I've started using my second machine occasionally, and discovered a
couple of problems with my 3:30 AM daily backup routine. In the
following my main desktop PC is "dev2" and the "hot backup" is "dev3".

- Yes, I know about not copying over .ssh/

- But I learned "the hard way" to not copy over .Xauthority because
doing so confuses things. Various apps complain about not being able
to find $DISPLAY

- Also for Chromium (and related browsers) do *NOT* simply back up new
and changed files in .config/chromium. Delete files on the target
that have ben deleted on the source. Otherwise Chromium gets very
confused. I've adopted a more heavy-handed approach. In the rsync
script I have...

      --filter='- */.Xauthority' \
      --filter='- */.config' \
      --filter='- */.ssh' \

and afterwards I've added...

#
# Rename current ".config" on remote machine and copy over latest
# version from master
xdate=$( date +%Y%m%d )
xdate=$( date -d "${xdate}"-1day +%Y%m%d )
ssh waltdnes@dev3 mv ".config" ".config${xdate}"
scp -r /home/waltdnes/.config waltdnes@dev3:.config

This creates datestamped backups of .config on the target machine.
After a few days, the command "ls -dlrt .config*" shows...

drwx------ 20 waltdnes users    4096 Sep 21 06:16 .config20251003
drwx------ 21 waltdnes waltdnes 4096 Oct  4 03:36 .config20251004
drwx------ 21 waltdnes waltdnes 4096 Oct  5 03:35 .config20251005
drwx------ 21 waltdnes waltdnes 4096 Oct  6 03:35 .config

--
Walter Dnes <waltdnes@???>
There are 2 types of people in this world
1) Those who can extrapolate from incomplete data