Ubuntu 18.04/20.04 LTS on Virtualbox boots up, but black login screen

I'm running Ubuntu Desktop 18.04/20.04 LTS as a guest in Virtualbox on a Windows 10 host with multiple physical screens connected to the host. Every time I boot the Ubuntu VM it comes to a black screen, i.e. no feedback. However, if I type the password and press Enter it logs in and shows the Desktop as normal. I suspect it might be a graphics issue.

Any idea what to do?

Solution 1:

So as i've suspected that it's a graphics issue, I went into the settings, first thinking it's a drivers issue, since many other posters of slightly different questions have had solutions with changing the drivers/controllers (or even CPU architecture etc). The other thought I had that might be the problem is that i'm running multiple screens on the host. Perhaps the guest VM is struggling to connect with them.

What worked for me was to:

• Shutdown the VM
• Go to the specific VM settings
• Go to the Display Tab
• Under the Screen Tab I increased my Monitor Count (which then indicated an error that the "settings are invalid"), which made me think of tinkering with the Video Memory.
• So I increased the Video Memory to 64MB (it was 16MB initially)
• Booted up the VM ... and hey presto it worked ... now i see my login screen

Solution 2:

I did what they said there: Black screen in Ubuntu in Virtual Box "I changed the graphics controller to VBoxVGA"

And it worked for me. My host machine is Windows 10 and it has 2 screens

Solution 3:

With VBox 6.0 and Ubuntu 18.04 neither worked for me.

Switching to VMSVGA fixed the display.