As per this post on the Raspberry Pi Forum:
Modify the file /etc/apt/sources.list
by running sudo nano /etc/apt/sources.list
. Change wheezy
to jessie
in the first line, so it reads deb http://mirrordirector.raspbian.org/raspbian/ jessie main contrib non-free rpi
Modify the file /etc/apt/sources.list.d/raspi.list
by running sudo nano /etc/apt/sources.list.d/raspi.list
. change wheezy
to jessie
in the first line and add ui
to the end of that line. The line should read deb http://archive.raspberrypi.org/debian jessie main ui
Create the directory /home/pi/.config/autostart
by running mkdir /home/pi/.config/autostart
in the terminal. (Note the .
in front of config
.)
Run sudo apt-get update
in the terminal to update the apt
index files.
Run sudo apt-get dist-upgrade
to start the upgrade process. This will take a couple of hours. Whenever prompted to update a file during this process, choose the Y
option to accept the new file; if you don't want to be bothered with these prompts, then call apt-get
with the -y
option using sudo apt-get -y dist-upgrade
.
On first boot of Jessie you will see messages about:
Calling CRDA to update world regulatory domain
Wait until the messages stop then login as the user pi. You may need to run start x
to get the GUI to load up. This screen might go black as it loads the GUI this is fine.
When the GUI has loaded you can install all the new software packages by running:
sudo apt-get install rc-gui libreoffice libreoffice-gtk alacarte bluej greenfoot claws-mail
This will install the new GUI version of raspi-config, LibreOffice and its GTK extension, the Alacarte menu editor, the BlueJ and Greenfoot Java IDEs and the ClawsMail email client.
The GUI will need cleaning up:
To load the new version of the PiX GTK theme. (Note the . in front of themes) run ``
To prevent the ClipIt application from automatically starting on boot run sudo rm /etc/xdg/autostart/clipit-startup.desktop
To prevent the Wicd network manager from automatically starting on boot run sudo rm /etc/xdg/autostart/wicd-tray.desktop
To remove the huge list of application shortcuts in the “Other” menu run sudo rm –rf /var/lib/menu-xdg
To select to boot to desktop with autologin as the pi user run sudo raspi-config nonint do_boot_behaviour_new B4
To hide the menu shortcut to the Openbox window manager, whose functionality has been replaced by the Appearance Settings preferences application run sudo rm /usr/share/applications/obconf.desktop
If possible I would strongly recommend a clean install of Jessie, it's probably going to be less hassle then running all of these commands. Definitely backup anything important before you attempt the upgrade.