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NAME | SYNOPSIS | DESCRIPTION | KERNEL COMMAND LINE | SEE ALSO | NOTES | COLOPHON |
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SYSTEMD-...ENERATOR(8) systemd-gpt-auto-generator SYSTEMD-...ENERATOR(8)
systemd-gpt-auto-generator - Generator for automatically
discovering and mounting root, /home/, /srv/, /var/ and /var/tmp/
partitions, as well as discovering and enabling swap partitions,
based on GPT partition type GUIDs
/usr/lib/systemd/system-generators/systemd-gpt-auto-generator
systemd-gpt-auto-generator is a unit generator that automatically
discovers the root partition, /home/, /srv/, /var/, /var/tmp/,
the EFI System Partition (ESP), the Extended Boot Loader
Partition (XBOOTLDR), and swap partitions and creates mount and
swap units for them, based on the partition type GUIDs of GUID
partition tables (GPT). See UEFI Specification[1], chapter 5 for
more details. It implements the Discoverable Partitions
Specification[2].
Note that this generator has no effect on non-GPT systems. It
will also not create mount point configuration for directories
which already contain files or if the mount point is explicitly
configured in fstab(5). Additionally no unit will be created for
the ESP or the XBOOTLDR partition if mount entries are found in
the /boot/ or /efi/ hierarchies in fstab(5).
If the units this generator creates are overridden, for example
by units in directories with higher precedence, drop-ins and
additional dependencies created by this generator might still be
used.
This generator will only look for the root partition on the same
physical disk where the EFI System Partition (ESP) is located.
Note that support from the boot loader is required: the EFI
variable LoaderDevicePartUUID of the
4a67b082-0a4c-41cf-b6c7-440b29bb8c4f vendor UUID is used to
determine from which partition, and hence the disk, from which
the system was booted. If the boot loader does not set this
variable, this generator will not be able to detect the root
partition. See the Boot Loader Interface[3] for details.
Similarly, this generator will only look for the other partitions
on the same physical disk as the root partition. In this case,
boot loader support is not required. These partitions will not be
searched for on systems where the root file system is distributed
on multiple disks, for example via btrfs RAID.
systemd-gpt-auto-generator is useful for centralizing file system
configuration in the partition table and making configuration in
/etc/fstab or on the kernel command line unnecessary.
This generator looks for the partitions based on their partition
type GUID. The following partition type GUIDs are identified:
Table 1. Partition Type GUIDs
┌─────────────────────────┬──────────────────────────────────────┬───────────────┬─────────────┬───────────────────┐
│ Partition │ GUID │ Name │ Mount Point │ Explanation │
│ Type │ │ │ │ │
├─────────────────────────┼──────────────────────────────────────┼───────────────┼─────────────┼───────────────────┤
│ SD_GPT_ROOT_X86_64 │ 4f68bce3-e8cd-4db1-96e7-fbcaf984b709 │ Root │ / │ The first │
│ │ │ Partition │ │ partition │
│ │ │ (x86-64) │ │ with this │
│ │ │ │ │ type UUID, │
│ │ │ │ │ located on │
│ │ │ │ │ the same │
│ │ │ │ │ disk as the │
│ │ │ │ │ ESP used for │
│ │ │ │ │ booting, is │
│ │ │ │ │ used as the │
│ │ │ │ │ root file │
│ │ │ │ │ system / on │
│ │ │ │ │ AMD64 / │
│ │ │ │ │ 64-bit x86 │
│ │ │ │ │ systems. │
├─────────────────────────┼──────────────────────────────────────┼───────────────┼─────────────┼───────────────────┤
│ SD_GPT_ROOT_ARM64 │ b921b045-1df0-41c3-af44-4c6f280d3fae │ Root │ / │ The first │
│ │ │ Partition │ │ partition │
│ │ │ (64-bit ARM) │ │ with this │
│ │ │ │ │ type UUID, │
│ │ │ │ │ located on │
│ │ │ │ │ the same │
│ │ │ │ │ disk as the │
│ │ │ │ │ ESP used for │
│ │ │ │ │ booting, is │
│ │ │ │ │ used as the │
│ │ │ │ │ root file │
│ │ │ │ │ system / on │
│ │ │ │ │ AArch64 / │
│ │ │ │ │ 64-bit ARM │
│ │ │ │ │ systems. │
├─────────────────────────┼──────────────────────────────────────┼───────────────┼─────────────┼───────────────────┤
│ SD_GPT_ROOT_ALPHA │ ... │ Root │ / │ The first │
│ SD_GPT_ROOT_ARC │ │ partitions │ │ partition │
│ SD_GPT_ROOT_ARM │ │ for other │ │ with the │
│ SD_GPT_ROOT_ARM64 │ │ architectures │ │ type UUID │
│ SD_GPT_ROOT_IA64 │ │ │ │ matching the │
│ SD_GPT_ROOT_LOONGARCH64 │ │ │ │ architecture, │
│ SD_GPT_ROOT_MIPS │ │ │ │ located on │
│ SD_GPT_ROOT_MIPS64 │ │ │ │ the same │
│ SD_GPT_ROOT_MIPS_LE │ │ │ │ disk as the │
│ SD_GPT_ROOT_MIPS64_LE │ │ │ │ ESP used for │
│ SD_GPT_ROOT_PARISC │ │ │ │ booting, is │
│ SD_GPT_ROOT_PPC │ │ │ │ used as the │
│ SD_GPT_ROOT_PPC64 │ │ │ │ root file │
│ SD_GPT_ROOT_PPC64_LE │ │ │ │ system /. │
│ SD_GPT_ROOT_RISCV32 │ │ │ │ For the full │
│ SD_GPT_ROOT_RISCV64 │ │ │ │ list and │
│ SD_GPT_ROOT_S390 │ │ │ │ constant │
│ SD_GPT_ROOT_S390X │ │ │ │ values, see │
│ SD_GPT_ROOT_TILEGX │ │ │ │ Discoverable │
│ SD_GPT_ROOT_X86 │ │ │ │ Partitions │
│ SD_GPT_ROOT_X86_64 │ │ │ │ Specification[2]. │
│ SD_GPT_USR_ALPHA │ │ │ │ │
│ SD_GPT_USR_ARC │ │ │ │ │
│ SD_GPT_USR_ARM │ │ │ │ │
│ SD_GPT_USR_IA64 │ │ │ │ │
│ SD_GPT_USR_LOONGARCH64 │ │ │ │ │
│ SD_GPT_USR_MIPS_LE │ │ │ │ │
│ SD_GPT_USR_MIPS64_LE │ │ │ │ │
│ SD_GPT_USR_PARISC │ │ │ │ │
│ SD_GPT_USR_PPC │ │ │ │ │
│ SD_GPT_USR_PPC64 │ │ │ │ │
│ SD_GPT_USR_PPC64_LE │ │ │ │ │
│ SD_GPT_USR_RISCV32 │ │ │ │ │
│ SD_GPT_USR_RISCV64 │ │ │ │ │
│ SD_GPT_USR_S390 │ │ │ │ │
│ SD_GPT_USR_S390X │ │ │ │ │
│ SD_GPT_USR_TILEGX │ │ │ │ │
│ SD_GPT_USR_X86 │ │ │ │ │
├─────────────────────────┼──────────────────────────────────────┼───────────────┼─────────────┼───────────────────┤
│ SD_GPT_HOME │ 933ac7e1-2eb4-4f13-b844-0e14e2aef915 │ Home │ /home/ │ The first │
│ │ │ Partition │ │ partition with │
│ │ │ │ │ this type UUID on │
│ │ │ │ │ the same disk as │
│ │ │ │ │ the root │
│ │ │ │ │ partition is │
│ │ │ │ │ mounted to │
│ │ │ │ │ /home/. │
├─────────────────────────┼──────────────────────────────────────┼───────────────┼─────────────┼───────────────────┤
│ SD_GPT_SRV │ 3b8f8425-20e0-4f3b-907f-1a25a76f98e8 │ Server Data │ /srv/ │ The first │
│ │ │ Partition │ │ partition with │
│ │ │ │ │ this type UUID on │
│ │ │ │ │ the same disk as │
│ │ │ │ │ the root │
│ │ │ │ │ partition is │
│ │ │ │ │ mounted to /srv/. │
├─────────────────────────┼──────────────────────────────────────┼───────────────┼─────────────┼───────────────────┤
│ SD_GPT_VAR │ 4d21b016-b534-45c2-a9fb-5c16e091fd2d │ Variable Data │ /var/ │ The first │
│ │ │ Partition │ │ partition with │
│ │ │ │ │ this type UUID on │
│ │ │ │ │ the same disk as │
│ │ │ │ │ the root │
│ │ │ │ │ partition is │
│ │ │ │ │ mounted to /var/ │
│ │ │ │ │ — under the │
│ │ │ │ │ condition its │
│ │ │ │ │ partition UUID │
│ │ │ │ │ matches the first │
│ │ │ │ │ 128 bit of the │
│ │ │ │ │ HMAC-SHA256 of │
│ │ │ │ │ the GPT type uuid │
│ │ │ │ │ of this partition │
│ │ │ │ │ keyed by the │
│ │ │ │ │ machine ID of the │
│ │ │ │ │ installation │
│ │ │ │ │ stored in │
│ │ │ │ │ machine-id(5). │
├─────────────────────────┼──────────────────────────────────────┼───────────────┼─────────────┼───────────────────┤
│ SD_GPT_TMP │ 7ec6f557-3bc5-4aca-b293-16ef5df639d1 │ Temporary │ /var/tmp/ │ The first │
│ │ │ Data │ │ partition with │
│ │ │ Partition │ │ this type UUID on │
│ │ │ │ │ the same disk as │
│ │ │ │ │ the root │
│ │ │ │ │ partition is │
│ │ │ │ │ mounted to │
│ │ │ │ │ /var/tmp/. │
├─────────────────────────┼──────────────────────────────────────┼───────────────┼─────────────┼───────────────────┤
│ SD_GPT_SWAP │ 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f │ Swap │ n/a │ All partitions │
│ │ │ │ │ with this type │
│ │ │ │ │ UUID on the same │
│ │ │ │ │ disk as the root │
│ │ │ │ │ partition are │
│ │ │ │ │ used as swap. │
├─────────────────────────┼──────────────────────────────────────┼───────────────┼─────────────┼───────────────────┤
│ SD_GPT_ESP │ c12a7328-f81f-11d2-ba4b-00a0c93ec93b │ EFI System │ /efi/ or │ The first │
│ │ │ Partition │ /boot/ │ partition with │
│ │ │ (ESP) │ │ this type UUID │
│ │ │ │ │ located on the │
│ │ │ │ │ same disk as the │
│ │ │ │ │ root partition is │
│ │ │ │ │ mounted to /boot/ │
│ │ │ │ │ or /efi/, see │
│ │ │ │ │ below. │
├─────────────────────────┼──────────────────────────────────────┼───────────────┼─────────────┼───────────────────┤
│ SD_GPT_XBOOTLDR │ bc13c2ff-59e6-4262-a352-b275fd6f7172 │ Extended Boot │ /boot/ │ The first │
│ │ │ Loader │ │ partition with │
│ │ │ Partition │ │ this type UUID │
│ │ │ │ │ located on the │
│ │ │ │ │ same disk as the │
│ │ │ │ │ root partition is │
│ │ │ │ │ mounted to │
│ │ │ │ │ /boot/, see │
│ │ │ │ │ below. │
└─────────────────────────┴──────────────────────────────────────┴───────────────┴─────────────┴───────────────────┘
This generator understands the following attribute flags for
partitions:
Table 2. Partition Attribute Flags
┌──────────────────────────────────┬────────────────────┬───────────────┬───────────────┐
│ Flag │ Value │ Applicable to │ Explanation │
├──────────────────────────────────┼────────────────────┼───────────────┼───────────────┤
│ SD_GPT_FLAG_READ_ONLY │ 0x1000000000000000 │ /, /home/, │ Partition is │
│ │ │ /srv/, /var/, │ mounted │
│ │ │ /var/tmp/, │ read-only │
│ │ │ Extended Boot │ │
│ │ │ Loader │ │
│ │ │ Partition │ │
├──────────────────────────────────┼────────────────────┼───────────────┼───────────────┤
│ SD_GPT_FLAG_NO_AUTO │ 0x8000000000000000 │ /, /home/, │ Partition is │
│ │ │ /srv/, /var/, │ not mounted │
│ │ │ /var/tmp/, │ automatically │
│ │ │ Extended Boot │ │
│ │ │ Loader │ │
│ │ │ Partition │ │
├──────────────────────────────────┼────────────────────┼───────────────┼───────────────┤
│ SD_GPT_FLAG_NO_BLOCK_IO_PROTOCOL │ 0x0000000000000002 │ EFI System │ Partition is │
│ │ │ Partition │ not mounted │
│ │ │ (ESP) │ automatically │
└──────────────────────────────────┴────────────────────┴───────────────┴───────────────┘
The /home/, /srv/, /var/, /var/tmp/ and swap partitions may be
encrypted in LUKS format. In this case, a device mapper device is
set up under the names /dev/mapper/home, /dev/mapper/srv,
/dev/mapper/var, /dev/mapper/tmp or /dev/mapper/swap. Note that
this might create conflicts if the same partition is listed in
/etc/crypttab with a different device mapper device name.
When systemd is running in the initrd the / partition may be
encrypted with LUKS as well. In this case, a device mapper device
is set up under the name /dev/mapper/root, and a sysroot.mount is
set up that mounts the device under /sysroot. For more
information, see bootup(7).
The root partition can be specified by symlinking
/run/systemd/volatile-root to /dev/block/$major:$minor. This is
especially useful if the root mount has been replaced by some
form of volatile file system (overlayfs).
Mount and automount units for the EFI System Partition (ESP) and
Extended Boot Loader Partition (XBOOTLDR) are generated on EFI
systems. If the disk contains an XBOOTLDR partition, as defined
in the Boot Loader Specification[4], it is made available at
/boot/. This generator creates an automount unit; the mount will
only be activated on-demand when accessed. The mount point will
be created if necessary.
The ESP is mounted to /boot/ if that directory exists and is not
used for XBOOTLDR, and otherwise to /efi/. Same as for /boot/, an
automount unit is used. The mount point will be created if
necessary.
No configuration is created for mount points that are configured
in fstab(5) or when the target directory contains files.
When using this generator in conjunction with btrfs file systems,
make sure to set the correct default subvolumes on them, using
btrfs subvolume set-default.
If the system was booted via systemd-stub(7) and the stub
reported to userspace that the kernel image was measured to a
TPM2 PCR, then any discovered root and /var/ volume identifiers
(and volume encryption key in case it is encrypted) will be
automatically measured into PCR 15 on activation, via
[email protected](8).
systemd-gpt-auto-generator implements systemd.generator(7).
systemd-gpt-auto-generator understands the following kernel
command line parameters:
systemd.gpt_auto, rd.systemd.gpt_auto
Those options take an optional boolean argument, and default
to yes. The generator is enabled by default, and a false
value may be used to disable it (e.g. "systemd.gpt_auto=0").
Added in version 242.
systemd.image_policy=, rd.systemd.image_policy=
Takes an image dissection policy string as argument (as per
systemd.image-policy(7)), and allows enforcing a policy on
dissection and use of the automatically discovered GPT
partition table entries.
Added in version 254.
root=, rootfstype=, rootflags=
When root= is used with the special value "gpt-auto" (or if
the parameter is not used at all), automatic discovery of the
root partition based on the GPT partition type is enabled.
Any other value disables this logic.
The rootfstype= and rootflags= are used to select the file
system type and options when the root file system is
automatically discovered.
Added in version 242.
rw, ro
Mount the root partition read-write or read-only initially.
Note that unlike most kernel command line options these
settings do not override configuration in the file system,
and the file system may be remounted later. See
systemd-remount-fs.service(8).
Added in version 242.
systemd.swap=
Takes a boolean argument or enables the option if specified
without an argument. If disabled, automatic discovery of swap
partition(s) based on GPT partition type is disabled.
Defaults to enabled.
Added in version 254.
systemd(1), systemd.mount(5), systemd.swap(5),
systemd-fstab-generator(8), [email protected](8),
[email protected](8), machine-id(5), cryptsetup(8),
fstab(5), btrfs(8)
1. UEFI Specification
https://uefi.org/specifications
2. Discoverable Partitions Specification
https://uapi-group.org/specifications/specs/discoverable_partitions_specification
3. Boot Loader Interface
https://systemd.io/BOOT_LOADER_INTERFACE
4. Boot Loader Specification
https://uapi-group.org/specifications/specs/boot_loader_specification
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have
a bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 257~devel SYSTEMD-...ENERATOR(8)
Pages that refer to this page: repart.d(5), systemd.mount(5), sysupdate.d(5), file-hierarchy(7), kernel-command-line(7), systemd-boot(7), systemd.directives(7), systemd.generator(7), systemd.image-policy(7), systemd.index(7), systemd-stub(7), systemd-fstab-generator(8), systemd-pcrphase.service(8), systemd-remount-fs.service(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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