Upgrade a Linux Server

sudo apt update           # Fetches the list of available updates
sudo apt upgrade          # Installs some updates; does not remove packages
sudo apt full-upgrade     # Installs updates; may also remove some packages, if needed
sudo apt autoremove       # Removes any old packages that are no longer needed
sudo apt-get dist-upgrade

do-release-upgrade # Digital Ocean specificCode language: PHP (php)

Ref: https://www.digitalocean.com/community/tutorials/how-to-upgrade-to-ubuntu-18-04