I did this yesterday and thought that others might be interested in the issues that I came across. It wasn’t quite as smooth as the upgrade to Bullseye this time last year but there were no show-stoppers. The main issues were: 1. Interface renaming from eth0 to enX0 (as previously mentioned by Andy). Just remember to update /etc/network/interfaces before you reboot for the first time after the upgrade. If you forget, do it via the console and reboot (or ifup enX0). Don’t forget to update anything else that references eth0 - I forgot to update my ip6tables config and wondered for a minute why there was no IPv6 firewalling… You can, of course, choose to keep using eth0 but I like to move with the times :) 2. mrtg now runs in daemon mode rather than being called regularly via cron. It will ask if you want the cron entry removing as part of the upgrade. In my case, I had set up mrtg a few years ago to use /var/www/mrtg for output and for the config file to be /etc/mrtg.cfg. After yesterday’s upgrade, the new version expects the config file to be at /etc/mrtg/mrtg.cfg and uses /var/www/html/mrtg, so I needed to do some minor Apache httpd reconfiguration. I also had to add "Interval: 5” to mrtg.cfg for it to poll every 5 minutes. 3. Exim - this one was a bit strange. The upgrade to Exim 4.96 failed with "option "message_linelength_limit” unknown” while running the post install script. I use a split config so worked round this by commenting out this setting from both /etc/exim4/conf.d/transport/30_exim4-config_remote_smtp and /etc/exim4/conf.d/transport/30_exim4-config_remote_smtp_smarthost then re-running the upgrade. I don’t know if this is the right way to solve this but it worked for my setup. I think those were the only issues I came across (I have a short memory) but will mention anything else that I remember (or come across). Cheers, Mike