Start up the VM and hopefully it won’t hang. You can read about the differences between the settings here. If it’s already at VBoxSVGA try VMSVGA instead.

Most likely your graphics controller will be VMSVGA if you are running a newer version of Linux. Do this by opening up the settings for your VM and select Display. If it does not boot, which it didn’t for me, you can change the VirtualBox graphics controller. Shut down and restart the VM and see what happens. Now try to re-install the VirtualBox Guest Additions. This means you will get a 800 x 600 screen that can’t be resized. Just choose resume to continue booting in safe mode which will hopefully show the login screen but with the VirtualBox Guest Additions graphic drivers disabled. You won’t be able to run any of the diagnostics because VirtualBox can’t remount the file systems as read only.

If you don’t know to boot into safe mode in Ubuntu hold down the left-shift key. The first step in trying to fix this problem is to boot in safe mode. I also installed updates on my Windows 8.1 host (I know, I need to upgrade to Windows 10, it’s on the list) but I don’t think that had anything to do with the problem. The problem occurred after upgraded the Ubuntu 18.04 guest to kernel 4.15.0-52. It will either stay purple but sometimes goes black. The problem is my Ubuntu VM boots but freezes before getting to the login screen. This is the second time so I better write down what I did so I hopefully remember if it happens a third time. This issue happened to me many moons ago when I first upgraded to VirtualBox 6 and Ubuntu 18.

Some notes so I remember how to fix this problem if it happens again and I don’t waste a bunch of time figuring it out right before a customer production release.

Is virtualbox safe