i’ve long been using an external 22” monitor with my ubuntu linux powered X200 thinkpad. while ubuntu maverick (10.10) has some issues with attaching and detaching the second monitor and subsequent suspend–resume cycles (the second suspend after a detach would not resume, d’oh), ubuntu lucid (10.04.02) works just fine (as befitting a long-term-support release).

for quite a while i’ve had the old 20” monitor which i had been using previously sitting on my desktop along with an USB DisplayLink adapter — the idea being to hook the old monitor up as well as a third monitor¹. the displaylink driver provided by ubuntu lucid seemed to work properly — the monitor’s screen would turn green on connecting it and a framebuffer device (/dev/fb1) and so i tried various recipes floating around on ubuntu forums and elsewhere — all promising to achieve a grand unified desktop comprising all three monitors — and they either didn’t work or if they achieved the grand unified desktop it was unusable.

so, after another prolonged period during which the monitor and the displaylink adapter gathered even more dust, i tried a different approach: give up on the grand unified desktop goal and instead just try to make use of the monitor. the idea this time was to start up a VNC server, then use a VNC client to directly render the server into the framebuffer device (/dev/fb1) provided by linux’s displaylink driver. the vncserver bit is actually quite easy:

[sourcecode language=”bash”] vncserver -name hidden -geometry 1600x1200 -depth 16 :42 [/sourcecode]

which starts a VNC server for the :42 display.

the VNC client bit turned out to be a bit more difficult. ubuntu lucid does have directvnc client which is “a vnc client for the linux framebuffer device”². that client does seem to require keyboard and mouse access and in some configurations did not work at all or locked up my keyboard (not the mouse, though, funnily enough) or crashed the running X session, so no points on that one. further research luckily turned up vnc2dl by none other than quentin stafford-fraser one of the original VNC developers (and also the inventor of the webcam it seems). vnc2dl seemed a bit more promising and — after slightly modifying³ dldevice.c — did do the job:

[sourcecode language=”bash”] sudo vnc2dl :42 [/sourcecode]

next up was fusing display :42 to my main display :0 on a keyboard and mouse level so that i could just move the mouse pointer over to the left and end up on display :42 — here x2x (in the equally named ubuntu package) came into play:

[sourcecode language=”bash”] x2x -west -to :42 >/dev/null 2>&1 & [/sourcecode]

and, hey, presto!, both displays are linked mouse and keyboard wise.

only thing still bothering me was that cut and paste was not working. to fix that required adding

[sourcecode language=”bash”] vncconfig -nowin & [/sourcecode]

to my .vnc/xstartup file.

to have firefox run on display :42 required creation of a new firefox profile — i added that to .vnc/xstartup as well.⁴