Ubuntu Linux can be upgraded using GUI tools or using traditional command line tools such as:
apt-get command - apt-get is the command-line tool for handling packages.
aptitude command - aptitude is a text-based interface to the Debian GNU/Linux package system including Ubuntu Linux.
apt-get update: Update is used to resynchronize the package index files from their sources via Internet.
apt-get upgrade : Upgrade is used to install the newest versions of all packages currently installed on the system
apt-get install package-name : Install is followed by one or more packages desired for installation. If package is already installed it will try to update to latest version.
Get update software list, enter:
$ sudo apt-get update
Update software(s) i.e. apply updates and patches on Ubuntu Linux
$ sudo apt-get upgrade
To upgrade individual software called foo type command:
$ sudo apt-get install fooOR
$ sudo apt-get install apache php5 mysql-server
