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I have a 1920 x 1200 Dell monitor that I use most often via VGA to servers. When I need a second monitor I have an older Dell 1024 x 768 square monitor... which suffices when needed... but if I connect this monitor via VGA to an already booted Linux system which had booted having the 1920x1200 monitor connected, then I get displayed on the monitor this resolution is not supported.

And vice-versa if the 1024 monitor is connected when booted then I seem to never be able to use the 1920x1200 monitor unless I reboot.

This stinks, is this normal? Is there a fix for this? Why can't I just connect seemingly acceptable monitors over VGA and always have them work? This is with Linux installed as Server with GUI for RHEL-8.10; I assume this happens in all Linux's ?

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  • Yes, normal. Sometimes it works as you intend but only with digital connections. Commented Oct 15 at 20:10
  • This is because video displays weren't intended to be "hot swapped" by manually unplugging/plugging in the cable to a running machine. It's not much of an issue with newer connectors (HDMI, DP) but you'd more than likely short out the old VGA pin-out and damage either your display or your video card. What you 're doing with the manual swap is bypassing the normal negotiation between the video card and the display that occurs at system boot. Commented Oct 19 at 2:42

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I assume this happens in all Linux's ?

I mean, it's been two decades since I connected a screen via VGA (and 1920×1200 is definitely pretty much above what you want to transport in analog), but recognizing a new screen when told to detect it

  1. definitely worked relatively flawlessly back when VGA was still something I used with my Linux systems day-to-day and
  2. still works (I just tried with a USB VGA adapter that I use for other purposes, an 1280-wide old screen that still has a VGA input that I'm never using, and an old 1024-wide projector); I did have to xrandr --auto in between, because the electrical interface on VGA has no good provision to signal "you really need to ask the screen EEPROM for its data again".

(I forget how the equivalent wlroots/wayland tool is called; it exists.)

So, maybe you just need to run xrandr --auto or use your control center's screen dialogue to detect your new screen?

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