How to update the system using the terminal?

Question

I normally update my Linux Debian using the Update manager, but how can I do that using the terminal?

Solution

On Debian and most Debian-based distributions (including Ubuntu):

1. Refresh the package database: apt update, apt-get update or aptitude update

2. Install new packages: apt upgrade, apt-get upgrade, or aptitude safe-upgrade.

   apt(-get) upgrade only updates existing packages and is safer, while apt full-upgrade or apt-get dist-upgrade may install new dependencies or remove existing ones.

(See also: apt-get vs aptitude)

Comments

[karatedog]

And when do I know that a system restart is required after upgrading (let's say because of a kernel upgrade)

[Chong]

Most update(except kernel and nvidea) won't require system restart. Because unlike Windows, open file won't prohibit the writing over it. However sometimes when running service is updated and you want to use the new version immediately, you merely need to restart that service alone(if not done by the upgrade script already).