Tech: Multiple Computer Challenge

Lars Poulsen - 2021-09-04

Like many people from the technical world, I often have at least two computers on (or rather at ) my desk. They are both "desktop" computers; i.e. the computers sit under the desk, with the screen and keyboard on top of the desk. But the desk is not big enough to hold two sets of screen/keyboard/mouse and still have room for documents etc that I am using for reference as I work on the computer. The solution to this is called a KVM switch - the letters stand for Keyboard, Video and Mouse. It is a fairly simple device that allows you to get by with only one screen, keyboard and mouse for both/all the computers. You put the switch between the keyboard and the monitor, with the screen, keyboard and mouse plugging into one side of the switch, while cables on the other side go from the switch to each computer. These switches are readily available for two computers or four, for less than 50 US dollars. For more ports, it get quite expensive.

However simple this is, there are still options:

The video and keyboard options must match on both sides of the switch.

The setup I had been using for the last couple of years had

I found an offer for an inexpensive Intel-based Mac Mini (8GB, 2012) capable of running MacOSX Catalina, and decided to get it. I maintain a small program that has Windows and Linux versions, and I would like to have a Mac version. This was a good opportunity to get that capability. Of course, this meant that I would have to replace the 2-port KVM switch with a 4-port one. Which in turn would allow me to also bring in the very old PPC-based Mac Mini that has sat unused for a few years, but has sentimental value because it can still run my very old Mac programs from my long departed Macintosh SE 9-inch B&W that was my first home computer. Foolishly, I ordered a 4-port switch with HDMI video without checking everything first. After all, my 1920x1080p desktop display *prefers* HDMI input over VGA. I knew that I would need an adapter for the old mini, which had a DVI video output with a VGA converter adapter plugged in, but DVI to HDMI is *very* standard. The new mini came with HDMI video (only). I knew that both the Windows and Linux PCs had VGA ports, so I found a VGA-to-HDMI converter plug, ordered two of those and figured that would do the trick.

Amazon delivered the new switch the very next day, and I discovered that the VGA-to-HDMI adaper did not work, and neither of the PCs has an HDMI port. The windows machine has only VGA, the Linux machine has VGA and DVI. Okay, let's check it out with the DVI-to-HDMI adapter in the Linux PC. No dice. And by now I have spent 4 evenings on this project.

So in the end, I ordered a 4-port switch with VGA video, and my 2 PCs are back up again. In a couple of weeks, I may try to add the Mac minis to the cluster. I have decided that the VGA to HDMI converters are probably meant to install the opposite way: Plug into an HDMI computer and give me a VGA output, which means I am all set for both Macs. Except for the task of getting all the cables under that desk (including USB cables and powerfeeds to a half dozen external disk drives and cellphone charging and sync cables) properly labeled.

And I have a pile of stuff that I will not be using.


When I finally got everything back together again, the Linux box had two new problems that popped up at this time, but were really unrelated:

The OS for some reason would not let me login from the GUI desktop, only with the remote ssh login. This happened both with the root account and my normal user account. For two different reasons.

These two problems illustrate the frustrating state of Linux desktop systems: They are almost good enough to be simple to use, but then you hit a bump that may be a mild challenge for a professional sysadmin, but will be a complete showstopper for a newbie.

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