So here's something not to do: don't
blindly flail at a system upgrade on
your server!

A couple of nights ago, I decided to
upgrade gopher.visiblink.ca. It runs
Raspberry Pi OS on a Pi Zero W.
Raspberry Pi OS is based on Debian and
the /etc/apt/sources.list file uses
the same codenames as Debian.

So, without going to the Raspberry Pi
OS homepage to check on the latest
version, I just assumed that it was
Debian 12 "Bookworm" and went ahead
with the regular steps toward a
dist-upgrade. It turns out that the
latest version of Raspberry Pi OS is
Debian 11 "Bullseye." Ouch.

Oddly, the system pulled the
"Bookworm" packages and went through
the whole process. But when I
rebooted, I had a broken mess that
wouldn't let me log in.

Fortunately, I had a relatively recent
backup of the important directories
and was able to grab a few more
recently changed files from the SD
card. Even so, reinstalling the OS and
setting everything up again took
several hours.

Lesson learned? I hope so.

On the positive side, the server is up
and running with the latest version of
Raspberry Pi OS and a very lean setup.