I did use this backup method this weekend on Suse with TAR (GNU) 1.15.1. The documentation how it is in the topicstart is broken for 1.15.1, it will create a corrupt unusable backup.
This is a right command to backup:
tar cvpzf backup.tgz --exclude=/proc --exclude=/lost+found --exclude=/backup.tgz --exclude=/mnt --exclude=/sys /
With the wrong command, TAR1.15.1 ignores the 'exclude' options so it will stop in the sys dir (then your backup is incomplete). In case it doesn't stop it will continue, on the end you get the following error:
tar cvpzf backup.tgz / --exclude=/proc --exclude=/lost+found --exclude=/backup.tgz --exclude=/mnt --exclude=/sys
I'm useing the commands 'time' and 'nice' too now. 'time' tells how long it did take to create the backup, 'nice' sets the CPU proriority on low, so the backup process does not interupt other applications.
tar: --exclude=test1: Cannot stat: No such file or directory
tar: Error exit delayed from previous errors
Perhaps does Ubuntu use another version of TAR where the 'wrong' command will be accepted. Anyway, I think it's wise to warn you to prevent huge troubles.
time nice -n +15 tar cvpzf /backup/290106.tgz --exclude=/proc --exclude=/lost+found --exclude=/backup --exclude=/mnt --exclude=/sys --exclude=/media --exclude=/windows /