I have at least four machines running at all times – all using one monitor. Not only does space dictate this setup, so to does budget. Because of this I am relegated to using a KVM switch. If you’re not sure what a KVM switch is, it is a device that allows you to use multiple machines with only one monitor, mouse, and keyboard.
Some KVM switches even allow the sharing of a single audio output source (speakers).
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).