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Anomalous KVM event: messed up screen colors

Posted 05-02-2015 at 11:01 AM by flshope

This morning when I booted up my primary machine and started Libre Office Calc, which I use for my To-Do List, I saw that all of the colors had been significantly changed. For example, the greens and yellows were almost the same and were almost fluorescent in flavor. All of the colors had a different tint. Most solid lines in the spreadsheet display seemed to have dark shadows. I didn't check any other display applications, like the Image Viewer.

I did notice just after initial power on that the KVM switch (IOGEAR GCS1724) was set to machine 2 (my primary machine is 1) because that was the last machine I powered down the previous night. I manually switched the KVM to 1 during the boot. Previously, it always has been set to 1 before I do the power up.

Not knowing what else to do with a new anomaly, I just did what I was once used to doing 10 times a day with Windows*: I did a warm restart (restart without a power off). No help: the screwed up colors were still there. So I did a cold restart (full power off and power on). Still no change. It is important to note here that the KVM switch remains under power even when all the connected machines are powered off. It receives power through the USB connections as long as one of the switched machines has a hot connection to the main power supply (i.e., the 120 V wall socket). So I did a full power off again, but this time I turned off the main power strip through which all machines receive power. The lights on the KVM went out, indicating it would have to restart when power came back on. After powering up machine 1 again, the colors on Libre Office Calc were restored to normal. The KVM switch also has a hot key reset sequence, but I didn't try that.

Lessons learned: It is clear that the KVM switch was involved in the color anomaly and that a full power down of all machines and disconnection from the central power supply removed the color anomaly. It is not clear what set of initial conditions caused the anomaly. The possibilities include: (1) changing the KVM machine selection during boot, (2) machine 1 not being the last one powered down the previous night, (3) starting the boot of machine 1 with the KVM set to 2.

If I learn any more about this, I will post the results. I guess I should try to reproduce the fault. However, being fundamentally insecure about being able to keep my Linux boxes working at all, I am loathe to intentionally trying to induce faults in their operation.

*In fairness to Windows, I have not spent substantial time on a Windows box for perhaps 10 years. I think it is much better now.
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