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SYSTEMD-GPT-AUTO-GENERATOR(8)        systemd-gpt-auto-generator        SYSTEMD-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
       /lib/systemd/system-generators/systemd-gpt-auto-generator

DESCRIPTION
       systemd-gpt-auto-generator is a unit generator that automatically discovers root, /home/,
       /srv/, /var/, /var/tmp/, the EFI System Partition, the Extended Boot Loader Partition 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. It implements the
       Discoverable Partitions Specification[2]. Note that this generator has no effect on non-GPT
       systems, and on specific mount points that are directories already containing files. Also, on
       systems where the units are explicitly configured (for example, listed in fstab(5)), the
       units this generator creates are overridden, but additional implicit dependencies might be
       created.

       This generator will only look for the root partition on the same physical disk the EFI System
       Partition (ESP) is located on. 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 autodetect 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 GUIDNameMount PointExplanation          │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │44479540-f297-41b2-9af7-d131d5f0458a │ Root Partition (x86) │ /               │ 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 /.         │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │4f68bce3-e8cd-4db1-96e7-fbcaf984b709 │ Root Partition       │ /               │ On 64-bit x86        │
       │                                     │ (x86-64)             │                 │ systems, the first   │
       │                                     │                      │                 │ x86-64 root          │
       │                                     │                      │                 │ partition on the     │
       │                                     │                      │                 │ disk the EFI ESP is  │
       │                                     │                      │                 │ located on is        │
       │                                     │                      │                 │ mounted to the root  │
       │                                     │                      │                 │ directory /.         │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │69dad710-2ce4-4e3c-b16c-21a1d49abed3 │ Root Partition       │ /               │ On 32-bit ARM        │
       │                                     │ (32-bit ARM)         │                 │ systems, the first   │
       │                                     │                      │                 │ ARM root partition   │
       │                                     │                      │                 │ on the disk the EFI  │
       │                                     │                      │                 │ ESP is located on is │
       │                                     │                      │                 │ mounted to the root  │
       │                                     │                      │                 │ directory /.         │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │b921b045-1df0-41c3-af44-4c6f280d3fae │ Root Partition       │ /               │ On 64-bit ARM        │
       │                                     │ (64-bit ARM)         │                 │ systems, the first   │
       │                                     │                      │                 │ ARM root partition   │
       │                                     │                      │                 │ on the disk the EFI  │
       │                                     │                      │                 │ ESP is located on is │
       │                                     │                      │                 │ mounted to the root  │
       │                                     │                      │                 │ directory /.         │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │993d8d3d-f80e-4225-855a-9daf8ed7ea97 │ Root Partition       │ /               │ On Itanium systems,  │
       │                                     │ (Itanium/IA-64)      │                 │ the first Itanium    │
       │                                     │                      │                 │ root partition on    │
       │                                     │                      │                 │ the disk the EFI ESP │
       │                                     │                      │                 │ is located on is     │
       │                                     │                      │                 │ mounted to the root  │
       │                                     │                      │                 │ directory /.         │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │60d5a7fe-8e7d-435c-b714-3dd8162144e1 │ Root Partition       │ /               │ On RISC-V 32-bit     │
       │                                     │ (RISCV-V 32)         │                 │ systems, the first   │
       │                                     │                      │                 │ RISCV-V 32-bit root  │
       │                                     │                      │                 │ partition on the     │
       │                                     │                      │                 │ disk the EFI ESP is  │
       │                                     │                      │                 │ located on is        │
       │                                     │                      │                 │ mounted to the root  │
       │                                     │                      │                 │ directory /.         │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │72ec70a6-cf74-40e6-bd49-4bda08e8f224 │ Root Partition       │ /               │ On RISC-V 64-bit     │
       │                                     │ (RISCV-V 64)         │                 │ systems, the first   │
       │                                     │                      │                 │ RISCV-V 64-bit root  │
       │                                     │                      │                 │ partition on the     │
       │                                     │                      │                 │ disk the EFI ESP is  │
       │                                     │                      │                 │ located on is        │
       │                                     │                      │                 │ mounted to the root  │
       │                                     │                      │                 │ directory /.         │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │933ac7e1-2eb4-4f13-b844-0e14e2aef915 │ Home Partition       │ /home/          │ The first home       │
       │                                     │                      │                 │ partition on the     │
       │                                     │                      │                 │ disk the root        │
       │                                     │                      │                 │ partition is located │
       │                                     │                      │                 │ on is mounted to     │
       │                                     │                      │                 │ /home/.              │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │3b8f8425-20e0-4f3b-907f-1a25a76f98e8 │ Server Data          │ /srv/           │ The first server     │
       │                                     │ Partition            │                 │ data partition on    │
       │                                     │                      │                 │ the disk the root    │
       │                                     │                      │                 │ partition is located │
       │                                     │                      │                 │ on is mounted to     │
       │                                     │                      │                 │ /srv/.               │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │4d21b016-b534-45c2-a9fb-5c16e091fd2d │ Variable Data        │ /var/           │ The first variable   │
       │                                     │ Partition            │                 │ data partition on    │
       │                                     │                      │                 │ the disk the root    │
       │                                     │                      │                 │ partition is located │
       │                                     │                      │                 │ on 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).               │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │7ec6f557-3bc5-4aca-b293-16ef5df639d1 │ Temporary Data       │ /var/tmp/       │ The first temporary  │
       │                                     │ Partition            │                 │ data partition on    │
       │                                     │                      │                 │ the disk the root    │
       │                                     │                      │                 │ partition is located │
       │                                     │                      │                 │ on is mounted to     │
       │                                     │                      │                 │ /var/tmp/.           │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │0657fd6d-a4ab-43c4-84e5-0933c84b4f4f │ Swap                 │ n/a             │ All swap partitions  │
       │                                     │                      │                 │ located on the disk  │
       │                                     │                      │                 │ the root partition   │
       │                                     │                      │                 │ is located on are    │
       │                                     │                      │                 │ enabled.             │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │c12a7328-f81f-11d2-ba4b-00a0c93ec93b │ EFI System Partition │ /efi/ or /boot/ │ The first ESP        │
       │                                     │ (ESP)                │                 │ located on the disk  │
       │                                     │                      │                 │ the root partition   │
       │                                     │                      │                 │ is located on is     │
       │                                     │                      │                 │ mounted to /boot/ or │
       │                                     │                      │                 │ /efi/, see below.    │
       ├─────────────────────────────────────┼──────────────────────┼─────────────────┼──────────────────────┤
       │bc13c2ff-59e6-4262-a352-b275fd6f7172 │ Extended Boot Loader │ /boot/          │ The first Extended   │
       │                                     │ Partition            │                 │ Boot Loader          │
       │                                     │                      │                 │ Partition is mounted │
       │                                     │                      │                 │ to /boot/, see       │
       │                                     │                      │                 │ below.               │
       └─────────────────────────────────────┴──────────────────────┴─────────────────┴──────────────────────┘

       This generator understands the following attribute flags for partitions:

       Table 2. Partition Attributes
       ┌──────────────────────────────┬────────────────────┬──────────────────────┬──────────────────────┐
       │NameValueApplicable toExplanation          │
       ├──────────────────────────────┼────────────────────┼──────────────────────┼──────────────────────┤
       │GPT_FLAG_READ_ONLY            │ 0x1000000000000000 │ /, /home/, /srv/,    │ Partition is mounted │
       │                              │                    │ /var/, /var/tmp/,    │ read-only            │
       │                              │                    │ Extended Boot Loader │                      │
       │                              │                    │ Partition            │                      │
       ├──────────────────────────────┼────────────────────┼──────────────────────┼──────────────────────┤
       │GPT_FLAG_NO_AUTO              │ 0x8000000000000000 │ /, /home/, /srv/,    │ Partition is not     │
       │                              │                    │ /var/, /var/tmp/,    │ mounted              │
       │                              │                    │ Extended Boot Loader │ automatically        │
       │                              │                    │ Partition            │                      │
       ├──────────────────────────────┼────────────────────┼──────────────────────┼──────────────────────┤
       │GPT_FLAG_NO_BLOCK_IO_PROTOCOL │ 0x0000000000000002 │ EFI System Partition │ Partition is not     │
       │                              │                    │ (ESP)                │ mounted              │
       │                              │                    │                      │ automatically        │
       └──────────────────────────────┴────────────────────┴──────────────────────┴──────────────────────┘

       The /home/, /srv/, /var/ and /var/tmp/ 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 and /dev/mapper/tmp. 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 in LUKS format 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).

       Mount and automount units for the EFI System Partition (ESP) are generated on EFI systems.
       The ESP is mounted to /boot/ (except if an Extended Boot Loader partition exists, see below),
       unless a mount point directory /efi/ exists, in which case it is mounted there. Since this
       generator creates an automount unit, the mount will only be activated on-demand, when
       accessed. On systems where /boot/ (or /efi/ if it exists) is an explicitly configured mount
       (for example, listed in fstab(5)) or where the /boot/ (or /efi/) mount point is non-empty, no
       mount units are generated.

       If the disk contains an Extended Boot Loader partition, as defined in the Boot Loader
       Specification[4], it is made available at /boot/ (by means of an automount point, similar to
       the ESP, see above). If both an EFI System Partition and an Extended Boot Loader partition
       exist the latter is preferably mounted to /boot/. Make sure to create both /efi/ and /boot/
       to ensure both partitions are mounted.

       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.

       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 negative value may be used to disable it.

       root=
           When used with the special value "gpt-auto", automatic discovery of the root partition
           based on the GPT partition type is enabled. Any other value disables this generator.

       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).

SEE ALSO
       systemd(1), systemd.mount(5), systemd.swap(5), systemd-fstab-generator(8), systemd-
       cryptsetup@.service(8), machine-id(5), cryptsetup(8), fstab(5), btrfs(8)

NOTES
        1. UEFI Specification
           https://uefi.org/specifications

        2. Discoverable Partitions Specification
           https://systemd.io/DISCOVERABLE_PARTITIONS

        3. Boot Loader Interface
           https://systemd.io/BOOT_LOADER_INTERFACE

        4. Boot Loader Specification
           https://systemd.io/BOOT_LOADER_SPECIFICATION



systemd 249                                                            SYSTEMD-GPT-AUTO-GENERATOR(8)
systemd-gpt-auto-generator(8)
NAME SYNOPSIS DESCRIPTION
Table 1. Partition Type GUIDs Table 2. Partition Attributes
KERNEL COMMAND LINE SEE ALSO NOTES

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