apt.txt

apt-get install pkg_name[-]
	suffix with - to remove

apt-get upgrade 
	upgrades all packages
	will "keep back" packages in case of broken dependencies (absent
	dependencies), or if a package has an additional dependency
	(resolve with apt-get install)

apt-get dist-upgrade
	upgrades everything, handling relationship changes

apt-get clean; apt-get autoclean
	remove cached packages under varying conditions

/etc/apt/apt.conf
	config file
	contains APT::Default-Release "version";

/etc/apt/preferences
	allows pinning of packages
	pin priorities allow packages to be blocked from installation,
	or from being upgraded, plus intermediate behaviours