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Dual Displays On Solaris

If you've got two monitors and two video cards, there's a pretty simple way to hook up both monitors to a single Solaris desktop and use them side-by-side. One of the monitors will be the primary monitor (the one you log in on), and the other will be a sort of virtual extension - if you move the mouse pointer sideways off the primary screen, it'll appear on the second screen. Display windows can't straddle the boundary between screens, but having two screens (and multiple virtual desktops on each) can be really handy.

Here's how to do it:

Hook Up The Hardware

Duh! Plug both video cards in, and hook up both monitors. Turn the monitors on.

Verify Or Create Device Definitions

Take a look in the /dev directory for defined framebuffer devices. Use this command:

    cd /dev
    ls -l | grep fb
You should definitely see an entry for fb0 - that's your primary frame buffer, or primary video card. If you also see an entry for fb1, that means your system already knows about the secondary frame buffer (second video card), so you may not need to do anything more with regard to device definition.

If you don't see an entry for fb1 (or if something odd is going on and you just want to force the system to reexamine the attached devices), you can tell the system to rescan devices as part of a reboot. Close down all your nonessential processes, root the box, and then type this command:

    reboot -- -r
Yes, it's weird-looking. It's "reboot space dash dash space dash r". When you run this command, the machine will reboot immediately, and when it comes back up it will re-check all connected devices and generate entries in /dev as needed. After the reboot has finished up and all the dust has settled, go back into /dev and you should see entries for both fb0 and fb1, your two video cards.

Create Or Edit Your Xservers File

At this point, the hardware is configured for use; all you have to do now is convince the X window manager software to use both video cards.

There's a file named /usr/dt/config/Xservers that contains the display definition information, and some folks just wade into that file and start hacking away. A much safer approach is to modify (or create, as needed) an Xservers file in /etc/dt/config that defines your dual-head video configuration.

If you screw up the Xservers file in /etc/dt/config, the system will fall back on the Xservers file in /usr/dt/config, and you've got the chance to fix your mistake. If you only have one Xservers file on the system and you screw that file up, you may have a little more trouble making repairs.

So - root the box, then go into /etc/dt/config (create the directory if you need to) and create or edit the Xservers file. Here's an example XServers line that defines two monitors and sets the color depth to 24 bits on each:

:0 Local local_uid@console root /usr/openwin/bin/X -dev /dev/fb0 defdepth 24 right -dev /dev/fb1 defdepth 24 left

NOTE! NOTE! NOTE! The preceding Xservers file line is meant to be put in the Xservers file as a single line, with no leading white space. I let it wrap on this page so that it's easy to read and print, but it's all just one big long line in the Xservers file.

You can use leading pound signs to indicate comment lines in the Xservers file, if that sort of thing interests you. In this example, we define frame buffer 0 as the "right" side and frame buffer 1 as the "left" side - this just tells the X window manager how to handle the mouse positioning behavior between the two screens.


Root the box and type reboot, and when it comes up you should see your normal login screen on the primary display. Log in, and voila! - your second screen pops to life. If you've fouled up somehow and reversed the right and left monitors, the simplest thing to do is just swap the cables.

So, there you have it - now you're running two monitors at once. It really is quite slick, isn't it?

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