How to backup before a release upgrade from Ubuntu 18.04.5 LTS server?

[Ralf Mardorf]

On Sun, 12 Sep 2021 14:52:20 +0200, Bo Berglund wrote:
>I just have to figure out how to exclude certain directories from the
>backup.
>
>And what happens with stuff that has been symlinked to two places like
>my www dir, will it be copied from both places then making the archive
>twice as big?
>
>And why the need to shut down the server and boot it with installation
>media?

Hi,

tar provides to "exclude" patterns, but IMO those are tricky to use, my
recommendation is not to use an "exclude" pattern, unless you really
know what you are doing.

The good news, tar doesn't follow symlinks, it just backups the symlink
file.

The shutdown is needed, because you cannot lock everything, so if you
backup a running system, you backup a system in different
(probably inconsistent) states. 

The successors of the AT&T UNIX "dump" utility can make a backup of a
file system in progress, if the file system provides to do snapshots.

I'm a litle bit confused, since
http://manpages.ubuntu.com/manpages/bionic/man8/dump.8.html claims
"dump - ext2/3/4 filesystem backup".

https://en.wikipedia.org/wiki/Snapshot_(computer_storage)

Regards,
Ralf