Ubuntu
14.04 -> 16.04
sudo apt update && apt upgrade sudo apt install update-manager-core sudo do-release-upgrade reboot sudo apt update && apt upgrade sudo apt autoremove
16.04 -> 18.04
sudo apt update && apt upgrade sudo do-release-upgrade reboot sudo apt update && apt upgrade sudo apt autoremove
18.04 -> 20.04
sudo apt update && apt upgrade sudo do-release-upgrade reboot sudo apt update && apt upgrade sudo apt dist-upgrade sudo apt autoremove