Unable to increase resolution of Ubuntu 20.04

[Ross24]

I have a Ubuntu VM install with 1024x768 with no options for higher resolution. The Mac 4k Monitor resolution 3840x2160 is set for 2560x1440 and I would like the set Ubuntu to 1600x900. I have tried xrandr procedures which do not work.

 

[AA5]

Same issue, ran some experiments
TL;DR i can see all resolutions and control it from Ubuntu settings>Displays only if Parallel guest tools are NOT installed!!

seems like display is controlled by Parallel only after installing guest tools, also i can see that the option "More Space" in vm Graphics settings only give one more big resolution but you don't have all resolutions to choose from like the case before installing Parallel Tools!
I am using Ubuntu 20.04.02 LTS
Parallel Desktop Version 16.1.3 (49160)

 

[ChesterF]

Thanks AA5 for pointing out the root problem.
Directions to uninstall Parallels guest tools are here:
https://kb.parallels.com/117044
After following these directions now I have 4K resolution in Ubuntu 20.04

 

[MR RONI]

I can see your windows custom resolution seems to have a pixel clock of 148.5MHz (148500 kHz) but CVT modeline pixel clock is 173Mhz. It may be the monitor can handle the lower pixel clock mode you added in windows but not the higher pixel clock mode you added in Ubuntu. The reduced blanking mode should generate a modeline with a lower pixel clock value.

https://askubuntu.com/questions/1252172/custom-resolution-ubuntu-20-04