Ubuntu 18.04.1 running on VirtualBox 6.1.2 and 6.1.4 in Windows 10 logs me out and closes all my win

[microajim]

Full title: Ubuntu 18.04.1 running on VirtualBox 6.1.2 and 6.1.4 in Windows 10 logs me out and closes all my windows

Cross-posted from askubuntu dot com/questions/1215070/ubuntu-18-04-1-running-on-virtualbox-6-1-2-and-6-1-4-in-windows-10-logs-me-out-a

On Mar 2, 2020, I tried booting my Ubuntu 18.04.1 VM (VirtualMachine) for the first time since Feb 13, and found that it was unstable. Actually, I first found it locked up. I got a blank purple screen. I deleted my whole VHD (Virtual Hard Drive) and restored it from my backup of Feb 13, my Ubuntu_18.04.1 folder containing my VHD, Ubuntu_18.04.1-2.vdi. Then I got a login screen and got in. However, it soon locked up. I was using VirtualBox ver 6.1.2-135663. It's on Windows 10.
VirtualBox version 6.1.4 was available, so I upgraded to version 6.1.4-136177. Then after booting my VM, it was unstable. It would show a mis-coloured pixel or two and lock up briefly after I opened a terminal window and moved it. Desktop background and icons disappeared. They reappeared and then I could move the terminal window again. But then it logged out and when I logged back in, my terminal window was closed. That's no good. It's a sick puppy.
I'm using a 20 GB dynamically-allocated VHD, up to ~12,900,000 kB as of Feb 13.

I tried changing the display adapter in VB (VirtualBox) back and forth, and also changing the Linux display manager from gdm3 to lightdm, but it didn't help. Googling, I didn't find any other complaint about this problem here on the VirtualBox forums, but there are a few other related complaints that I can look at on AskUbuntu in the meantime.
I have a native install of Ubuntu 18.04.1 on a separate PC, and it's solid. I tend to suspect VirtualBox, but why would ver 6.1.2 suddenly go funny on me?
Maybe a Windows 10 automatic update?

Any ideas?

[scottgus1]

I tried changing the display adapter

Please undo everything from the above point onward, then zip and post a guest vbox.log, using the forum's Upload Attachment tab.

BTW, VHD is a format of virtual drive file. You might not want to call your .vdi a VHD, it will confuse forum users who try to help. Calling it a vdi is more understandable. If you ever actually have a .vhd file, those can be called VHD with no loss of understanding.

[microajim]

Full title: Ubuntu 18.04.1 running on VirtualBox 6.1.2 and 6.1.4 in Windows 10 logs me out and closes all my windows
@scottgus1: Thanks for the suggestion.
Attached: VBoxLogs.zip 147 kB
File comment: VirtualBox logs for locked-up Ubuntu 18.04.1 install

I had reverted to my original display adapter, VBoxSVGA, in the Graphics
Controller drop-down box in VB Display Settings, back on Mar 3.

Today, Mar 6, 2020, I did Ctrl-Alt-F2 at the lightdm login screen and did:
sudo -s to become root, then
apt-get remove lightdm
apt-get install gdm3
It installed and gave me my gdm3 login.
Then I took a break, and after that, it was back to the lightdm login screen.
I did: Ctrl-Alt-F2
apt-get remove lightdm
It was not found installed.
I did Ctrl-Alt-F7 and logged in. Then it was not logging in; and it has been
stuck at an almost-blank small black screen in a white background in VB for the
last ~10 mins.
I'm uploading the logs.
...it's still locked up; I may have to just reinstall. I keep important data in
a shared folder in my host Windows so I won't lose anything.
Thanks for any assistance.

[scottgus1]

Your log contains these lines:

{timestamp} HM: HMR3Init: Attempting fall back to NEM: VT-x is not available
{timestamp} NEM: WHvCapabilityCodeHypervisorPresent is TRUE, so this might work...

You might notice in the guest window's Status Bar the green turtle: The choice of animal is appropriate: Your guest is running, just really slow. This is because a service that uses Microsoft Hyper-V is running on your host PC. Normally Hyper-V blocks Virtualbox. But your PC is of the type and OS where Virtualbox can attempt to run the guest using the Hyper-V engine. This arrangement is still being developed and isn't 100% yet.

If VirtualBox is running without Hyper-V enabled, and nothing else is interfering with hardware virtualization (VT-x / AMD-V), then the usual virtualization icon () will be seen in the Status Bar.

To turn Hyper-V off completely, do this:

1. Shut down all programs. You will have to reboot your host.

2. Look into the 64-bits tutorial, 2nd post, points 2 & 3 and ensure that none of these things are running.

3. Find the Command Prompt icon, right click it and choose Run As Administrator.

4. Enter this command:

bcdedit /set hypervisorlaunchtype off

5. Enter this command:

shutdown -s -t 2

6. When the computer turns off, unplug it for 20 seconds. Then plug it in again and boot up Windows 10.

Your Virtualbox should be running now. If the green turtle still appears and the tell-tale lines are in the log, try all the steps again. If you don't get the standard virtualization icon, post back exactly what you did and we'll try to help some more.

For further info, see I have a 64bit host, but can't install 64bit guests and https://www.tenforums.com/tutorials/139 ... puter.html