ this type UUID on │
108 │ │ │ │ the same disk as │
109 │ │ │ │ the ESP is │
110 │ │ │ │ mounted to │
111 │ │ │ │ /home/. │
112 ├─────────────────────────────────────┼──────────────────┼─────────────────┼───────────────────┤
113 │SD_GPT_SRV │ Server Data │ /srv/ │ The first │
114 │3b8f8425-20e0-4f3b-907f-1a25a76f98e8 │ Partition │ │ partition with │
115 │ │ │ │ this type UUID on │
116 │ │ │ │ the same disk as │
117 │ │ │ │ the ESP is │
118 │ │ │ │ mounted to /srv/. │
119 ├─────────────────────────────────────┼──────────────────┼─────────────────┼───────────────────┤
120 │SD_GPT_VAR │ Variable Data │ /var/ │ The first │
121 │4d21b016-b534-45c2-a9fb-5c16e091fd2d │ Partition │ │ partition with │
122 │ │ │ │ this type UUID on │
123 │ │ │ │ the same disk as │
124 │ │ │ │ the ESP is │
125 │ │ │ │ mounted to /var/ │
126 │ │ │ │ — under the │
127 │ │ │ │ condition its │
128 │ │ │ │ partition UUID │
129 │ │ │ │ matches the first │
130 │ │ │ │ 128 bit of the │
131 │ │ │ │ HMAC-SHA256 of │
132 │ │ │ │ the GPT type uuid │
133 │ │ │ │ of this partition │
134 │ │ │ │ keyed by the │
135 │ │ │ │ machine ID of the │
136 │ │ │ │ installation │
137 │ │ │ │ stored in │
138 │ │ │ │ machine-id(5). │
139 ├─────────────────────────────────────┼──────────────────┼─────────────────┼───────────────────┤
140 │SD_GPT_TMP │ Temporary Data │ /var/tmp/ │ The first │
141 │7ec6f557-3bc5-4aca-b293-16ef5df639d1 │ Partition │ │ partition with │
142 │ │ │ │ this type UUID on │
143 │ │ │ │ the same disk as │
144 │ │ │ │ the ESP is │
145 │ │ │ │ mounted to │
146 │ │ │ │ /var/tmp/. │
147 ├─────────────────────────────────────┼──────────────────┼─────────────────┼───────────────────┤
148 │SD_GPT_SWAP │ Swap │ n/a │ All partitions │
149 │0657fd6d-a4ab-43c4-84e5-0933c84b4f4f │ │ │ with this type │
150 │ │ │ │ UUID on the same │
151 │ │ │ │ disk as the ESP │
152 │ │ │ │ are used as swap. │
153 ├─────────────────────────────────────┼──────────────────┼─────────────────┼───────────────────┤
154 │SD_GPT_ESP │ EFI System │ /efi/ or /boot/ │ The first │
155 │c12a7328-f81f-11d2-ba4b-00a0c93ec93b │ Partition (ESP) │ │ partition with │
156 │ │ │ │ this type UUID │
157 │ │ │ │ located on the │
158 │ │ │ │ same disk as the │
159 │ │ │ │ root partition is │
160 │ │ │ │ mounted to /boot/ │
161 │ │ │ │ or /efi/, see │
162 │ │ │ │ below. │
163 ├─────────────────────────────────────┼──────────────────┼─────────────────┼───────────────────┤
164 │SD_GPT_XBOOTLDR │ Extended Boot │ /boot/ │ The first │
165 │bc13c2ff-59e6-4262-a352-b275fd6f7172 │ Loader Partition │ │ partition with │
166 │ │ │ │ this type UUID │
167 │ │ │ │ located on the │
168 │ │ │ │ same disk as the │
169 │ │ │ │ root partition is │
170 │ │ │ │ mounted to │
171 │ │ │ │ /boot/, see │
172 │ │ │ │ below. │
173 └─────────────────────────────────────┴──────────────────┴─────────────────┴───────────────────┘
174 This generator understands the following attribute flags for
176 partitions:
177 Table 2. Partition Attribute Flags
179 ┌─────────────────────────────────┬───────────────────┬───────────────────┐
180 │Flag │ Applicable to │ Explanation │
181 ├─────────────────────────────────┼───────────────────┼───────────────────┤
182 │SD_GPT_FLAG_READ_ONLY │ /, /home/, /srv/, │ Partition is │
183 │0x1000000000000000 │ /var/, /var/tmp/, │ mounted read-only │
184 │ │ Extended Boot │ │
185 │ │ Loader Partition │ │
186 ├─────────────────────────────────┼───────────────────┼───────────────────┤
187 │SD_GPT_FLAG_NO_AUTO │ /, /home/, /srv/, │ Partition is not │
188 │0x8000000000000000 │ /var/, /var/tmp/, │ mounted │
189 │ │ Extended Boot │ automatically │
190 │ │ Loader Partition │ │
191 ├─────────────────────────────────┼───────────────────┼───────────────────┤
192 │SD_GPT_FLAG_NO_BLOCK_IO_PROTOCOL │ EFI System │ Partition is not │
193 │0x0000000000000002 │ Partition (ESP) │ mounted │
194 │ │ │ automatically │
195 └─────────────────────────────────┴───────────────────┴───────────────────┘
196 The /home/, /srv/, /var/, /var/tmp/ and swap partitions may be
198 encrypted in LUKS format. In this case, a device mapper device is set
199 up under the names /dev/mapper/home, /dev/mapper/srv, /dev/mapper/var,
200 /dev/mapper/tmp or /dev/mapper/swap. Note that this might create
201 conflicts if the same partition is listed in /etc/crypttab with a
202 different device mapper device name.
203 When systemd is running in the initrd the / partition may be encrypted
205 with LUKS as well. In this case, a device mapper device is set up under
206 the name /dev/mapper/root, and a sysroot.mount is set up that mounts
207 the device under /sysroot. For more information, see bootup(7).
208 The root partition can be specified by symlinking
210 /run/systemd/volatile-root to /dev/block/$major:$minor. This is
211 especially useful if the root mount has been replaced by some form of
212 volatile file system (overlayfs).
213 Mount and automount units for the EFI System Partition (ESP) and
215 Extended Boot Loader Partition (XBOOTLDR) are generated on EFI systems.
216 If the disk contains an XBOOTLDR partition, as defined in the Boot
217 Loader Specification[4], it is made available at /boot/. This generator
218 creates an automount unit; the mount will only be activated on-demand
219 when accessed. The mount point will be created if necessary.
220 The ESP is mounted to /boot/ if that directory exists and is not used
222 for XBOOTLDR, and otherwise to /efi/. Same as for /boot/, an automount
223 unit is used. The mount point will be created if necessary.
224 No configuration is created for mount points that are configured in
226 fstab(5) or when the target directory contains files.
227 When using this generator in conjunction with btrfs file systems, make
229 sure to set the correct default subvolumes on them, using btrfs
230 subvolume set-default.
231 If the system was booted via systemd-stub(7) and the stub reported to
233 userspace that the kernel image was measured to a TPM2 PCR, then any
234 discovered root and /var/ volume identifiers (and volume encryption key
235 in case it is encrypted) will be automatically measured into PCR 15 on
236 activation, via systemd-pcrfs@.service(8).
237 systemd-gpt-auto-generator implements systemd.generator(7).
239
241 systemd-gpt-auto-generator understands the following kernel command
242 line parameters:
243 systemd.gpt_auto, rd.systemd.gpt_auto
245 Those options take an optional boolean argument, and default to
246 yes. The generator is enabled by default, and a false value may be
247 used to disable it (e.g. "systemd.gpt_auto=0").
248 systemd.image_policy=, rd.systemd.image_policy=
250 Takes an image dissection policy string as argument (as per
251 systemd.image-policy(7)), and allows enforcing a policy on
252 dissection and use of the automatically discovered GPT partition
253 table entries.
254 root=, rootfstype=, rootflags=
256 When root= is used with the special value "gpt-auto" (or if the
257 parameter is not used at all), automatic discovery of the root
258 partition based on the GPT partition type is enabled. Any other
259 value disables this logic.
260 The rootfstype= and rootflags= are used to select the file system
262 type and options when the root file system is automatically
263 discovered.
264 rw, ro
266 Mount the root partition read-write or read-only initially.
267 Note that unlike most kernel command line options these settings do
269 not override configuration in the file system, and the file system
270 may be remounted later. See systemd-remount-fs.service(8).
271 systemd.swap=
273 Takes a boolean argument or enables the option if specified without
274 an argument. If disabled, automatic discovery of swap partition(s)
275 based on GPT partition type is disabled. Defaults to enabled.
276
278 systemd(1), systemd.mount(5), systemd.swap(5), systemd-fstab-
279 generator(8), systemd-cryptsetup@.service(8), systemd-
280 pcrfs@.service(8), machine-id(5), cryptsetup(8), fstab(5), btrfs(8)
281
283 1. UEFI Specification
284 https://uefi.org/specifications
285 2. Discoverable Partitions Specification
287 https://uapi-group.org/specifications/specs/discoverable_partitions_specification
288 3. Boot Loader Interface
290 https://systemd.io/BOOT_LOADER_INTERFACE
291 4. Boot Loader Specification
293 https://uapi-group.org/specifications/specs/boot_loader_specification
294systemd 254 SYSTEMD-GPT-AUTO-GENERATOR(8)