How to update or upgrade Ubuntu

Ubuntu can be updated or upgraded from synaptic manager or command line. Update or upgrade can also be done through Update manager.
To update/upgrade Ubuntu open Synaptic manager : In the synaptic manager select the reload option and it will download Ubuntu update files. After the download completes, select the option Mark all upgrades. Then another window will appear, select the Mark option and then after click on Apply option in synaptic manager.

Synaptic manager to update Ubuntu.

To update or upgrade through Update Manager : Open the Update manager and select the option 'Check'. It will check for the latest Ubuntu software and latest Ubuntu version. After that select the option Install Updates.
If the new version of Ubuntu is released then there will be an option which will say "Upgrade Ubuntu to latest version".

To update or upgrade from Ubuntu command line : Type the following commands in the terminal.

$sudo apt-get update
$sudo apt-get dist-upgrade