On: Learn just enough Linux to get things done

[emmelaich]

In about 40 years of using Unix I have never used r or u.

[liveoneggs → emmelaich]

both seem fairly important in the 40-years-ago world concerning the 't'(ape) part of tar but okay.

I use them frequently as an "rsync"-ish into the archive file, which I can then use to take point-in-time snapshot/backups.