[ThomasWaldmann]

Fixes #9834.

The udev rule in the "Automated backups to a local hard drive" guide matched a single partition table UUID, so only the first backup drive started the automatic-backup service, although run.sh accepts every filesystem UUID listed in backup.disks. The "Adding backup hard drives" section did not mention the udev rule at all.

Changes:

• Match on ENV{ID_FS_UUID} (the filesystem UUID, the same one recorded in backup.disks) instead of the partition table UUID.
• Document one rule line per backup drive, or |-separated UUID alternatives in one line.
• Add the "add a udev rule line + udevadm control --reload" step to "Adding backup hard drives".
• Update the overview and the stale sleep 5 comment in run.sh, which referred to the old, imprecise rule.

🤖 Generated with Claude Code

[ThomasWaldmann]

Tested on Debian 13 (systemd 257) with the rule file + service unit from the guide (stub run.sh that only logs) and three loop-device images (GPT + ext4): A and B registered, C not.

Service runs per attach:

Rules file	A	B	C
one ID_FS_UUID line for A	1	0	0
one line for A, one for B	1	1	0
one line with "A|B"	1	1	0
old rule (ID_PART_TABLE_UUID of A)	1	0	–

The last row reproduces #9834. The new rule fires exactly once per attach, and /dev/disk/by-uuid/<uuid> already exists when the service starts (mounting works).

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