Monitor, Linux and KVM help

[James Specht]

We are converting our entire site over to Raritanâ s KVM system. No more monitors and keyboard spread all over the place! It works great with just about every system we have, except Red Hat linux systems. Here is the problem. The monitor (a Compaq 1701 LCD flatpanel) works fine when directly connected to the system. Once we attach the linux system to the KVM (using the same monitor) boot screens and command mode are fine, but the moment you go into the GUI mode we loose the picture.

We contacted Raritan for support and their solution was â during boot up and command mode linux is sending a CRT single to the monitor but once you enter the GUI mode linux switches to a driver for the graphic card and monitor. Install the correct driver for the monitor and graphics card in the command mode and this should solve the problem.â

I didnâ t know linux did monitor drivers in command mode. Anyone know how to do this or if it can be done? What I have found so far says linux doesnâ t do monitor drivers.

Points will be awarded to all answers and a 10 spot for the answer that gets this working.

I also wish to note that I will be working on converting other systems to the KVM today. But I will check this thread as often as possible throughout t

[Mark Grant · Accepted solution]

I don't actually know anything about KVM but perhaps I can help point you in the right direction.

THe general rule is for Linux to use a CRT device as Raritan have said. When X is running for the GUI, it is true that the drivers are in X itself, not part of the linux kernel.

If, however, you use the Linux frame buffer, the situation changes so that the device driver is initialized and used for text mode and GUI stuff from boot to shutdown.

Maybe you should try using the linux framebuffer. Maybe it won't help but might point you in the right direction.

[Patrick Van Humbeeck]

I think Mark's idea should work - I have a monitor on a KVM switch (not the same make tho) running in framebuffer and it works flawlessly. It's worth a try (unless you play 3d games at work :)

[Dave Falloon]

I currently use an el cheapo startech KVM to split a monitor for my winXP box and my debian box. The monitor itself works when plugged in to the server, but at what refresh rate? Your KVM box may have a refresh rate limit that is lower than that of the monitor. Perhaps the linux box is sending video outside of the KVM scan range? Is that a possibility?

Can you see the text boot up screen/grub menu?

Are you running any higher res text mode during boot up?

Everything from here on assumes you can see the grub boot menu.

You are using red hat so I assume you use grub, so you can try different text modes during boot if you add vga=ask to your kernel line, ie:

kernel /boot/vmlinuz-2.4.18-4 ro root=/dev/hda2 hdd=ide-scsi

becomes:

kernel /boot/vmlinuz-2.4.18-4 ro root=/dev/hda2 hdd=ide-scsi vga=ask

Then you should get a list of the available text video modes during boot up. Try them all with the KVM switch maybe you'll find one that works.

Dave

[James Specht]

Thanks for the ideas. I'll get a chance to test one of our linux servers tomorrow. I hope one of these solutions works.

--Jim

[James Specht]

Mark, It looks like your solution will solve th e problem. My problem now is getting lilo to boot under the new kernel. I'll start another thread on that one. Thanks for the push in the right direction.

Patrick, I gave you 3 points just for the 3D gaming at work line!

Dave, I have tried so many res settings in X to see if the KVM would hold but no luck. At one point I thouht we had it but if gaves out after about 5 minutes.

Thanks guys for the help here. Look for the new thread on lilo.conf.

--Jim