Login screen is blank

[moon82]

I have an Ubuntu 16.04 guest running on a Windows 7 host. I've been using this guest for a long time, but today I updated it with sudo apt update && sudo apt upgrade. Now I cannot log into it any more; the login screen is black. I don't have 3D acceleration enabled.

I cannot start a terminal with right-ctrl-F1 (is that supposed to work?) and I don't know what else to try. Log is attached. Thanks!

[socratis]

00:00:00.918689 NumCPUs <integer> = 0x0000000000000004 (4)
00:00:01.409050 CPUM: Physical host cores: 4
00:00:01.671869 Full Name: "Intel(R) Core(TM) i7-4900MQ CPU @ 2.80GHz"

You have assigned all your CPUs to the VM. The host is going to run low on resources, since VirtualBox cares about physical processors (cores), not logical ones (threads). See "CPU Cores versus threads" and "Why is it a bad idea to allocate as many VCPUs as there are physical CPUs?". And yes, your i7-4900MQ has 4 cores...

00:00:00.918902 [/Devices/usb-ehci/0/Config/] (level 4)
00:00:00.918915 [/Devices/usb-ohci/0/Config/] (level 4)

Your guest supports USB3, you might want to take advantage of that...

00:00:00.918932 VRamSize <integer> = 0x0000000001000000 (16 777 216, 16 MB)

That's definitely low for your guest, you should take it to 32, 64 or even 128 MB. That's peanuts compared to the 8192 MB that you've allocated for your RAM...

00:00:01.554371 [/USB/HidMouse/0/Config/] (level 4)

That part is missing from your log. Are you using a PS/2 simulated mouse? You could switch to USB tablet...

00:00:01.427331 Host path 'C:\', map name 'C_DRIVE', writable, automount=true, create_symlinks=false, missing=false

Are you 100% sure that you want to give complete reign to your host's main hard drive? You're not afraid of something going out of whack on your guest (intentionally or not), that could really screw up your host? I'd suggest an isolated area on your host for read-write access. IF you have to...

00:00:07.564248 VMMDev: Guest Additions information report: Version 5.2.6 r120293 '5.2.6'

You're already aware of the fact that you need to update the GAs, and without any GUI access, I guess that's where your question comes in:

I cannot start a terminal with right-ctrl-F1 (is that supposed to work?)

If you have set your HostKey to be RightCtrl, then yes, it should work. But according to your log:

00:00:00.788049 DMI Product Version: ThinkPad T440p

You may have to hold the Fn key down for the F1-F12 keys to work actually as function keys, or something funky like Fn+Esc to lock the keys(?). Give it a shot...

[moon82]

Thanks for the suggestions. Using the Fn key doesn't help. No difference if I reduce the number of CPUs (as I said, I've been using this guest for a long time.)

Got anything else? Or is this hopeless?

[socratis]

I think I gave you a lot more than 2 suggestions... That's all I got.

Oh, I forgot one; restore from backup and try again.