x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SYSTEMD-GPT-AUTO-GENERATORsystemd-gpt-auto-generaSYSTEMD-GPT-AUTO-GENERATOR(8)
NAME
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
SYNOPSIS
/usr/lib/systemd/system-generators/systemd-gpt-auto-generator
DESCRIPTION
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 Type | Name | Mount Point | Explanation |
|GUID | | | |
+-------------------------------------+------------------+-----------------+-------------------+
|SD_GPT_ROOT_X86_64 | Root Partition | / | The first |
|4f68bce3-e8cd-4db1-96e7-fbcaf984b709 | (x86-64) | | partition with |
| | | | this type UUID, |
| | | | located on the |
| | | | same disk as the |
| | | | ESP, is used as |
| | | | the root file |
| | | | system / on |
| | | | AMD64 / 64-bit |
| | | | x86 systems. |
+-------------------------------------+------------------+-----------------+-------------------+
|SD_GPT_ROOT_ARM64 | Root Partition | / | The first |
|b921b045-1df0-41c3-af44-4c6f280d3fae | (64-bit ARM) | | partition with |
| | | | this type UUID, |
| | | | located on the |
| | | | same disk as the |
| | | | ESP, is used as |
| | | | the root file |
| | | | system / on |
| | | | AArch64 / 64-bit |
| | | | ARM systems. |
+-------------------------------------+------------------+-----------------+-------------------+
|SD_GPT_ROOT_ALPHA SD_GPT_ROOT_ARC | root partitions | / | The first |
|SD_GPT_ROOT_ARM SD_GPT_ROOT_ARM64 | for other | | partition with |
|SD_GPT_ROOT_IA64 | architectures | | the type UUID |
|SD_GPT_ROOT_LOONGARCH64 | | | matching the |
|SD_GPT_ROOT_MIPS SD_GPT_ROOT_MIPS64 | | | architecture, |
|SD_GPT_ROOT_MIPS_LE | | | located on the |
|SD_GPT_ROOT_MIPS64_LE | | | same disk as the |
|SD_GPT_ROOT_PARISC SD_GPT_ROOT_PPC | | | ESP, is used as |
|SD_GPT_ROOT_PPC64 | | | the root file |
|SD_GPT_ROOT_PPC64_LE | | | system /. For |
|SD_GPT_ROOT_RISCV32 | | | the full list |
|SD_GPT_ROOT_RISCV64 SD_GPT_ROOT_S390 | | | and constant |
|SD_GPT_ROOT_S390X SD_GPT_ROOT_TILEGX | | | values, see |
|SD_GPT_ROOT_X86 SD_GPT_ROOT_X86_64 | | | Discoverable |
|SD_GPT_USR_ALPHA SD_GPT_USR_ARC | | | Partitions |
|SD_GPT_USR_ARM SD_GPT_USR_IA64 | | | Specification[2]. |
|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 | Home Partition | /home/ | The first |
|933ac7e1-2eb4-4f13-b844-0e14e2aef915 | | | partition with |
| | | | this type UUID on |
| | | | the same disk as |
| | | | the ESP is |
| | | | mounted to |
| | | | /home/. |
+-------------------------------------+------------------+-----------------+-------------------+
|SD_GPT_SRV | Server Data | /srv/ | The first |
|3b8f8425-20e0-4f3b-907f-1a25a76f98e8 | Partition | | partition with |
| | | | this type UUID on |
| | | | the same disk as |
| | | | the ESP is |
| | | | mounted to /srv/. |
+-------------------------------------+------------------+-----------------+-------------------+
|SD_GPT_VAR | Variable Data | /var/ | The first |
|4d21b016-b534-45c2-a9fb-5c16e091fd2d | Partition | | partition with |
| | | | this type UUID on |
| | | | the same disk as |
| | | | the ESP 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 | Temporary Data | /var/tmp/ | The first |
|7ec6f557-3bc5-4aca-b293-16ef5df639d1 | Partition | | partition with |
| | | | this type UUID on |
| | | | the same disk as |
| | | | the ESP is |
| | | | mounted to |
| | | | /var/tmp/. |
+-------------------------------------+------------------+-----------------+-------------------+
|SD_GPT_SWAP | Swap | n/a | All partitions |
|0657fd6d-a4ab-43c4-84e5-0933c84b4f4f | | | with this type |
| | | | UUID on the same |
| | | | disk as the ESP |
| | | | are used as swap. |
+-------------------------------------+------------------+-----------------+-------------------+
|SD_GPT_ESP | EFI System | /efi/ or /boot/ | The first |
|c12a7328-f81f-11d2-ba4b-00a0c93ec93b | Partition (ESP) | | partition with |
| | | | this type UUID |
| | | | located on the |
| | | | same disk as the |
| | | | root partition is |
| | | | mounted to /boot/ |
| | | | or /efi/, see |
| | | | below. |
+-------------------------------------+------------------+-----------------+-------------------+
|SD_GPT_XBOOTLDR | Extended Boot | /boot/ | The first |
|bc13c2ff-59e6-4262-a352-b275fd6f7172 | Loader Partition | | partition with |
| | | | 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 | Applicable to | Explanation |
+---------------------------------+-------------------+-------------------+
|SD_GPT_FLAG_READ_ONLY | /, /home/, /srv/, | Partition is |
|0x1000000000000000 | /var/, /var/tmp/, | mounted read-only |
| | Extended Boot | |
| | Loader Partition | |
+---------------------------------+-------------------+-------------------+
|SD_GPT_FLAG_NO_AUTO | /, /home/, /srv/, | Partition is not |
|0x8000000000000000 | /var/, /var/tmp/, | mounted |
| | Extended Boot | automatically |
| | Loader Partition | |
+---------------------------------+-------------------+-------------------+
|SD_GPT_FLAG_NO_BLOCK_IO_PROTOCOL | EFI System | Partition is not |
|0x0000000000000002 | Partition (ESP) | mounted |
| | | 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 systemd-pcrfs@.service(8).
systemd-gpt-auto-generator implements systemd.generator(7).
KERNEL COMMAND LINE
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").
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.
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.
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).
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.
SEE ALSO
systemd(1), systemd.mount(5), systemd.swap(5), systemd-fstab-
generator(8), systemd-cryptsetup@.service(8), systemd-
pcrfs@.service(8), machine-id(5), cryptsetup(8), fstab(5), btrfs(8)
NOTES
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
systemd 254 SYSTEMD-GPT-AUTO-GENERATOR(8)
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