Error when tar-backing live linux machine?

Question

linux

I have only one partition on the HDD: sda1, mounted it to /mnt/root , and a network drive on another machine to /mnt/backup , now sudo tar -cvzpf /mnt/backup/ubuntu-sda1.tar.gz /mnt/root . Is it normal for a backup to go through while the system is running, what are the possible incidents, is there recursion?

UPD.
Renamed the question because I see:
tar: Exiting with a failed status due to errors encountered

When using the command:
tar -cvpzf backup.tar.gz --exclude=/backup.tar.gz --exclude=/proc --exclude=/lost+found --exclude=/sys --exclude=/mnt --exclude=/media --exclude=/dev /

What could be the reasons, how to solve?

Answer 1

For backup of whole partitions I would suggest dump/restore

Answer 2

tar --one-file-system will only back up the root partition (without /dev and /proc, of course, but if the installation is scattered over partitions like /usr, /var or /home, as some outdated guides recommend, then you will have to back them up with a separate command) .
And you need to understand that some applications, such as databases, are not recommended to be backed up by regular copying while they are running (and even harmful to the backup).

Answer 3

Did you mount the same FS twice - on / and on /mnt/root? Oh right...