linuxexpert-practice-labs/labs/ubuntu-server/1-2-remote-backups/README.md

Ubuntu Server 1.2: Automated remote backups

A backup of /etc to another machine with rsync over SSH, as a user other than root, a nightly systemd timer, and a restore that keeps owners.

Before you start

The peer, at 10.99.0.2 (name peer), is the backup server, s2. It runs its own sshd, and shares this VM's users and files: an account you create here exists there too, and the peer's /srv/backups is this VM's. Reach it with ssh peer; get a shell in its network with sudo ip netns exec lepeer bash.

The lab writes an /etc/motd for task 3; look at its owner and mode with ls -l /etc/motd before you start.

Tasks

1. As root, back up /etc to /srv/backups/s1-etc/ on the peer as a user bkp (not root), using rsync over SSH with a dedicated key, /root/.ssh/backup_key. sudo rsync -avn --delete -M--fake-super -e "ssh -i /root/.ssh/backup_key" /etc/ bkp@peer:/srv/backups/s1-etc/ lists no files to send and ends with (DRY RUN).
2. Run that backup every day at 1:15 am with a systemd timer that catches up after downtime. systemctl list-timers shows your timer with the next run at 01:15 (plus any random delay); sudo systemctl start of the service ends with "Finished" in its journal.
3. Delete /etc/motd, then restore it from the peer. After the restore, ls -l /etc/motd shows the file with its original owner and mode.

Hints

• ssh-keygen -N "" -f /root/.ssh/backup_key; useradd -m, install -d -o bkp -g bkp, ~bkp/.ssh/authorized_keys. Connect once by hand with -o StrictHostKeyChecking=accept-new so the host key is known.
• rsync -a --delete -M--fake-super -e "ssh -i KEY -o BatchMode=yes": the trailing slash on /etc/ matters.
• A Type=oneshot service and a .timer with OnCalendar=, Persistent=true; enable the timer. systemd-analyze calendar, systemctl list-timers, journalctl -u.
• The same rsync the other way, with -M--fake-super.