Download from here

df -h (show disk space) free -m (show Ram Usage)

There are not too many Firefox add-ons specific to Ubuntu Users. However I found these three add-ons really useful.With Firefox Notify add-on, you can receive all Firefox notifications through Ubuntu's native d-bus notification system. Works for Gnome as well as KDE environments. It may work on other distros too, you have to try it yourself.(The link is down. Use the command below)Edit: Also available in official Ubuntu repositories:Lets you search Ubuntu packages right from Firefox search box.Download from here This is really useful add-on for Ubuntu users. This add-on allows you to select shell commands from any web page and execute them just by a simple right click.Install it (from the link below) and test it on following commands:This means that adding a ppa from any webpage is really simple :)Download from here You may also like: 2 Simple Chrome/Chromium Extensions for Ubuntu Users