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  • Re: How to recover when monitor goes blank.

    From David Christensen@21:1/5 to Ram Ramesh on Thu Jun 20 07:20:01 2024
    On 6/19/24 13:45, Ram Ramesh wrote:
    Hi,

      I have my monitor, keyboard and mouse shared through a KVM switch.
    One host is Linux Debian bookworm 12.5 and another is laptop running
    Windows 11. When I leave KVM on the laptop side for extended period I
    have issues switching back to Debian side. When I switch, the screen is
    blank and KB does not respond as if Debian is running headless. I had to remote login and reboot Debian side with KVM locked on this side to get
    back the monitor/KB. This happens regardless of whether I am in Xorg or
    VT.  I do not know how to force Debian/Linux to check for monitor/KB
    again after extended period of disconnect when it has assumed it is
    running headless. Any solutions?

    Regards
    Ramesh


    My Debian machines have Xfce. I configure Applications Menu -> Settings
    Power Manager -> Display -> Display power management -> Off.


    David

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  • From Felix Miata@21:1/5 to All on Thu Jun 20 22:10:01 2024
    Ram Ramesh composed on 2024-06-19 15:45 (UTC-0500):

      I have my monitor, keyboard and mouse shared through a KVM switch.
    One host is Linux Debian bookworm 12.5 and another is laptop running
    Windows 11. When I leave KVM on the laptop side for extended period I
    have issues switching back to Debian side. When I switch, the screen is
    blank and KB does not respond as if Debian is running headless. I had to remote login and reboot Debian side with KVM locked on this side to get
    back the monitor/KB. This happens regardless of whether I am in Xorg or
    VT.  I do not know how to force Debian/Linux to check for monitor/KB
    again after extended period of disconnect when it has assumed it is
    running headless. Any solutions?

    Not to recover, but to perhaps prevent, via kernel cmdline, one can direct the kernel which framebuffer mode to force-enable with video=, e.g.:

    video=2560x1440@60e

    https://www.kernel.org/doc/Documentation/fb/modedb.txt
    --
    Evolution as taught in public schools is, like religion,
    based on faith, not based on science.

    Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

    Felix Miata

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  • From Felix Miata@21:1/5 to All on Fri Jun 21 02:50:01 2024
    Ram Ramesh composed on 2024-06-20 17:43 (UTC-0500):

    Not to recover, but to perhaps prevent, via kernel cmdline, one can direct the
    kernel which framebuffer mode to force-enable with video=, e.g.:

    video=2560x1440@60e

    https://www.kernel.org/doc/Documentation/fb/modedb.txt

    I think kernel thinks that no monitor is attached or KB is present. I
    want to remote login and tell it to look again and find them.
    It appears like there is no magic incantation exists for that. I was
    hoping a write to /sys or /proc file will do the trick, but no such
    thing seem to exists.

    Did you try 'e' as I suggested, or read that page? From there:

    [quote]
    'e' will force the display to be enabled, i.e. it will override the detection if a display is connected.
    [/quote]

    The way I read it, if it doesn't work, it's yet another kernel bug, because it should - prevent - not fix.
    --
    Evolution as taught in public schools is, like religion,
    based on faith, not based on science.

    Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

    Felix Miata

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  • From Felix Miata@21:1/5 to All on Fri Jun 21 05:40:02 2024
    Ram Ramesh composed on 2024-06-20 22:58 (UTC-0400):

    Did you try 'e' as I suggested, or read that page? From there:

    [quote]
    'e' will force the display to be enabled, i.e. it will override the detection
    if a display is connected.
    [/quote]

    Ok, I will try it, but that is a reboot. I guess if I booted with that switch, it will always be on and I would not reach a point of blank
    screen. Make sense.

    I just do not like forcing resolution, but better than broken display.

    The foibles of life complicated by a KVM switch. :p I hope it does what it claims.

    If not, I suppose you could connect both Debian PC and laptop to display at the same time, and use the display's input switch instead of the KVM for video out. --
    Evolution as taught in public schools is, like religion,
    based on faith, not based on science.

    Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

    Felix Miata

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