systemd-gpt-auto-generator

SYSTEMD-GPT-AUTO-GENERATORsystemd-gpt-auto-generaSYSTEMD-GPT-AUTO-GENERATOR(8)



NAME
       systemd-gpt-auto-generator - Generator for automatically discovering
       and mounting root, /home and /srv 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 root, /home/, /srv/, 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 root partitions on the same physical
       disk the EFI System Partition (ESP) is located on. It will only look
       for the other partitions on the same physical disk the root file system
       is located on. 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 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                                 │                  │                 │                  │
       ├─────────────────────────────────────┼──────────────────┼─────────────────┼──────────────────┤
       │44479540-f297-41b2-9af7-d131d5f0458a │ Root Partition   │ /               │ On 32-bit x86    │
       │                                     │ (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       │
       │                                     │ (Itanium/IA-64)  │                 │ systems, the     │
       │                                     │                  │                 │ first Itanium    │
       │                                     │                  │                 │ 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. │
       ├─────────────────────────────────────┼──────────────────┼─────────────────┼──────────────────┤
       │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       │ /efi/ or /boot/ │ The first ESP    │
       │                                     │ Partition (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    │ /boot/          │ The first        │
       │                                     │ Loader Partition │                 │ Extended Boot    │
       │                                     │                  │                 │ Loader Partition │
       │                                     │                  │                 │ is mounted to    │
       │                                     │                  │                 │ /boot, see       │
       │                                     │                  │                 │ below.           │
       └─────────────────────────────────────┴──────────────────┴─────────────────┴──────────────────┘

       This generator understands the following attribute flags for
       partitions:

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

       The /home/ and /srv/ partitions may be encrypted in LUKS format. In
       this case, a device mapper device is set up under the names
       /dev/mapper/home and /dev/mapper/srv. Note that this might create
       conflicts if the same partition is listed in /etc/crypttab with a
       different device mapper device name.

       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[3], 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), cryptsetup(8), fstab(5),
       btrfs(8)

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

        2. Discoverable Partitions Specification
           https://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/

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



systemd 242                                      SYSTEMD-GPT-AUTO-GENERATOR(8)