# sources for debian jessie
deb http://ftp.us.debian.org/debian/ jessie main non-free contrib
deb-src http://ftp.us.debian.org/debian/ jessie main non-free contrib
deb http://security.debian.org/ jessie/updates main non-free contrib
deb-src http://security.debian.org/ jessie/updates main non-free contrib
#sources for debian bullseye
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
anschließend ausführen:
apt-get update
root@DebianBullseye:/# This APT has Super Cow Powers. ;-)