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.
/usr/lib/systemd/system-generators/systemd-gpt-auto-generator
systemd-gpt-auto-generator is a unit
generator that automatically discovers root,
/home, /srv 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, chapter 5.
It implements the Discoverable
Partitions Specification. Note that this generator has no
effect on non-GPT systems, or where the directories under the
mount points are already non-empty. 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 GUID | Name | Explanation |
|---|---|---|
| 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 (x86-64) | On 64-bit x86 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 (32-bit ARM) | On 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 (64-bit ARM) | On 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 (Itanium/IA-64) | On Itanium 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 | The first home partition on the disk the root partition is located on is mounted to /home. |
| 3b8f8425-20e0-4f3b-907f-1a25a76f98e8 | Server Data Partition | The first server data partition on the disk the root partition is located on is mounted to /srv. |
| 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f | Swap | All swap partitions located on the disk the root partition is located on are enabled. |
| c12a7328-f81f-11d2-ba4b-00a0c93ec93b | EFI System Partition (ESP) | The first ESP located on the disk the root partition is located on is mounted to /boot or /efi, 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 | /, /srv, /home | Partition is mounted read-only |
GPT_FLAG_NO_AUTO | 0x8000000000000000 | /, /srv, /home | Partition is not mounted automatically |
GPT_FLAG_NO_BLOCK_IO_PROTOCOL | 0x0000000000000002 | ESP | Partition is not 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, 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.
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).