Package manager used by Debian-based Linux distributions. Front-end for dpkg - easy dependency resolution and least amount of operations taken.

❕ In scripts, apt-get should be used, as apt is intended to be used interactively (it does not have stable interface).

Documentation: apt documentation on Ubuntu's manual pages

Standard operations:

Description	Command	Notes
Show help	apt
Checking for new updates	sudo apt update
Installing updates	sudo apt upgrade	Disregard suggestion to use with auto-confirm switch -y as it's dangerous (it's best practice to review proposed changes). Capable of restarting interrupted upgrade process (issued by executing again).
Automatic cleanup	sudo apt autoremove	Most distributions clean unused packages automatically. Useful when there's no disk space left on root partition.
Searching for package	sudo apt search KEYWORD
Installing new package	sudo apt install PACKAGE_NAME
Removing package	sudo apt remove PACKAGE_NAME	❗ This will break system if removal of core package will get forced.
Removing package (and its configuration)	sudo apt purge PACKAGE_NAME	❗ This will break system if purge of core package will get forced and make recovery harder.
Lists installed packages	apt list --installed
Lists upgradable packages	apt list --upgradable
Full upgrade	sudo apt full-upgrade	❗ Unsafe - unlike apt upgrade it'll remove packages as needed.
Dist upgrade	sudo apt dist-upgrade	❗ Unsafe - unlike apt upgrade it'll remove/change packages as needed to upgrade to next release (potentially to non-LTS release).