Ubuntu guest halts with black screen during boot

[dr strange]

Hi,
I had a ubuntu guest (ubuntu-20.04.3-desktop-amd64) on windows 10 host on VB 6.1.26. I used it well for some time but after a few months I couldn't start ubuntu. It stucks with black screen during the boot. I updated the VB to 6.1.32, but the outcome was the same. I really appreciate if anyone can help with it. You can refer to the log file in attachment.

[mpack]

The log is incomplete. Make sure VirtualBox is closed down before grabbing the log (if the error dialog is still visible then VirtaulBox is still running).

Zip the log file then attach the zip.

[dr strange]

Hi,
Thanks for reply. Please find the updated log file in the attachment.

[mpack]

Your Ubuntu hard drive capacity is only 10GB, why so small? Assuming that this also includes a swap partition for the 4GB RAM allocation then that implies a very small usable disk size. Black screen on boot has been reported several times previously when an Ubuntu main disk partition is too small. The disk needs to be increased in size: I always find 32GB to be a good number.

Also requiring attention is your over-allocation of resources:

// Available to share between host and guest
00:00:03.161997 Host RAM: 16221MB (15.8GB) total, 4809MB (4.6GB) available
00:00:04.271816 CPUM: Physical host cores: 4
...
// How you actually shared available resources
00:00:03.338759 RamSize <integer> = 0x0000000114d00000 (4 644 143 104, 4 429 MB, 4.3 GB)
00:00:03.338940 VRamSize <integer> = 0x0000000008000000 (134 217 728, 128 MB)
00:00:03.338756 NumCPUs <integer> = 0x0000000000000004 (4)

Something on the host is consuming excessive RAM. While that remains the case you certainly can't afford to give everything left to a VM. You either need to eliminate the host OS memory hogs before launching a VM, or reduce the RAM allocation to the VM. You should reduce the CPU allocation to 2 cores.

[dr strange]

Hi,
Thanks for reply.
I decreased the RAM and the number of CPU cores, as you suggested. It didn't work. In addition, I also increased the size of the virtual disk from 10 to 15 GB. That also didn't help. Now it halts during the boot with Ubuntu logo with black background.
Please refer to the updated logs.
Thanks.

[scottgus1]

I also increased the size of the virtual disk from 10 to 15 GB. That also didn't help

There's one more step, increase the partition size inside the VM's OS: How to Resize a Drive

With 3D acceleration you'll want maximum video RAM.

[mpack]

I decreased the RAM and the number of CPU cores, as you suggested. It didn't work.

Did not work in what respect? The notes regarding RAM and CPU over committment were clearly labelled "also requiring attention". They were not a fix for your black screen.

In addition, I also increased the size of the virtual disk from 10 to 15 GB. That also didn't help.

The suggested figure was 32GB, which I regard as a minimum. And as usual it also needs to be followed by running a partition manager in the VM (e.g. boot from a GParted ISO).