I recently upgrade a couple of machines from Debian Stretch to Debian Bookworm.

The first one was a remote box, which would have meant a reinstall via a Lights Out, reconfigure, and restore if it went wrong (which would have been a monumental pain).

I decided to upgrade from Stretch to Buster to Bullseye to Bookworm, rather than chancing a jump of three versions.

It turns out that it was as simple as changing the distribution name in /etc/apt/sources.list, running apt-get dist-upgrade, and rebooting three times.

The other machine was an old laptop which hadn't been switched on for years.
I followed exactly the same procedure, with the difference that I used it while I was upgrading it.
Again, I changed the distro, apt-get dist-upgraded, and rebooted after each update.

However, while I was in the middle of a dist-upgrade, I accidentally Ctrl C'd in the wrong terminal and stopped the running command. This left the machine in a semi-updated state. I thought this would have totally messed things up, but it wasn't too bad. I had to remove a package that conflicted with another one on the system, and then I restarted the command with the --fix-broken option.
No problems at all.


I'm really impressed with the ease of these updates. Big thanks to the Debian team for their hard work.
I only wish they'd held out against the SystemD-ification of Linux.
Yes, I still don't like it.