Aktualizace zdrojů z Stretch na Buster:

sed -i 's/stretch/buster/g' /etc/apt/sources.list

Aktualizace zdrojů z Buster na Bullseye:

sed -i 's/buster\/updates/bullseye-security/g' /etc/apt/sources.list
sed -i 's/buster/bullseye/g' /etc/apt/sources.list

Aktualizujeme balíky:

apt update
apt upgrade
apt dist-upgrade