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Black Screen/Blinking Cursor on Ubuntu Start

PostPosted: 14. May 2021, 21:09
by AkiraRagnas
Terribly sorry to ask this question again, but I've tried every solution I've found and nothing works. Ubuntu 20.04 LTS on a Windows 10 Home host. Latest VirtualBox as far as I know (6.1.22 r144080).

I get the Ubuntu splash screen (black with the Ubuntu logo rotating), then a quick flash of logs, then either a black screen or a black screen with a blinking cursor that takes no input. I'm able to use Ctrl+Alt+F<num> to switch TTY sessions and login. Two observations I've made are that I don't appear to be connected to a network if I login that way, and that it will randomly kick me back to the blinking cursor screen (also accessible through Ctrl+Alt+F1). It doesn't kill the other session though, so I can easily switch back to it, but I thought that was strange.

Virtualization appears to be on in the BIOS and I don't appear to have Hyper-V enabled.

One person suggested uninstalling Guest Additions, so I did, and that didn't help. I've attached the most recent VBox logs. Thank you very much for your help.

Re: Black Screen/Blinking Cursor on Ubuntu Start

PostPosted: 14. May 2021, 23:04
by scottgus1
No Hyper-V on the host, and the VM seems to run OK. Processors are set to 4, same as the physical cores on the host. RAM is 4GB, host had 4.4GB free. Host may starving for CPU & RAM. Try reducing to 2 processors and 2 GB RAM.

Ubuntu is known to go blackscreen and not be able to launch the desktop if the disk fills up. If you were running Ubuntu updates before this happened, that might be your problem. Web-search how to check disk space free in the text terminal of the VM and how to delete things if necessary.

Also make a new Ubuntu VM, 2 processors and 2 GB RAM, and a fresh install of the OS. See if it boots properly. This will check if Virtualbox itself is working.

Re: Black Screen/Blinking Cursor on Ubuntu Start

PostPosted: 15. May 2021, 00:23
by fth0
scottgus1 wrote:how to check disk space free in the text terminal

df -h will do (disk free, human readable). But I'd assume that the 50 GB VDI file is more than enough. ;)

Re: Black Screen/Blinking Cursor on Ubuntu Start

PostPosted: 15. May 2021, 01:39
by AkiraRagnas
Thank you for your help!

Indeed, /dev/sda1 has a size of 43G, with 28G used and 14G available.

Dropping processors and RAM didn't solve it either, going to attempt making a second VM now.

Re: Black Screen/Blinking Cursor on Ubuntu Start

PostPosted: 15. May 2021, 02:46
by AkiraRagnas
Creating a fresh VM for 20.04 LTS appears to have worked; I can log in and everything. How frustrating. Is there an easy way of getting the data off of the old image?

Re: Black Screen/Blinking Cursor on Ubuntu Start

PostPosted: 15. May 2021, 03:09
by scottgus1
Thanks for the command, fth0!

Akira, good that a new VM works. It appears that the problem lies inside the bad VM's OS, not in Virtualbox, though a comparison of logs between good and bad VMs might show a trouble point.

If you care to abandon the old VM and use the new one, you can add the old VM's disk to the new VM's disk controller while they are both shut down. Then start the new VM and mount the old VM's disk using Ubuntu methods. You will then be able to copy file off the old disk to the new disk.

Re: Black Screen/Blinking Cursor on Ubuntu Start

PostPosted: 15. May 2021, 20:54
by AkiraRagnas
Yeah, bit annoying, but that's computers; thank you again for all your help.