Edit /etc/apt/sources.list
# main security
deb https://security.debian.org/debian-security bullseye-security/updates main
#deb-src https://security.debian.org/debian-security bullseye-security/updates main
# main mirror Indonesia
deb http://kebo.pens.ac.id/debian bullseye main
deb http://kebo.pens.ac.id/debian bullseye-updates main
# NON FREE
deb https://deb.debian.org/debian bullseye main contrib non-free
# BACKPORTS
deb https://deb.debian.org/debian bullseye-backports main
Update without new packages
# apt upgrade --without-new-pkgs
During upgrade, you need to restart some services.
Restart, open root terminal and make full upgrade (required more than 800MB)
# apt full-upgrade
Restart your PC.
Clean up unused installer
# apt-get autoclean && apt-get autoremove -y
If you get trouble connecting to internet (can not resolve servername) after upgrading edit /etc/resolv.conf
search 8.8.8.8 1.1.1.1
nameserver 127.0.0.1
nameserver 8.8.8.8
nameserver 1.1.1.1
Restart your networking
# systemctl restart networking
If you install dnsmasq and get trouble connecting to internet (can not resolve servername) after upgrading, edit /etc/dnsmasq.conf
#no-resolv
# dedetok 2021-08-18
no-resolv
server=8.8.8.8
server=1.1.1.1