Using a Ubuntu 12.04 laptop as monitor for Raspberry Pi
This is not really that difficult once you know it, but I had to combine instructions from several posts and fiddle around a bit, so I thought I'd write down the different steps. This is assuming you have an external screen attached to the Raspberry Pi to do the configuration.
1. Find out the IP address of your laptop
To do this, you go to system settings. There you will have to turn the switch icon on the top right to "On". You will also need to connect your laptop with an ethernet cable to your Raspi to see the IP address.
2. Assign an IP address to the Raspberry Pi
Start your Raspberry Pi, log in and then do the following, using an IP address that is the same as your laptop's except for the last number:
$ sudo ifconfig eth0 10.42.0.2
You can check that the IP address has been assigned like this:
$ hostname -I
(If you do this before assigning an IP address you should just get a blank line)
Once you have done that, you can "ping" your laptop with the laptop's IP address. Stop this process with Ctrl+C once you've seen some responses:
$ ping 10.42.0.1
The IP address is only assigned for this session. There are some instructions here to assign the IP address at boot - but remember to replace the command.txt file by the original again before you try updating your OS through your home internet connection. It won't work otherwise (at least that's what I experienced!): http://pihw.wordpress.com/guides/direct-network-connection/
3. Install TightVNCServer on the Raspi and a VNC Viewer on your laptop
On the Raspberri Pi you install the Tight VNC Package :
$ sudo apt-get install tightvncserver
On the laptop, install a VNC viewer, for example
$ sudo apt-get install xtightvncviewer
4. Access Raspberry Pi through your computer via ssh and view interface through Xvnc
Now you can open a terminal on your laptop and ssh into your Raspberry Pi:
$ ssh pi@10.42.0.2
Then run TightVNC server from your terminal, and start a VNC server (the example below starts a session on VNC display zero (:0) with full HD resolution):
pi@10.42.0.2's password:
pi@raspberrypi ~ $ tightvncserver
In another terminal window on your laptop, start the VNC viewer with
$ vncserver :0 -geometry 1920x1080 -depth 24
$ xtightvncviewer 10.42.0.2:0
That's it. Most of the instructions in this post are taken from elinux.org, which also tells you how to creat a vncboot service in /etc/init.d. This is quite handy, as then you can just type the following to start the VNC server with your preset preferences:
$ sudo service vncboot start