wget https://ftp-master.debian.org/keys/archive-key-11.asc gpg --import archive-key-11.asc Then verify:
deb http://archive.debian.org/debian/ bullseye main contrib non-free deb http://archive.debian.org/debian-security bullseye-security main For most users installing Debian 11 today : → firmware-11.11.0-amd64-netinst.iso from the unofficial non-free archive. iso debian 11
sha256sum -c SHA256SUMS --ignore-missing Import the Debian signing key: wget https://ftp-master
sudo sed -i 's/buster/bullseye/g' /etc/apt/sources.list sudo apt update sudo apt upgrade --without-new-pkgs sudo apt full-upgrade sudo apt autoremove sudo reboot But you’ll need the for a clean install. 10. Security status (as of 2025) Debian 11 is oldstable (Debian 12 = stable, 13 = testing). Security support via the oldstable suite ends ~August 2026 . After that, use archive.debian.org repositories. Security status (as of 2025) Debian 11 is
Update /etc/apt/sources.list to:
Here is informative content about — what they are, which one to choose, how to verify them, and where to get them. 1. What is a Debian 11 ISO? A Debian ISO is a disk image containing the files needed to install or run Debian 11 (Bullseye) without an existing OS. You write it to a USB drive or DVD.
If you are starting a new project, consider instead — it has newer software and longer active support. But if you specifically need Bullseye (e.g., legacy software compatibility), the above covers everything.