My backup went from 5.9 GB to 66 MB
Turns out a good backup is as much about what you leave out.
I set up a nightly backup for my home server. Every night at 3 a.m. it bundles up everything important onto a USB drive and keeps the last seven nights.
The first version was 5.9 GB a night. Most of that was stuff the server can rebuild on its own in minutes — like keeping the cardboard box your couch came in, along with the couch.
Once I cut the rebuildable stuff, it dropped to 66 MB. Same protection, a fraction of the space, and fast enough that I'll actually notice if it ever fails.
A root cron job in /etc/cron.d runs a script at 03:00 that tars the agent's home and /srv data to an ext4 USB volume (mounted by UUID in fstab), keeps the 7 newest archives, and logs to /var/log.
Nearly all the bulk was Podman's overlay storage — container image layers. Those are reproducible from the Containerfile, so they're cache, not data. Excluding them cut the archive by about 99%.
tar -czf "$DEST/marvin-backup-$(date +%F-%H%M).tar.gz" \ --exclude=/home/openclaw/.local/share/containers/storage \ /home/openclaw /srv/marvin ls -1t "$DEST"/marvin-backup-*.tar.gz | tail -n +8 | xargs -r rm --
Still on my list: a real restore test, and a copy that doesn't live in the same room. A USB stick next to the server covers a dead disk — not a fire or a break-in.