Good old rsync. Very handy for backing up and entire system to another. It only transfers files that have changed too.
rsync -av -e ssh --delete --exclude /tmp --exclude /chroots --exclude /sys --exclude /proc / user@destination::backups/folder
Uses ssh to connect, deletes backed up files that are no longer on the source and excludes a few unnecessary folders. If you have setup .ssh/authorized_keys you wont even need a password.
What’s even more helpful is that if you have a firewall that restricts traffic to port 22/tcp coming from the source you can use it in reverse and pull the backup from the source to the destination
rsync -av -e ssh --exclude /sys --exclude /proc user@source:/ ./destination_folder
Add to this that if you have a key file you like to use for ssh to identify you by enclosing the ssh call in single quotes.:
rsync -av -e 'ssh -i file.key' --exclude /sys --exclude /proc user@source:/ ./destination_folder