Step-by-Step Guide to Upgrade to Debian 12 from Debian 11
Copy & Paste as below:
sed -i ‘s/bullseye/bookworm/g’ /etc/apt/sources.list
sed -i ‘s/bullseye/bookworm/g’ /etc/apt/sources.list.d/*.list
apt-get update -y && apt-get upgrade –without-new-pkgs -y && apt-get full-upgrade -y
reboot
lsb_release -a