I normally update my Linux Debian using the Update manager, but how can I do that using the terminal?
On Debian and most Debian-based distributions (including Ubuntu):
Refresh the package database:
Install new packages:
apt-get upgrade, or
apt(-get) upgradeonly updates existing packages and is safer, while
apt-get dist-upgrademay install new dependencies or remove existing ones.
(See also: apt-get vs aptitude)