There is one problem that can arise when using a KVM switch with a modern Linux distribution. This problem has to do with the latest releases of Xorg. Because Xorg no longer uses the xorg.conf file, it depends upon receiving identification signals from the monitor in order to automatically adjust the display. On a single system/single monitor setup this works perfectly. But in some instances a KVM switch will get in the way and the X Windows display will be far from ideal (and some times not even usable). How do you get around this situation? In this article you will read a few tips that will help you get around this.

Choosing your KVM

There is, unfortunately no way to know which KVM switch will work well with modern Linux setups. I have tried four different KVM switches with modern Linux distributions – all with varied results. Here are the KVMs I have used (and their results):

• Belkin Flip (USB): Switched between machines quickly, but lead to freezing with Ubuntu Linux. Couldn’t detect monitors so resolution was poor.
• IO Gear Miniview 2-port (USB): Switched between machines quickly, no freezing. Couldn’t detect monitors so resolution was poor.
• Generic 4-port KVM (USB – purchased on Ebay): Poor switching, constant freezing, and couldn’t detect monitor.
• IO Gear 4-port Miniview (USB): Easy switching, no freezing, monitor detected so resolution was perfect.

So from the above list, you would obviously want to go with the IO Gear 4-port miniview. It’s an inexpensive solution (approximately $70.00 USD) that will give you no problems.

Using your current KVM

What if you already have a KVM switch? There are options. The first option is to manually configure your /etc/X11/xorg.conf file (For more information on the xorg.conf file check out the xorg.conf articles on Ghacks.net). This can lead to problems when you’re not sure what your graphics card is or the resolution of your monitor. Because of this, you might have to do a bit of research before you continue. If you know you are using an NVidia card you are lucky, you can use the Nvidia Settings tool (read about it in my article “Adding  a widescreen monitor in Linux“.) You can use this tool to generate your xorg.conf file for you.

If you do not want to have to monkey around with configuring xorg.conf, you have another solution – one that isn’t perfect, but will work in a pinch (and one I have used when dealing with certain on-board graphics chips like Intel). Plug your  monitor, keyboard, and mouse directly into your Linux machine and let it boot. Once you have your desktop up and running unplug the monitor, keyboard, and mouse and plug them back into the KVM. Plug the KVM cords into your Linux box and your Linux machine will be up and running. Fortunately the Linux machine won’t have to be rebooted for anything any time soon. It’s not an ideal solution, but it will work for you. Just remember, if you have to reboot you need to switch those cables around until the machine is back to the GUI desktop.

Final thoughts

Ideally you will purchase a KVM switch like the IO Gear 4-port Miniview that will give you no problems. Otherwise you might have to toy with a work-around or two in order to get your Linux box working with your KVM. This is the price the user-community has to pay for having a modern distribution that doesn’t require configuring X (at least not single-system setups).

But now the Linux community has distributions, such as Fedora 10, that do not default to using  an xorg.conf file. This is great news for many users. However, it’s bad news when, for some reason, X isn’t working or you have specific needs that the default isn’t meeting. With that in mind we’re going to break down the xorg.conf file so that you will be able to troubleshoot your X Windows configuration when something is wrong.

The Basics

The first thing you need to know is that xorg.conf (located typically in /etc/X11) is broken up into sections. Each section starts with the tag Section and ends with the tag EndSection. Each section can be broken into subsections as well. A subsections starts with the tag SubSection and ends with the tag EndSubSection. So a typical section with subsections contains the tags:
Section Name
Section Information
SubSection Name
SubSection information
EndSubSection
EndSection

Of course you can’t just use random sections. There are specific sections to use. Those sections are:

• Files – pathnames for files such as fontpath
• ServerFlags – global Xorg server options
• Module – which modules to load
• InputDevice – keyboard and pointer (mouse)
• Device – video card description/information
• Monitor – display device description
• Modes – define video modes outside of Monitor section
• Screen – binds a video adapter to a monitor
• ServerLayout – binds one or more screens with one or more input devices
• DRI – optional direct rendering infrastructure information
• Vendor – vendor specific information

Each section will have different information/options and is set up:

Option Variable

Let’s take a look at a sample section. We’ll examine a Device section from a laptop. The section looks like:

Section "Device"
Identifier "device1"
VendorName "VIA Technologies, Inc."
BoardName "VIA Chrome9-based cards"
Driver "openchrome"
Option "DPMS"
Option "SWcursor"
Option "VBERestore" "true"
EndSection

The above section configures a Via Chrome video card (often a tricky one to get running) using the openchrome driver. Here’s how this section breaks down:

• The identifier (labled “device1″) connects this section to Screen section with the Device “device1″ option.
• The VendorName and BoardName both come from the make and model of the video adapter.
• The Driver is the driver the video card will use.
• Option “DPMS” – this enables the Display Power Management System.
• Option “SWcursor” – this enables the cursor to be drawn by software (as opposed to the HWcursor drawing by hard ware).
• Option “VBERestore” “true” – allows a laptop screen to restore from suspend or hibernate.

The lengthiest section of your xorg.conf file will most likely be your Screen section. This section will contain all of the subsections that contain the modes (resolutions) for your monitor. This section will start off like this:

Section "Screen"
Identifier "screen1"
Device "device1"
Monitor "monitor1"
DefaultColorDepth 24

Notice how the above section references both a device and a monitor. These will refer to other sections in the xorg.conf file. This section also contains the DefaultColorDepth which will define the default color depth for your machine. In the case above the default is 24. Now, take a look below at the SubSections of this section:

Subsection "Display"
Depth 8
Modes "1440x900" "1280x800"
EndSubsection
Subsection "Display"
Depth 15
Modes "1440x900" "1280x800"
EndSubsection
Subsection "Display"
Depth 16
Modes "1440x900" "1280x800"
EndSubsection
Subsection "Display"
Depth 24
Modes "1440x900" "1280x800"
EndSubsection
EndSection

As you can see there is a SubSection for four different color depths. Included in those subsections is the default 24. So when X reads the DefaultColorDepth option it will automatically attempt to set the modes configured in the Depth 24 subsection. Also notice that each subsection contains two resolutions. X will attempt to set the first resolution (in the case above our first default is 1440×900) and move on to the next if it can not set the first. Most likely X will be able to set the first.

Final Thoughts

This is only meant to be an introduction to the xorg.conf configuration file. As you might guess, xorg.conf, can get fairly complex. Add to the complexity numerous options available for each section and you have a valid case to make sure you RTFM (read the fine man page.) And the man page is an outstanding resource to find information on all of the available options. To read the man page issue the command man xorg.conf from the command line.

By having a solid understanding of the xorg.conf file you won’t have any problems fixing a fubar’d X installation or tweaking your xorg.conf file to get the most from your new video card.

With the advent of Fedora 10 xorg.conf does not, by default, install an xorg.conf configuration file. In fact, I had Fedora 10 up and running with an NVidia GeForce 6600 card, with no xorg.conf file. Problem was, I couldn’t get the installation to run in 1200×1024 resolution. Not until I jumped through a few hoops.

One of the first things you should do, when you finish an installation of Fedora 10 is check in /etc/X11 to see if there is an xorg.conf file. If there is not you need to issue the command Xorg -configure :1. What this will do is generate a default xorg.conf file based on your hardware.

Your next step can be tackled in a couple of ways. You can edit the xorg.conf file by hand (for advanced users) or you can install the system-config-display application with the command yum install system-config-display. Once you get that installed you can run the application (as root) with the command system-config-display. From that point the GUI tool should be pretty straight foward to use.

Of course, if you are using an NVidia card, you might have to install some proprietary drivers. Open up the Add/Remove Software tool and do a search for nvidia. Select the applicable drivers for your system if you need them. Once you install the drivers you should have the nvidia-settings tool. This will offer you some help in configuring your NVidia card with Fedora 10.

You will notice the default xorg.conf file generated is very bare-bones. And I understand that Xorg is going in a direction that doesn’t require an xorg.conf file. But there are chipsests out there, such as NVidia, who’s drivers still require an xorg.conf file. This, to me, seems as if Xorg is getting a bit ahead of itself.

UPDATE: I can’t confirm this but the above statement about Xorg going in an xorg.conf’less direction seems to only be applying to Fedora. If anyone has any information that would indicate other distributions are following suite, let us know. Thanks all!

Now I can’t complain too much…X Windows does work out of the box and does a fairly admiriable job. But when you want higher resolutions than the default, you might find yourself jumping through some hoops. I have to admit Linux will find itself in much greener pastures once Xorg no longer requires a configuration file. But I do hope the developers of the various chipsets can get on the same page as the Xorg developer team. If they can’t Linux is going to find itself with a limited selection of video cards it can work with.