KVM Problems

[Alanex]

Not really Desktop Hardware, so I'll post it here...

I've used PCLOS 2007 before, lasted around 6 months or so and then my laptop died. So I'm now trying to get back to using Linux again. As things have progressed steadily through all the various distros, I decided to try a few of them yet again before sticking with one. I have to admit, PCLOS was not my decided upon choice. However, the support I got from the unnamed distro *coff*fedora*coff* kinda put me off it, despite liking the Gnome environment. Anyway, the problem I have seems to be a fault with a few different distros. The only 2 that worked, if I remember correctly, were OpenSuse and CentOS, though I'd have to try them again to confirm that.

The problem is that my installation only works if I remove my KVM switch and plug the monitor straight in to the PC. On all the distros I've tried, including PCLOS, it won't let me boot into the GUI when I'm using the KVM. I've manually set up the xorg.conf file which runs perfectly fine, as long as the monitor is directly connected to the PC.

From googling, it would appear that it's down to the EDID not being available due to the KVM? Ok, fair enough, the KVM is cheap and nasty, but it does what's required of it. If I've manually setup my xorg.conf file, then why is it still trying to query the EDID? and more importantly, why is it just failing instead of falling back on the xorg.conf file?

I can't remove the KVM switch and I'm not really interested in buying a new, more expensive one when this one works fine. Linux/xorg appears to be the problem. I don't understand the need of an xorg.conf file if it doesn't get used. In fact, it's clearly using it when the monitor is plugged in directly, as the screen resolution couldn't be changed above 800x600 until I set up the xorg.conf file manually, so why doesn't it use it when I use the KVM switch?

Any help greatly appreciated, not sure I wanna go back to OpenSuse.

[ThirdOfSix]

It would help to know a bit more about your hardware.

First, what make and model is your KVM switch, and how many ports does it have?

If nothing else, does it have an external power supply and are you using it?

Some of the early and or current cheap switches are set up to get their power from the PS2 port. On some motherboard/bios combinations, there is no power there at the beginning of the boot process.

More about that in a bit.

Also, you need to tell us the make and model of your monitor and what interface it uses.

The make and model of your video card would help too.

I have used several KVM switches and on the cheap ones, one of the inputs is connected to the monitor on start up by default. If you do not have external power on the switch, it will probably always power up with that one port as the default. So, make certain that that is the one you have your computer on during boot.

If you use an external power source, they will normally default to whatever computer was in use last.

On some of the newer ones that do remember the monitor information and pass it on correctly, the power supply is optional but if you shut down the computer that is providing the power to store that information, they will forget the info without it under certain usage patterns.

On the cheap ones, you need to manually switch the KVM to the computer you are about to boot each time you boot a computer.

Some of the early but smart for their time KVM switches, will store and pass on the information from the mouse and monitor but are not able to work with some of the newer hardware. They are not capable of storing all the required parameters. They do pass on the information on boot if the computer is manually selected.

Unfortunately, some operating systems and some linux distributions do not only check this information at boot time so, if you switch away from some computers for too long and then switch back, things won't work right. I have a wireless mouse keyboard combination that works fine until the first time that the system polls the KVM for the information when it is not connected. Then, the mouse quits working even though the keyboard does. My solution to that is to just use a separate hardwired mouse for each computer and only allow the KVM to provide the keyboard and monitor connection.

If connection a power supply does not work, it is possible to manually edit the Xorg.conf file such that the system can be set up for a particular monitor only. Then, the system will not get confused on start up. Somewhere on line is a good document by the group responsible for writing the standard for the X system that explains what entries are needed in order to make this happen. It has been a while since I read it.  So, I do not remember the particulars at the moment.

You have not said how many computers you have connected to your switch and what operating systems they are running.

If your monitor has two inputs, you may be able to set your system up such that one input on the monitor is always connected to a particular computer that does not work with the KVM. Then, you just select the computer at the monitor. I do that with one of mine.

Anyway, I am pretty certain the a little research on the X system documents will give you the information to allow you to set up your system to work with your monitor at a fixed resolution and scan rate with no problem.

[Odessa888]

Third of Six, thank you so kindly for your response to OP's question.  I too have a number of machines on a couple of KVM switches and several machines direct to monitor. The direct to monitor ones come up just fine, the KVM connected ones don't.  I am not using a separate power supply with my KVMs and it had not occurred to me until reading your post that is most likely my problem.  In fact the only distros I can get to come up on the KVM based systems are DSL and Dynebolic, so it isn't just a PCLinux problem. 

Your response just solved my KVM based problems with PCLinux, as well as bunches of others.  Thankyou.

[Bren]

It must have something to do with whether it's externally powered. I have a D-Link externally powered KVM that I currently use with 3 towers, and have no problems.  Of course, I make sure to switch the KVM to what ever tower I'm booting up, so it can poll the mouse and kb at boot.

[Texstar]

Have you looked at Synergy from the repos?

Synergy lets you easily share a single mouse and keyboard between
multiple computers with different operating systems, each with its
own display, without special hardware.  It's intended for users
with multiple computers on their desk since each system uses its
own display.

[wjt]

I had the same problem and hunted long and hard for the solution.  I finally found it on a Fedora forum.  I'll reproduce the post here:

From Link Disabled

I had the same problem when my computer boots up with the monitor
switched off. This problem occurs because the nvidia driver queries the
monitor for the modes it can support and disables those modes if the
monitor is switched off (or can't be queried because of the KVM switch)

You can get around this by saving the edid data from the monitor to a
file and load the file at X startup instead of querying the monitor
every time. Run nvidia-settings, select your monitor and "Acquire EDID".
Save the edid to some file. Then under the "Device" section of your
/etc/X11/xorg.conf file, add the line:

Option "CustomEDID" "CRT-0:/root/edid.bin"

assuming your monitor is called CRT-0 and you have saved the edid file
at /root/edid.bin

The Acquire EDID button is found under GPU 0->CRT-0.