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List:       openbsd-misc
Subject:    Re: Mouse not working via KVM switch
From:       Karel Lucas <cahlucas () planet ! nl>
Date:       2023-08-21 20:51:41
Message-ID: 9c39bac5-cabd-613c-b799-20648347a325 () planet ! nl
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Dear Nick,

I have now installed Linux on the same computer in place of openBSD and 
the mouse works fine via the KVM switch. This despite possible broken 
capacitors, wrong voltages and malfunctioning computers. Note that not 
all computers connected to the KVM switch will work at the same time. 
There appear to be other problems with openBSD's X-window system. The X 
session on openBSD is started manually with "startx". After stopping 
such a session with ctrl + alt + backspace I get the following error 
messages:

    WARNING: Kernel has no file descriptor comparison support: No such 
file or directory
    (EE) Failed to open authorization file 
"/root/.serverauth.xxxxxxxxxx": Permission denied
                                      (xxxxxxxxxx has different 
characters at each session)
    xterm: fatal IO error 35 (resource temporarily unavailable) or 
KillClient on X server ":0"

I don't know what these error messages mean and how to fix them. Maybe 
someone can help me with that. It looks like it's not just a problem 
with the mouse, but there's more to it.



Op 19-08-2023 om 03:58 schreef Chris Bennett:
> On Fri, Aug 18, 2023 at 07:58:03PM +0200, Karel Lucas wrote:
>> Dear Nick,
>>
>> For more than ten years I have been working with an ATEN brand KVM switch
>> together with several computers, including linux and openBSD (version 
>> 4.1).
>> In all these years I have had no problems, not with my KVM switch, 
>> nor with
>> any degree of disconnection. The keyboard works flawlessly via the 
>> switch,
>> it's only the mouse that I have a problem with, and only with openBSD.
>>
> This is not very clear at all.
> You have used the same KVM switch for ten years, but haven't considered
> it having hardware degradation over that time? Capacitors are well known
> for having limited lifetimes and are *usually* the first item looked at
> in repairs. Switches also fail due to dirty contacts.
>
> Or, are you saying that everything worked fine for OpenBSD 4.1, but not
> for OpenBSD 7.3? The changes over that time have been enormous.
>
>> Op 17-08-2023 om 13:56 schreef Nick Holland:
>>> First of all, does your mouse work directly plugged into the OpenBSD
>>> computer?
>> Yes, it does.
>>> If so, it's your KVM switch.
>> As I mentioned above I have been working with my KVM switch and 
>> openBSD for
>> over ten years with very good results.
>>
>>> Second...if you boot the OpenBSD machine with the KVM pointed at the
>>> OpenBSD machine, does it work?
>> No, even then it won't work.
> Have you swapped ports on the KVM switch to rule out a partial hardware
> failure on the switch?
> Have you also disconnected the other hardware and OS inputs to rule out
> them as the source of the problem?
> Have you checked that the other machines are producing the correct
> supply voltages? Power supply failures are a consistent problem with
> computers. High or low voltages don't mix well.
> Have you checked with your switch manufacturer to make sure there wasn't
> a problem with your switches model? It happens a lot.
>
> After ten years of service, if you insist that the switch isn't the
> problem, (Prove it) then you need to also prove that the other hardware
> is functioning properly. Do not believe what the BIOS or sensors say
> that the voltage is. A bad voltage will cause those readings to fail.
> Get a good voltmeter with excellent probes for this kind of work and
> check *everything*.
> Please use a great deal of care. You will need to measure voltages on
> the motherboards in addition to what the power supply puts out.
> Everything is running and you will need to check in many spots.
> Also, there are high voltages inside the power supply. Don't get
> electrocuted. Drain the voltages off the capacitors in there with a
> suitable tool for that purpose if you go inside there. Yes, even with
> the power off and power cable disconnected.
>
> And it's tricky. I have a power supply cable for two hard drives. Two
> connectors crimped across the same cable. One of the crimps is bad.
> Recognizing that saved me a trip to hell after about an hour. Easy to
> fix, damned hard to locate.
>
> Chris Bennett
>
>
>>> You
>>> might be able to improve how OpenBSD deals with KVM switched mice,
>>> because yes, it does seem to be a little more touchy than some other
>>> OSs, but someone with good programming and HW trouble shooting
>>> skills AND a cheap-*** POS KVM switch would have to care. Most people
>>> that skilled generally just buy a better KVM switch and move on.
>> That more than ten years of loyal service proves that my KVM is of good
>> quality.
>>> What does the dmesg show as you switch the KVM around?  That would tell
>>> us how the KVM works.  Some are equiv. of plugging and unplugging the
>>> mouse/keyboard/monitor, some do some kind of "keep alive" so the
>>> computer thinks the mouse is still there.  Both can cause problems of
>>> different types (my "good" one seems to plug/unplug the mouse/keyboard,
>>> but has a great keep-alive for the monitor).
>> What I've learned about my KVM switch over the past ten years is that 
>> both
>> the mouse and keyboard are emulated when they are switched to another
>> computer. Never have I had any problems with my computers when switching
>> with my KVM switch.
>>
>>
>>


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