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Merge pull request #7567 from azrdev/patch-1
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automated-local.rst: use GPT UUID for consistent udev rule
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ThomasWaldmann committed Jul 10, 2023
2 parents 52db16b + 27bcc0f commit 56dfc6d
Showing 1 changed file with 5 additions and 19 deletions.
24 changes: 5 additions & 19 deletions docs/deployment/automated-local.rst
Original file line number Diff line number Diff line change
Expand Up @@ -29,26 +29,12 @@ Configuring the system
First, create the ``/etc/backups`` directory (as root).
All configuration goes into this directory.

Then, create ``/etc/backups/40-backup.rules`` with the following content (all on one line)::

ACTION=="add", SUBSYSTEM=="bdi", DEVPATH=="/devices/virtual/bdi/*",
TAG+="systemd", ENV{SYSTEMD_WANTS}="automatic-backup.service"

.. topic:: Finding a more precise udev rule
Find out the ID of the partition table of your backup disk (here assumed to be /dev/sdz):
lsblk --fs -o +PTUUID /dev/sdz

If you always connect the drive(s) to the same physical hardware path, e.g. the same
eSATA port, then you can make a more precise udev rule.

Execute ``udevadm monitor`` and connect a drive to the port you intend to use.
You should see a flurry of events, find those regarding the `block` subsystem.
Pick the event whose device path ends in something similar to a device file name,
typically`sdX/sdXY`. Use the event's device path and replace `sdX/sdXY` after the
`/block/` part in the path with a star (\*). For example:
`DEVPATH=="/devices/pci0000:00/0000:00:11.0/ata3/host2/target2:0:0/2:0:0:0/block/*"`.
Then, create ``/etc/backups/40-backup.rules`` with the following content (all on one line)::

Reboot a few times to ensure that the hardware path does not change: on some motherboards
components of it can be random. In these cases you cannot use a more accurate rule,
or need to insert additional stars for matching the path.
ACTION=="add", SUBSYSTEM=="block", ENV{ID_PART_TABLE_UUID}=="<the PTUUID you just noted>", TAG+="systemd", ENV{SYSTEMD_WANTS}="automatic-backup.service"

The "systemd" tag in conjunction with the SYSTEMD_WANTS environment variable has systemd
launch the "automatic-backup" service, which we will create next, as the
Expand Down Expand Up @@ -110,7 +96,7 @@ modify it to suit your needs (e.g. more backup sets, dumping databases etc.).
# Mount file system if not already done. This assumes that if something is already
# mounted at $MOUNTPOINT, it is the backup drive. It won't find the drive if
# it was mounted somewhere else.
(mount | grep $MOUNTPOINT) || mount $partition_path $MOUNTPOINT
findmnt $MOUNTPOINT >/dev/null || mount $partition_path $MOUNTPOINT
drive=$(lsblk --inverse --noheadings --list --paths --output name $partition_path | head --lines 1)
echo "Drive path: $drive"
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