There are a few ways to upgrade Raspbian to the latest version.
1. If using NOOBS then press SHIFT on your RPi’s keyboard when your RPi boots up and the screen saying Press SHIFT for recovery mode and reinstall Raspbian. However, this wipes all files off your Raspberry Pi’s SD Card.
2. If not using NOOBS then use a normal PC to write a new Raspbian image to the SD Card. Then plug the SD Card into the RPi and then boot the RPi up. This wipes all files off your Raspberry Pi’s SD Card as well.
3. However, there is another way to update Raspbian to the latest version. Also this one does not wipe your Raspberry Pi’s SD Card’s files.
To update Raspbian using this way, open up the Terminal and type the following:
sudo apt-get update
sudo apt-get -y upgrade
Sometimes you may need to install other software as well. For example, Raspbian Kernel Version 4.4 required the following extra commands to be typed into the Terminal:
sudo apt-get install piclone geany usb-modeswitch pi-bluetooth
sudo apt-get install python-pigpio python3-pigpio
Even better, this method to upgrade Raspbian to the latest version doesn’t wipe any data off of the Pi’s SD Card.
Epic Chas Gamer 😎