Super quick: xrandr and resolution
You may use IceVM or other skinnier window manager or you just need to set your resolution with your own ways. Xrandr can do just that.
Check out your available modes and outputs
xrandr
You get a list of outputs and modes in the likes of this
Screen 0: minimum 8 x 8, current 7680 x 1464, maximum 16384 x 16384 GPU-0.DP-0 disconnected (normal left inverted right x axis y axis) GPU-0.DP-1 disconnected (normal left inverted right x axis y axis) GPU-0.DP-2 connected primary 2560x1440+2560+24 (normal left inverted right x axis y axis) 597mm x 336mm 2560x1440 59.95*+ 1920x1200 59.88 1920x1080 60.00 59.94 50.00 23.97 60.05 60.00 50.04 1680x1050 59.95 1600x1200 60.00 1280x1024 75.02 60.02 1280x800 59.81 1280x720 60.00 59.94 50.00 1152x864 75.00 1024x768 75.03 60.00 800x600 75.00 60.32 720x576 50.00 50.08 720x480 59.94 60.05 640x480 75.00 59.94 59.93 GPU-0.DP-3 connected 2560x1440+0+0 (normal left inverted right x axis y axis) 597mm x 336mm 2560x1440 59.95*+ 1920x1200 59.88 1920x1080 60.00 59.94 50.00 23.97 60.05 60.00 50.04 1680x1050 59.95 1600x1200 60.00 1280x1024 75.02 60.02 1280x800 59.81 1280x720 60.00 59.94 50.00 1152x864 75.00 1024x768 75.03 60.00 800x600 75.00 60.32 720x576 50.00 50.08 720x480 59.94 60.05 640x480 75.00 59.94 59.93 GPU-1.DP-0 disconnected (normal left inverted right x axis y axis) GPU-1.DP-1 disconnected (normal left inverted right x axis y axis) GPU-1.DP-2 connected 2560x1440+5120+0 (normal left inverted right x axis y axis) 597mm x 336mm 2560x1440 59.95*+ 1920x1200 59.88 1920x1080 60.00 59.94 50.00 23.97 60.05 60.00 50.04 1680x1050 59.95 1600x1200 60.00 1280x1024 75.02 60.02 1280x800 59.81 1280x720 60.00 59.94 50.00 1152x864 75.00 1024x768 75.03 60.00 800x600 75.00 60.32 720x576 50.00 50.08 720x480 59.94 60.05 640x480 75.00 59.94 59.93 GPU-1.DP-3 disconnected (normal left inverted right x axis y axis)
or in virtual environment something like this
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 8192 x 8192 Virtual-0 connected 1024 x 768+0+0 0mm x 0mm 1024x768 59.92 + 1920x1200 59.88 ....
Outputs are the names before each resolution list, such as GPU-0.DP-0, GPU-0.DP-1, GPU-0.DP-2 or Virtual-0, Virtual-1 etc.
Available resolutions are under the outputs. We're interested in the first column.
You can change your single output resolution by typing
xrandr --output <output> --mode <mode>
In the first example this would be like
xrandr --output GPU-0.DP-2 --mode 2560x1440
Or with the virtual guest something like this
xrandr --output Virtual-0 --mode 1920x1200
That's it! Put it in your rc.local or just run it when you start your session.