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nobody special
Asked: 2024-11-13 22:14:18 +0800 CST

Kubuntu 24.10 Login screen flashing on and off, mostly off for longer periods

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Since upgrading to 24.10 my login screen is flashing on and off, though mostly off for long periods of time, and when it's on it's barely ever as long as a second.

Sometimes I get a message on my black screen saying out of range.

I can still login by typing my password as thankfully focus defaults to the password input box, and once I get to the desktop things are fine.

Any ideas how I can stabilize my login manager or is this a known un-fixable bug atm?

kubuntu

1 Answers

  1. Best Answer

    So this is my final solution though I don't want it to be because I feel it could be overwritten by any system updates to the sddm package or related boot process.

    I have spent the past two days trying to find a better solution but nothing seems to work.

    My solution is to override the resolution and refresh rate for the monitor in the sddm config as suggested by @Saxtheowl, which I did by overriding the DisplayCommand using xrandr in /etc/sddm.conf.d/sddm.conf.

    But this is where I feel my solution could be overwritten by a system update as it is a system installed file.

    So I looked for a user friendly way of making local changes but nothing seems to work.

    I found a manjaro forum post https://forum.manjaro.org/t/sddm-is-not-respecting-resolution/145706/5 where it was suggested to place the DisplayCommand override in /etc/sddm.conf.d/00-display-command.conf

    But that file does not work so assuming they were on to something and knowing so many other applications on linux use a config directory for local config changes I referred to the sddm source which specifically says

        void ConfigBase::load()
    {
        //order of priority from least influence to most influence, is
        // * m_sysConfigDir (system settings /usr/lib/sddm/sddm.conf.d/) in alphabetical order
        // * m_configDir (user settings in /etc/sddm.conf.d/) in alphabetical order
        // * m_path (classic fallback /etc/sddm.conf)

    On my kubuntu system m_sysConfigDir does not exist, so I have to assume that m_configDir is the one that is used and that does appear to be true as modifying the DisplayCommand in sddm.conf in that directory does indeed change the sddm greeter.

    The sddm ConfigReader.cpp seems to load all files within m_configDir into a list then extract the config directives from the files in the listed order of the files, so it would appear that the directives found in the later alphabetically sorted file list would be the final directives to be used for configuring sddm but it just doesn't work for me.

    I tried the suggested 00-display-command.conf and sddm_user_override.conf but neither file worked, so as I do not have the time to compile a local copy of sddm to go through extensive debugging to work out what it does, I have no choice but to override the default DisplayCommand in /etc/sddm.conf.d/sddm.conf

    • DisplayCommand=/usr/share/sddm/scripts/Xsetup

    with

    • DisplayCommand=xrandr --output DP-2 --mode 2560x1440 --rate 143.86 --primary --output DP-0 --mode 1920x1080 --rate 144.00 --right-of DP-2

    And hope it does not get overwritten in a system update.

    My rudimentary understanding of shell syntax suggests all /usr/share/sddm/scripts/Xsetup does is try to find your displays using xrandr and order their position and maybe do something with the resolution, but as I'm doing it all manually with xrandr it should be okay to bypass it and my system certainly boots to the greeter with no issues now.

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