How to use iMac as external monitor for ubuntu laptop

Question

I have a 13 inch laptop running ubuntu and an iMac running OSX. I'd like to use the iMac as an external monitor for the laptop.

The laptop has VGA and HDMI, and ubuntu 14.04.

Related:
https://apple.stackexchange.com/a/87666/109005
https://superuser.com/q/540547/372305

Solution

I had the exact same problem. I got this working reliably with a combination of xpra and Xephyr. This solutions of course uses your local network, through ssh, to make an remote display.

You need xpra installed on both of your devices and Xephyr on your Ubuntu machine. There is a repo for Ubuntu, which installs Winswitch - which xpra is part of. Winswitch has quite a few cool features.

Anyway here is how I got it to work:

On your Ubuntu machine in terminal:

xpra start --exit-with-client=yes --speaker=disabled --start-child="Xephyr :200 -ac -screen 1920x1080" :100

DISPLAY=:200 lightdm-session 'gnome-session --session=ubuntu'

Where "200" is the X11 port which Xephyr connects to, and "100" is the port made available over the local network.

On your Mac in terminal:

/Applications/Xpra.app/Contents/MacOS/Xpra attach ssh:[email protected]:100

Needless to say a this solutions is dependent on a wired network.

Comments

[Daniel]

I'm under the impression synergy and x2x allow you to share keyboard/mouse/clipboard etc between the two operating systems. What I want is to use the iMac as an external monitor for the ubuntu laptop; that means I'd be seeing/using ubuntu there as well instead of OSX.

[Pontomedon]

Newer versions support the "start-desktop" command which means you get a full desktop without needing to invoke Xephyr: "xpra start-desktop --start=somewindowmanager --exit-with-client=yes"

[Aaron Wallentine]

@Daniel that is correct ... Synergy is a "software KVM" .. it doesn't let you extend your desktop to another computer, but rather control 2 (or more) computers with a single keyboard/mouse. Haven't used "x2x" but it looks like basically the same thing. But that's not the same as using a second computer as basically an extra monitor for the first, over the network ...