Update manager indicator notify you with available updates for the system. it shows up on the top panel of gnome shell interface with how many updates available, update name, brief information about the update and the size for each update.
From the update manager indicator menu your can click on update to get latest updates from added repository and you can upgrade them directly from the menu as well. Also you can adjust the refresh interval between each time to check for updates.
[How To]: Install Update Manager extension On Ubuntu 11.10 Oneiric Ocelot and Ubuntu 11.04 Natty Narwhal
Run Terminal ” Ctrl+Alt+t ” then type.
sudo apt-get update
sudo apt-get install gnome-shell-extension-updateindicator
To activate update manager extension, run Gnome Tweak Tool then turn on the update manager extension from shell extension menu.
In case you don’t have Gnome Tweak Tool you can install it.