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docs: document the partition UUID used by homed

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Zbigniew Jędrzejewski-Szmek 2021-11-18 15:16:20 +01:00
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1
docs/DISCOVERABLE_PARTITIONS.md
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@ -158,6 +158,7 @@ Interface](https://systemd.io/BOOT_LOADER_INTERFACE).
| _Server Data Partition_ | `3b8f8425-20e0-4f3b-907f-1a25a76f98e8` | Any native, optionally in LUKS | The first partition with this type UUID on the disk containing the root partition is automatically mounted to `/srv/`. If the partition is encrypted with LUKS, the device mapper file will be named `/dev/mapper/srv`. |
| _Variable Data Partition_ | `4d21b016-b534-45c2-a9fb-5c16e091fd2d` | Any native, optionally in LUKS | The first partition with this type UUID on the disk containing the root partition is automatically mounted to `/var/` — under the condition that its partition UUID matches the first 128 bits of `HMAC-SHA256(machine-id, 0x4d21b016b53445c2a9fb5c16e091fd2d)` (i.e. the SHA256 HMAC hash of the binary type UUID keyed by the machine ID as read from [`/etc/machine-id`](https://www.freedesktop.org/software/systemd/man/machine-id.html). This special requirement is made because `/var/` (unlike the other partition types listed here) is inherently private to a specific installation and cannot possibly be shared between multiple OS installations on the same disk, and thus should be bound to a specific instance of the OS, identified by its machine ID. If the partition is encrypted with LUKS, the device mapper file will be named `/dev/mapper/var`. |
| _Temporary Data Partition_ | `7ec6f557-3bc5-4aca-b293-16ef5df639d1` | Any native, optionally in LUKS | The first partition with this type UUID on the disk containing the root partition is automatically mounted to `/var/tmp/`. If the partition is encrypted with LUKS, the device mapper file will be named `/dev/mapper/tmp`. Note that the intended mount point is indeed `/var/tmp/`, not `/tmp/`. The latter is typically maintained in memory via <tt>tmpfs</tt> and does not require a partition on disk. In some cases it might be desirable to make `/tmp/` persistent too, in which case it is recommended to make it a symlink or bind mount to `/var/tmp/`, thus not requiring its own partition type UUID. |
| _Per-user Home Partition_ | `773f91ef-66d4-49b5-bd83-d683bf40ad16` | Any native, optionally in LUKS | A home partition of a user, managed by [`systemd-homed`](https://www.freedesktop.org/software/systemd/man/systemd-homed.html). |
| _Generic Linux Data Partition_ | `0fc63daf-8483-4772-8e79-3d69d8477de4` | Any native, optionally in LUKS | No automatic mounting takes place for other Linux data partitions. This partition type should be used for all partitions that carry Linux file systems. The installer needs to mount them explicitly via entries in <tt>/etc/fstab</tt>. Optionally, these partitions may be encrypted with LUKS. This partition type predates the Discoverable Partitions Specification. |
Other GPT type IDs might be used on Linux, for example to mark software RAID or

5
tools/list-discoverable-partitions.py
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@ -46,6 +46,7 @@ TYPES = {
'TMP': 'Temporary Data Partition',
'SWAP': 'Swap',
'HOME': 'Home Partition',
'USER_HOME': 'Per-user Home Partition',
'LINUX_GENERIC': 'Generic Linux Data Partition',
'XBOOTLDR': 'Extended Boot Loader Partition',
}
@ -126,6 +127,10 @@ DESCRIPTIONS = {
'<tt>tmpfs</tt> and does not require a partition on disk. In some cases it might be '
'desirable to make `/tmp/` persistent too, in which case it is recommended to make it '
'a symlink or bind mount to `/var/tmp/`, thus not requiring its own partition type UUID.'),
'USER_HOME': (
'Any native, optionally in LUKS',
'A home partition of a user, managed by '
'[`systemd-homed`](https://www.freedesktop.org/software/systemd/man/systemd-homed.html).'),
'LINUX_GENERIC': (
'Any native, optionally in LUKS',
'No automatic mounting takes place for other Linux data partitions. This partition type '