Problem Description:
When booting the Ubuntu 24.04.2 ISO in a new virt-manager/libvirt/QEMU/KVM VM, it usually (but not always) boots to a black screen with only a X mouse cursor. This can also occur after logging out the live session user and trying to log back in.
In this state, sometimes the system is responsive to pressing the virtual power button for a clean shutdown, and sometimes it is not. The system does respond to sending keystrokes Ctrl-Alt-F1/Ctrl-Alt-F2/etc, but these give either another similar black screen with either X or arrow mouse cursor, or a blank screen with only a flashing terminal cursor.
How to avoid getting these stuck black screens in the live environment? Is there any specific required VM setting(s) to avoid this?
Relevant System Information:
Host system is Xubuntu 22.04, with virt-manager/libvirt/QEMU/KVM all installed from standard Ubuntu repositories. The guest is booting this Ubuntu 24.04.2 ISO:
The guest does not have an internet connection (the virtual internet connection cable is unplugged). The purpose of this ephemeral guest system is to test stuff in the Ubuntu 24.04 live CD environment, so there is no installation on the guest, not even a virtual hard disk.
Screenshots or Error Messages:
What I’ve Tried:
Changing the Video device between QXL and Virtio. The issue might be occurring less with the Virtio video device, but not sure, and in any case it’s not a complete fix.
Setting up and enabling 3D acceleration for the VM. Although it did boot correctly the one time I tried this, there were other rendering issues, so would like to be able to get this working without 3D acceleration.
Resizing the VM window to be bigger + using Virtio video device. Not sure if this might have had some positive effect? But doesn’t seem to be a complete fix either.
Adding nomodeset to the boot parameters. This seems to always boot to black screen.
@halogen2 Quite a discovery, it prompted me to have a play.
Virtual Machine Manager with Qemu/kvm Ubuntu 24.04 host and Ubuntu 24.04.2 ISO guest (no storage i.e. live session)
VM booted 4 times out of 5
Live user log out/log in failed every time
Power off did not shut down cleanly and VM would not reboot
Screenshot below is the message after power off
+1 here System: Fedora 41 kernel 6.13.8 and libvirt 10.6.0-7 Behavior: Both Ubuntu Desktop 24.04.1 and 24.04.2 with valid checksums do not display. 24.10 works
They will play the start up sound, then a black screen with a moveable mouse cursor that is literally an X.
Extra troubleshooting:
I have tried Spice Display with QXL and Virtio Video types without openGL acceleration.
Booting the ISO with Safe Graphics mode has the same behavior.
Switching to TTY doesnt work either. TTY will display the login for a tenth of a second before the screen goes full black.
Decided to try today’s daily build of 24.04 ISO. Looks like this ISO is not getting stuck on this black screen (testing with Virtio video device and disabled 3D acceleration)
However, logging out the live session user still leads to a black screen with only a mouse cursor. In this state, the system responds to pressing the virtual power button for a clean shutdown.
It’s something only with GNOME (not Plasma 6 nor Xfce)
It seems to happen more-frequently on laptop battery vs AC
Seems to only happen with UEFI boot vs Legacy
Happens regardless of Xorg or Wayland (both GNOME session itself and WaylandEnable=False for GDM)
I saw it happen Fedora 38 or 39, it eventually came as an update to openSUSE Tumbleweed, and then Ubuntu (not sure first version but it still happened a week ago 24.10).
To workaround Fedora 42 removing GNOME on Xorg support, someone suggested switching to TTY from log-in and then startx. I’m thinking that might also workaround that if it’s GDM causing the issue!
