Performing Debian Major Version Upgrade

1. Upgrade the current system

sudo apt update
sudo apt full-upgrade -y
sudo apt autoremove
sudo systemctl reboot

2. Update configuration to the new codename

1. In /etc/apt/sources.list, change the Debian codename from the old codename to the new codename
2. In /etc/apt/sources.list, comment out <old-codename>-backports

3. Upgrade to the new system

sudo apt update
sudo apt full-upgrade -y
sudo apt autoremove
sudo systemctl reboot

4. Confirm the new system is functional

sudo systemctl status

5. Restore backports

In /etc/apt/sources.list, uncomment <old-codename>-backports and replace <old-codename> with <new-codename>