Database backup should be created automatically for you inside the docker container, the path is
shared/backup/db/latest.sql.gz
Regarding upgrades and creating backups, have a look here http://xibo.org.uk/manual/en/install_cms.html#upgrading_xibo
(it’s pretty much whole directory)
Since you’re using Ubuntu, then you can simply follow the instructions under Upgrading in Alex’s guide Xibo 1.8.0 with Docker on Ubuntu 16.04
As for any other software for backups, I’m afraid I don’t have any recommendations, but perhaps someone else from the Xibo community will suggest something.