I wanted to undo all my hacks and wanted to restore the original partition and start all over again.
I didn't like the way I added the C-compiler to my system.
The files didn't have their original dates anymore because I didn't use the -p during the copy process (—preserve attributes).
I did a cp- p /var/lib/current-version /var/lib/current-version.org and changed the text "18.104.22.168" to "22.214.171.124" in /var/lib/current-version.
After that, I did a firmware "upgrade" using the webinterface….
After 15 minutes I could start hacking again.
Isn't this the easiest way to revert to the system firmware?