I'll respond on the issue of triggering the backup, rather than the
specific backup software itself, because my solution for triggering
is separate from the backup software I use (rdiff-backup).
I trigger (some) backup jobs via systemd units, that are triggered by
the insertion of my removeable backup drive. So, I would suggest that
instead of doing a network backup to your 4T drive on the other side of
your pi, you could attach the drive directly to your Computer when you
want to initiate a backup. This doesn't address your desire to have it
happen in the background, though, because you would still need to
remember (or prompt yourself) to attach the drive. I provide the details
anyway just in case they are interesting.
My "backup-exthdd.service" is what performs the actual backup job:
[Unit]
OnFailure=status-email-user@%n.service blinkstick-fail.service
[email protected]
[email protected]
[Service]
Type=oneshot
ExecStart=/bin/mount /extbackup
ExecStart=<your backup job goes here>
ExecStop=/bin/umount /extbackup
ExecStop=/usr/local/bin/blinkstick --index 1 --limit 10 --set-color green
[Install]
WantedBy=dev-disk-by\x2duuid-e0eed9b6\x2d03f1\x2d41ed\x2d80a4\x2dc7cc4ff013c3.device
(the mount and umount Execs there shouldn't be needed, they should be
addressed by systemd unit dependencies, but in practice they were
necessary when I set this up. This was a while ago and systemd may
perform differently now.)
My external backup disk has an encrypted partition on it. So, the job
above actually depends upon the decrypted partition. The job
"[email protected]" handles that. The skeleton of the
job was written by systemd-cryptsetup-generator automatically, based on
content in /etc/crypttab; I then had to adapt it further. The entirety
of it is:
[Unit]
Description=Cryptography Setup for %I
SourcePath=/etc/crypttab
DefaultDependencies=no
Conflicts=umount.target
BindsTo=dev-mapper-%i.device
IgnoreOnIsolate=true
After=systemd-readahead-collect.service systemd-readahead-replay.service
cryptsetup-pre.target
Before=cryptsetup.target
BindsTo=dev-disk-by\x2duuid-e0eed9b6\x2d03f1\x2d41ed\x2d80a4\x2dc7cc4ff013c3.device
After=dev-disk-by\x2duuid-e0eed9b6\x2d03f1\x2d41ed\x2d80a4\x2dc7cc4ff013c3.device
Before=umount.target
StopWhenUnneeded=true
[Service]
Type=oneshot
RemainAfterExit=yes
TimeoutSec=0
ExecStart=/lib/systemd/systemd-cryptsetup attach 'extbackup'
'/dev/disk/by-uuid/e0eed9b6-03f1-41ed-80a4-c7cc4ff013c3' '/root/exthdd.key'
'luks,noauto'
ExecStop=/lib/systemd/systemd-cryptsetup detach 'extbackup'
So when the remote disk device with the UUID
e0eed9b6-03f1-41ed-80a4-c7cc4ff013c3 appears on the system, its
appearance causes systemd to start the "backup-exthdd.service" job,
which depends upon the bits to enable the encrypted volume.
(the "blinkstick-fail.service" and ExecStop=/usr/local/bin/blinkstick…
line relate to a notification system I have: this is my headless NAS,
and the "blinkstick" is a little multicolour LED attached via USB. In
normal circumstances it is switched off. When a job is running it
changes to a particular colour; when the job finished successfully, it's
green - indicating I can unplug the drive (it's all unmounted etc.), if
anything goes wrong it turns red.)
