I have installed ubuntu 20.04 on virtualbox 6.0.20 and I have installed guest additions.
The issue is that if I resize the screen resolution to whatever size, even to predefined resolutions, it will always start/boot at 800x600 and I have to resize it again.
What I noticed is that when it boots, it goes for ~1 sec to the previous screen size but shows only black and then just before the wallpaper-desktop appears it goes to 800x600.
Any ideas?
I had the same problem with the new Kubuntu release. Do the following:
I'm using VM VirtualBox ver. 6.1.6, Extension Pack (with included Guest additions virtual CD) is also 6.1.6
If someone knows how how to remedy the resolution issue with VMSVGA selected as Graphics Controller, I'd love to read it.
Update #1
This issue with screen resizing didn't let go of me, so I went and searched on the web some more.
From what I've read - and with my limited knowledge of inner workings of Linux systems, hopefully understood it at least somewhat correctly - the problem lies in relation between the graphic drivers included in Oracle's VM VirtualBox Guest Additions and the new Linux kernels that came with the recently released version of Ubuntu distro and others based on it. It seems the drivers present in ver. 6.1.6 Guest Additions aren't working correctly with these new kernels, hence the resizing problem when the Graphics Controller in VM is set to VMSVGA.
So until Oracle comes up with updated version of VirtualBox/Guest Additions, the temporary solution is the one I explained above, or what I've tried earlier and for me at least, works as well.
I chose version 6.1.2 of Guest Additions because there's a bug with Bidirectional Clipboard support in 6.1.4.
It's a bug. Upgrade to 6.1.8, and the problem goes away.