Creating a custom display resolution and making it persistent between Xfce sessions

I am trying to determine why the host Linux OS is freezing while I’m running VirtualBox. The latest attempt is restoring the default display resolution for the host OS to 1920x1080.

I am able to successfully enlarge the VBox display resolution for both Plasma VBoxes (Cooker and Rolling), but have been unable to get the same (custom) resolution it’s using, for the Xfce Vboxes (also Cooker and Rolling) to persist between sessions.

I found directions on these two pages (which apply to Ubuntu - which is not the host OS):

After installing and running the cvt command for the display resolution, the first two xrandr commands on each page, will add the resolution, 1680x931, which is what the OpenMandriva Plasma VBoxes now use and can select it in the Xfce Display setting, but the steps to make it persistent between Xfce sessions isn’t working. Once logging out of Xfce and back in, the display goes back to 1440x900. At this resolution, the screen takes up maybe the middle 75-80% of the screen, but if Plasma can natively accept 1680x931, I don’t see why Xfce isn’t. The VirtualBoxes are using the same GPU (VMSVGA (VMware)). Increasing/decreasing the amount of video memory for the VBox does not affect the display resolution.

The prior display resolution for the host when the OS was freezing, was 1680x1050, in which the 1440x900 resolution in the VBox took up more of the screen.

Thanks in advance for any suggestions.

xrandr --newmode "1600x931_60.00"  123.25  1600 1696 1864 2128  931 934 944 966 -hsync +vsync
xrandr --addmode Virtual1 1600x931_60.00
xrandr --output Virtual1 --mode 1600x931_60.00

These are the commands that would set the desired display resolution. However, I tried adding these to the Xfce Autostart as three separate commands. Once saved and the session restarted (logout/login), the second comnand was listed first, the third command listed second and the first command listed third.

I then tried using them as all one command, which didn’t work.

xrandr --newmode "1600x931_60.00" 123.25 1600 1696 1864 2128 931 934 944 966 -hsync +vsync ; xrandr --addmode Virtual1 1600x931_60.00 ; xrandr --output Virtual1 --mode 1600x931_60.00

Then tried the same command, except removed the semi-colons and the other two xrandr commands, which also didn’t work.

xrandr --newmode "1600x931_60.00" 123.25 1600 1696 1864 2128 931 934 944 966 -hsync +vsync --addmode Virtual1 1600x931_60.00 --output Virtual1 --mode 1600x931_60.00

Is what I am attempting to do, even possible??

I may have found one cause of the host OS freezing while using VirtualBox. It has nothing to do with the host display resolution. The display would black out and the host OS freeze when on one particular web site using Firefox. A web site for a local TV channel, it has too many videos on it and seems to be too much for VirtualBox to handle.