an iPad as an extra screen for Linux

When I’m home, I am surrounded by monitors. It is like returning to a Mission-Control-influenced womb. Still, while I am definitely a fan of being gently irradiated by millions of pixels, I am also a fan of travel, and there is a drastically limited number of 27” monitors that will fit into your average backpack. Hence, I’ve been thinking for a while about ways to use the lovely screen on my iPad as an extra terminal. I usually take it anyway, so it’s not even costing me extra luggage space.

The harder question is how to do it. The most obvious method would be to connect a VNC client to a given session on my laptop, then set up Synergy to connect from that session to a local server. This setup means I get a full X session on the iPad. The drawback is that VNC tends to be horribly slow over wireless.

Another possible solution would be to use something like iSSH on the iPad, and connect Synergy directly using a client on the iPad. This runs into problems too: first, the only available Synergy client for the iPad seems to require jailbreaking, and doesn’t appear to work reliably anyway. Foiled again!

Not all is yet lost for our hero, however. These two methods can be combined to create a rickety construction of fearsome Goldbergian beauty. We’ll need one more component to make this work: tmux, which will allow you to connect two terminals to the same shell session.

First, we set up a VNC server and client. “apt-get install vnc4server xvnc4viewer” will do on Ubuntu. We start it up: “vncserver :1”, and connect with “xvnc4viewer”.

Now, we can use Synergy (again, apt-get install synergy) to connect the :1 display to our local server. My conf looks a bit like this:

section: screens
section: links
    left = left
    right = rhino

I run “synergys -f” in a terminal on my normal desktop, then “synergyc -n left localhost” in a terminal inside the vnc session. I can now transfer the mouse between the two sessions.

The final part of the puzzle is tmux (apt-get install tmux). I can then create a tmux session inside the VNC session with

tmux -S /tmp/pair

(You might consider opening up the permissions on /tmp/pair if you were sharing with another person, but we’re only sharing with ourselves so it should be fine as it stands.)

I then install iSSH on the iPad, and ssh into my box. I then run

tmux -S /tmp/pair attach

And we are now done! When I move my mouse left off my main screen, while I don’t see the actual cursor, the shell in the window gets keyboard focus, and I can run irc, compilation, or whatever other textual glory I desire. All the other windows can be exiled to a virtual desktop gulag I don’t visit (or more professionally set up to run headlessly somehow), and strangely, the whole setup seems to work remarkably well.