Update Drupal using Drush

Drush is a command line shell and scripting interface for Druapl. Updating Drupal to latest version is easy with Drush.

sudo su 
apt-get install drush

Check new Drupal updates available. Enter inside the Drupal installation place/folder and apply following commands.
cd /usr/share/drupal7
drush up -n | grep available
drush up

You can find more Drush commands from following link,
http://drush.ws/

Drupal installation
https://help.ubuntu.com/community/Drupal