Commands for updating ubuntu
Step 3: Finally use the distribution upgrade command.This command also intelligently handles changing dependencies with new versions of packages.Lets take a look at some of the commands to help keep you secure and up to date with all the open-source goodness.
I would recommend running this before you run the upgrade commands to make sure you are getting all the available updates.
Open the terminal from the taskbar or application menu: First, update your system's package list by entering the following command: Generally speaking, doing this regularly will keep your installation up to date, in that it will be equivalent to the latest released image available from raspberrypi.org/downloads.
However, there are occasional changes made in the Foundation's Raspbian image that require manual intervention, for example a newly introduced package.
Some major, very- and incompatibly-different versions get packages.
For instance, Python 2.6, Python 2.7, Python 3.1 all live in separate packages on Ubuntu.