While booting my webserver I hit the scroll lock key a couple of times to flip my kvm over to another machine that was updating. When I switched back the webserver was still on the initial boot screen with the progress bar, and it hadn't moved. So I hit escape to see what was going on and it was just stopped at some random message. I decided to give it some time so flipped back over and when I hit scroll lock the messages moved a bit.
In the end I found out that scroll lock stops the boot process.
When I was running a Belkin KVM I found that if I did not switch to the Windows computer during its boot sequence, it would change its Video parameters, or fail to boot properly. Though it was supposed to simulate a monitor even in the toggled state it was not perfect about it. I learned to always switch to the computer that I was booting or shutting down to prevent errors. To switch you had to double hit the scroll lock and than either the up or down arrow key. I still use the KVM when trouble shooting. It just sits ready to connect though only hooked to my workaday machine.
I don't sit where these machines are very often, but sometimes its easier to work at the machines than to do it remotely.
Are you sure that scroll-lock really stops the boot process and not only the output?
Well if it was just the output I would have expected it to zoom by really fast. This seemed to continue at normal speed and the processor and hard drive picked up with certain messages.
As the console is a ANSI terminal/VT100 emulation, I would expect it to stop output on Ctrl-S (or Scroll lock) and resum on Ctrl-Q. Would be a bug if it didn't.
But the scroll lock key just does that: it sends Ctrl-S/Ctrl-Q to the terminal emulation. So I would expect it only stops the screen output and not the underlying boot process.
Yes eberhard, that is what I meant to say with "(or Scroll lock)". It is generating the ASCII codes.
About the stopping of the boot process: I remember in very early (Unix) times, that when you did Ctrl-S and thus stopped output, the output buffer (somewhere in the TTY-handler) filled up, and when filled up the process was suspended. Could that still be the case?
Most KVM switches I ever had (or still have) have an alternative keystroke to CTRL - usually ESC.
So if the documentation says <ctrl>-<ctrl>-<home> then usually something like <esc>-<esc>-<home> will work equally well ... another common one - <scroll lock>-<scroll lock>-<ctrl> will work with <scroll lock>-<scroll lock>-<esc>.
Bizarrely though, although without exception every keystroke type kvm has had an alternative, never once have I seen it documented in the supplied manual. (Manual usually = small slip of paper about the size of a postage stamp with Korean or mandarin Chinese which has been translated by a baboon).
I gave up on keystroke KVM's a while back in favour of manual switch types which are a little less convenient, but don't cause any of the issues of inadvertantly switching screens while holding down a CTRL key using GiMP for example, and have the kvm start to cycle - jeez, that's annoying.
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