Ubuntu guest not booting correctly, (mostly) solid blue screen (used to work fine) (Win10 host)

[rpgtiger]

My Ubuntu VirtualBox guest has stopped booting within the last few days. It seems to go through most of the boot process, but once complete it seems to mostly only be able to show a solid blue screen. The only thing I can do is force power off.

I have a few screencaps I took of what happens during the booting process, but I apparently can't directly link to them at the moment because this is a new account, so you'll have to go imgur dot com /a/AtZWv to have a look.

Image 1: Does this pretty soon after bootup. The "orphaned inodes" thing seems to happen after improper shutdown, though since I cannot shut down normally I don't have much of a choice. Normally I do a proper shutdown.

Image 2: It then shows the normal Ubuntu boot screen. I just pulled the image from Google images since I couldn't screengrab it in time, but I wanted to show exactly what it did.

Image 3: Not long after, it just shows this. Solid blue screen, doesn't respond to anything.

Image 4: During the process of writing this post, I switched back to the tab and noticed that a login prompt was flickering in and out, popping up for a fraction of a second before disappearing for a second or so. I was actually able to type my login credentials into it, however once I submitted them it remained frozen on the blue screen again. Still doesn't respond to ACPI shutdown.

The only thing I could find on this after a bit of searching (unfortunately using "blue screen" as a search term mostly finds issues related to Windows BSODs) was something about too much RAM allocated to the guest and not enough left for the host, but I don't think that should be an issue, I've only assigned 2GB of my 8GB of total RAM to the VM, and Windows task manager isn't indicating a memory shortage. Not to mention it's worked fine under similar conditions before - It's only stopped working within the last day or so. What should I look into next?

[socratis]

It's only stopped working within the last day or so.

What happened between it working and not? Host updates? Guest updates? VirtualBox updates?

Host version: ...
Guest version: ...
VirtualBox version: ...

With the VM shut down completely (not paused or saved), right-click on the VirtualBox Manager and select "Show Log". Save the "VBox.log" (just the first one), ZIP it and attach it in your response (see the "Upload attachment" tab below the reply form).

PS. You do not have to attach a blue screen. We kind of suspect what it looks like

[rpgtiger]

Host version: Windows 10 64-bit, Release 10.0.14393
Guest version: (Not really sure where to find this... The only version I could see in the VM's settings just said "Ubuntu (64-bit)" and any sort of version number wasn't readily apparent in the log)
VirtualBox version: 5.1.14 r112924 (Qt5.6.2)

The log is attached.

PS. You do not have to attach a blue screen. We kind of suspect what it looks like

Hey, you never know what might be useful... I try to be thorough when describing a troubleshooting problem.

[socratis]

00:00:06.086507   VRamSize         <integer> = 0x0000000001000000 (16 777 216, 16 MB)

The amount of display RAM seems way too low. I'd take it to at least 64 MB, if not 128 MB since you also have 3D enabled. If that doesn't work, try to disable 3D, maybe there's a bug in the latest Ubuntu update?

00:00:21.775826 VMMDev: Guest Additions information report: Version 5.0.18 r106667 '5.0.18_Ubuntu'

Not only you have an older version of the Guest Additions, but you have the ones from the Ubuntu distribution, which is a fork of the VirtualBox ones.

A couple of notes:

• You should be able to note next time your Ubuntu's guest version. It could really help if there was a known bug with a specific Ubuntu version.
• Just for the record, you had plenty of RAM available on your host at launch time. 4GB to be exact.
• You were so thorough in your description that's why I said that the screenschots were (almost) not needed. Especially the blue one

[rpgtiger]

Sorry for the delayed response, I've been busy for the last few days. Anyway, I upped the video memory to 128 MB and turned off 3D acceleration, and still no dice. Furthermore, this time I saw this error box flickering in and out once it reached the blue screen: http://imgur.com/LFTqLMh

I looked into the Guest Additions, and the Vbox manual page on them says they are to be installed inside the VM after creation, so I don't think I'd be able to update them until I can successfully boot it again.

New log is attached, and Ubuntu version is 16.04.1

[socratis]

I don't think I'd be able to update them until I can successfully boot it again.

Boot into safe mode and do it. There's no point in trying to troubleshoot a graphics problem by installing the GAs, when the graphics problem prevents you from installing the GAs. Boot into safe mode, uninstall the old ones (purge actually is a better word) and install the official, matching GAs.

[rpgtiger]

So I was having a lot of trouble with Ubuntu's recovery mode, namely that failsafe graphics mode brought up a blank "What do you want to do?" prompt and wouldn't seem to do much of anything else, and when I dropped to root shell prompt I couldn't seem to get anything to mount, much less the guest additions ISO, leaving me with nothing but an empty root folder. I eventually just gave in and deleted and reinstalled the entire VM from scratch. I've installed the guest additions this time, so hopefully that keeps everything in working order, but otherwise I'll let you know.

Honestly I'm kind of frustrated I wasn't really able to get anywhere with troubleshooting this. I'm a computer science student that's been meaning to try and get into working with Linux, and I'm disappointed that I couldn't at least partially figure this out even with a good deal of Googling. I'll probably get better at it with some more time and experience, or at least so I hope. Anyway, thanks for the help, and sorry that this all ended up a bit of a waste of time.

[socratis]

I'm a computer science student

I honestly hope for your own sake that you're a freshman
Sorry man, I couldn't resist...

sorry that this all ended up a bit of a waste of time.

Au contraire!
You've learned a lot of stuff. Learning is never, ever a waste of time. I used to be both a student and later on a TA, and I've seen frustration from both sides of the fence. That's a good feeling to have. Indifference is the bad one.