thanx to https://feeding.cloud.geek.nz/posts/installing-debian-buster-on-gnubee2/
Upgrade to stretch (Debian 9) and then buster (Debian 10)
To upgrade to stretch, put this in /etc/apt/sources.list:
deb http://httpredir.debian.org/debian stretch main
deb http://httpredir.debian.org/debian stretch-updates main
deb http://security.debian.org/ stretch/updates main
Then upgrade the packages:
apt update
apt full-upgrade
apt autoremove
reboot
To upgrade to buster, put this in /etc/apt/sources.list:
deb http://httpredir.debian.org/debian buster main
deb http://httpredir.debian.org/debian buster-updates main
deb http://security.debian.org/debian-security buster/updates main
and upgrade the packages:
apt update
apt full-upgrade
apt autoremove
reboot
Then to bullseye (Debian 11)
- Make sure the system is fully up to date
apt update
apt full-upgrade
apt autoremove
reboot
- Edit
/etc/apt/sources.list
- replace each instance of buster with bullseye
- find the security line, replace buster/updates with bullseye-security
- this is an example:
deb http://security.debian.org/ bullseye-security main contrib non-free
deb http://httpredir.debian.org/debian bullseye main contrib non-free
deb http://httpredir.debian.org/debian bullseye-updates main contrib non-free
- Again upgrade the system
apt update
apt full-upgrade
apt autoremove
reboot