Black screen áfter boot (VB 4.3.20)

[Medison]

VirtualBox: 4.3.20

Host: Windows 7 sp1 (x64)
Intel i5-4200M (dual core with HyperThreading @ 2.50GHz)
8GB RAM

Guest: BuildBox - Ubuntu 14.04.1 (x64)
1 core
2GB RAM
12MB VRAM

I am using VirtualBox 4.3.20 with a guest running Ubuntu 14.04.1 (64 bit) on my Win 7 system which I use to build images for my intel Edison and all was working fine. Right before the holidays I fiddled around with the USB settings a bit and since then it has given me a black screen after every boot. Even after removing all the USB devices. I can still access the terminal by pressing [Host+F1] and tried re-installing "virtualbox-guest-dkms" to no avail.
I made a second Ubuntu 14.04.1 (64 bit) guest and that one boots to the desktop as normal, so I think it's safe to say that its not the host system. I realize that some people have issues with the USB settings on windows hosts but so far I haven't come across this problem.
If there isn't a solution to this problem would it be possible to rescue the data from the guest system?

[loukingjr]

If you can't recover your broken Ubuntu guest you could attach its .vdi to your working guest as a secondary hard drive and copy the data over.

[Medison]

If you can't recover your broken Ubuntu guest you could attach its .vdi to your working guest as a secondary hard drive and copy the data over.

Didn't think about that, thanks

[loukingjr]

no problem

[Wyckham]

Can anybody please tell me how to "attach the other machine's virtual drive" to a virtual machine? I know how to add an additional .vdi hard drive in the Storage section of setup, but then how do I enable a running Lubuntu system to "see" that other drive? I've tried many versions of the "mount" command, but nothing seems to work, maybe because I don't know what the fstype is for the -t parameter in the mount command? Also, does the other virtual machine have to be running?

[loukingjr]

You can't add a second drive to a guest while it is running. Also your question has nothing to do with this topic.

[Wyckham]

Sorry, this looked like a good place because the proposed solution was to "attach its .vdi to your working guest". That is what I did [before I started the guest], but the guest cannot see the other virtual machine's .vdi.

[Wyckham]

Got it!

The other drive shows up as sdb; I was trying to mount this using mount /dev/sdb mymountpoint.

It turns out that mount /dev/sdb1 mymountpoint works just fine.



Wyckham

[loukingjr]

Actually if I attach the .vdi from one guest to a second guest it mounts automatically. Even in Lubuntu.