Debian 11 has been released so it's time to upgrade. I only have postfix and a web server running on my server so it was pretty easy to make the switch from buster to bullseye. First edit
/etc/apt/sources.list and replace the word buster with bullseye. That includes changing buster-updates to bullseye-updates. The only lines that are different are the http://security.debian.org URLs at the bottom. They need to have bullseye-security instead of buster-updates. After making the changes my sources.list looked like:
deb http://deb.debian.org/debian/ bullseye main deb-src http://deb.debian.org/debian/ bullseye main deb http://deb.debian.org/debian/ bullseye-updates main deb-src http://deb.debian.org/debian/ bullseye-updates main deb http://security.debian.org/debian-security bullseye-security main deb-src http://security.debian.org/debian-security bullseye-security main
Then to do the upgrade just run
# apt update # apt full-upgrade
and once it finishes successfully, reboot and you will be on Debian 11. You can then run
# apt autoremove # apt update # apt upgrade
again to remove the old kernel.
Almost everything was working fine after the upgrade from buster to bullseye, with the exception of PHP. When I visited a PHP page on my web server I was shown the source instead. This is because PHP was upgraded from version 7.3 to 7.4 and the configuration files weren't getting loaded. To fix it, make a symlink from conf-enabled to conf-available and restart apache:
# cd /etc/apache2/conf-enabled/ # ln -sf ../conf-available/php7.4-fpm.conf . # /etc/init.d/apache2 restart
After that my PHP was working again. If you are not using php-fpm then it will probably be different.