How to update your Raspberry PI’s firmware?

Type in the following lines (terminal window):

• sudo apt-get install ca-certificates git-core binutils
• sudo wget https://raw.github.com/Hexxeh/rpi-update/master/rpi-update
• sudo cp rpi-update /usr/local/bin/rpi-update
  
• sudo chmod +x /usr/local/bin/rpi-update
• sudo rpi-update

Next time you only have to type the last line to update your firmware (sudo rpi-update)

To check your current firmware version type:

• /opt/vc/bin/vcgencmd version

Resource:
http://wrightrocket.blogspot.nl/2012/06/keeping-your-raspberry-pi-fresh.html