Ubuntu 20.04 stuck on black screen after boot and login

[eieieiei]

Hello!
Up until the previous time I booted up this VM, I had no problems running it.
However, now my Ubuntu 20.04 VM gets stuck at a black screen after the Vbox and Ubuntu logo screens.
But I can see and move the mouse cursor.
I'm not sure what changed that caused this to start happening. Is there something that can be done to fix it?

The log is attached.
I see someone have the same problem,but I'm not lucky enough to solve the problem QAQ.

VBoxUI.zip

(1.65 KiB) Downloaded 2 times

VBox.zip

(22.93 KiB) Downloaded 5 times

Virtualbox version is 6.1.32 r149290

[mpack]

00:00:08.061600 Host RAM: 15741MB (15.3GB) total, 4669MB (4.5GB) available
...
00:00:08.345539 RamSize <integer> = 0x0000000100000000 (4 294 967 296, 4 096 MB, 4.0 GB)
00:00:08.346108 VRamSize <integer> = 0x0000000010000000 (268 435 456, 256 MB)

That is dangerously close to exhausting available RAM. For a 16GB host to only have 4GB available, something must be hogging a lot of RAM. I would find out what that is and reduce or eliminate it. The alternative is to reduce the allocation to the VM, say to 2GB.

00:00:07.860699 VirtualBox VM 6.1.32 r149290 win.amd64 (Jan 17 2022 11:29:30) release log
...
00:00:24.244724 VMMDev: Guest Additions information report: Version 6.0.0 r127566 '6.0.0'
00:00:24.244834 VMMDev: Guest Additions information report: Interface = 0x00010004 osType = 0x00053100 (Linux >= 2.6, 64-bit)
00:00:24.245106 VMMDev: Guest Additions capability report: (0x0 -> 0x0) seamless: no, hostWindowMapping: no, graphics: no

Having those ancient GAs probably doesn't help either.

00:00:10.109639 CPUM: Physical host cores: 6
...
00:00:08.345533 NumCPUs <integer> = 0x0000000000000006 (6)

Nor does allocating all of the host's CPU cores to the VM, leaving none for the host OS and apps (which includes VirtualBox). I really don't understand why people keep doing this. Give the VM two cores, leave it at that until it becomes obvious that more are needed: and remember that extra cores usually just sit idle, they do not make the VM faster, in fact there's an overhead for managing them.

[scottgus1]

The log was taken while the VM window was still open. It's better to get the VM window closed before taking the log, so we can get a complete log.

The VM 'hardware' doesn't show any operating problems to me, aside from the config issues Mpack pointed out.

Ubuntu is known to go blackscreen if there is not enough free disk space to start the desktop environment. This happens in real PCs too. The solution is to log on text-only and delete stuff until the desktop environment can start. Web-search how to fix this in an Ubuntu PC and apply the steps to the VM. Also see How to Resize a Drive