virtualbox.org

Hi, so I have a problem. I was experimenting with Virtual Box for the first time, and when I was done with it I thought I could just delete the guest OS to free up the needed storage space, but I had a usb external hard drive attached to the guest when I last used it, and I guess I didn't unmount the usb properly from the guest, because now that hard drive is no longer accessible to the host computer, even though it seems to recognize the hardware when I plug it in, I just can't see or access the drive. I tried plugging it into other computers to see if it would be accessible from them and it wasn't! So what do I do to get access to my usb hard drive again? Thanks in advance for your help.

What was the guest you were experimenting with? Did you by any chance format the drive for a foreign filesystem (one not supported by Windows)?

If you did that then the contents can only be accessed by the OS whose filesystem was placed on the drive. To make the drive usable in Windows again it would need to be reformatted in Windows.

The guest OS was Ubuntu 9.04, but the external hard drive wasn't reformatted, it's been formatted as fat32 for a long time. I even tried accessing it from a computer running Ubuntu but no dice.

Well, we've established that the drive is not usable on any PC, and there are precious few reasons for that to be the case. One is physical damage to the hardware, which I think we can discount, the other is that the filesystem on the drive has been "corrupted" somehow. Since I hope that Ubuntu does not make a habit of corrupting drives then I have to consider the most likely explanation is that you did something to it: repartitioned it, reformatted it, overwrote it with "dd", or something similar.

One problem with this explanation is that it should be quite hard for a guest to zap a host drive! That would mean that the guest was given access somehow: perhaps using "convertfromraw", perhaps it was directly mounted as a USB device visible to the guest. ... I must admit that letting two operating systems have potential low level access to the same drive at the same time is something I would automatically be suspicious about, hence it's a feature I've never attempted to use. I would have created a shared folder on the drive instead. However I have no evidence that it's possible to corrupt a drive in this way (and it's hard to see how: neither OS has a reason to make big changes to the partition map or root directory).

Do you actually need the contents of this drive? If not you could try reformatting under Windows, which would prove there has been no hardware failure. If you do need the contents then you could dd them off first (in fact the dd output might be easier to investigate to find out the nature of the corruption).

Sorry, I don't know what you mean by dd. I do need the data on the external drive, actually that's why I had it connected to the guest, I was trying to rename files that couldn't be accessed by Windows because they had characters in the filename that only Linux allows. I think the problem is that Virtual Box has some provisions for safely dismounting the usb drives, which I didn't realize before I had deleted the guest OS. I noticed that the external hard drive wasn't visible to the host even while the Guest was still running, i.e. it wasn't assigned a drive letter (e.g. F:). Now the external hard drive isn't even visible to any of my computers (i.e. it isn't mounted in linux or assigned a drive letter in Windows), so I wouldn't know how to go about even reformatting it.