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So I made a textbook error, and after I had got everything else working nicely on 12.04, thought I would try to upgrade my Nvidia drivers to "current", since that was recommended, in the hope it would improve 3D performance.

Slight problem: I can no longer boot my kernel. The error reads, in part:

Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
PID: 1, comm: swapper/0 Not tainted 3.2.0-31-generic #50-Ubuntu

That's followed by a call trace, which I'd rather not have to retype by hand unless it's necessary.

Recovery mode also does not work, giving the same error, but preceded by a whole dump of text. The two extra lines which precede the error above look interesting:

VFS: Cannot open root device "UUID=[long string of hex]" or unknown-block(0,0)
Please append a correct "root=" boot option; here are the available partitions:

followed by the same kernel panic message as above.

It's not a disk or filesystem error, as if I choose the previous kernel or a LiveCD it mounts fine.

Most of the suggestions I can find seem to revolve around purging the Nvidia drivers, but they tend to assume that users are able to boot the kernel, at least in text mode. Is there anything I can do via e.g. chroot or something?

Are the Nvidia drivers even involved, or is that just a coincidence? The root partition is on an Nvidia RAID device, but I don't know whether that is significant.

Thanks in advance for any help.

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This appears to be a bug. I would report it to Nvidia and then head over to the Nvidia Linux forums (yes, I know that it is not nvidia.com, but they link to them). As for getting your computer working again, I would recommend either reverting back to the older Nvidia drivers or using the open-source nouveau drivers. – InkBlend Oct 6 '12 at 1:31
Do you have any suggestion on how to revert if I can't boot that kernel? Sorry, I'm new to the Nvidia driver dance; my previous experiences with Ubuntu have been on a Thinkpad, which is gloriously uncomplicated. – riotnrrd Oct 6 '12 at 9:15
See this article about using chroot on a live CD to gain a command-line on a system (look after "chroot"). Note that while this makes Linux look insecure, a general rule of computer security is that anyone with unrestricted physical access can gain access to your OS, regardless of what it is (Linux, Windows or OS X). – InkBlend Oct 7 '12 at 0:51

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1 Answer

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If you're running AMD, Go into bios and disable IOMMU. (if you have it) Thats what happened to me.

You can add Kernel Option "IOMMU=PT" Double check that tho. It means pass-through.
I also added "IOMMU=1" Which i cant remember what or why... I think I thought that meant "enabled" but, dont quote that.

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Nope, sorry, Intel. I didn't make any BIOS changes either, just added the Nvidia current drivers to a kernel that was running fine and rebooted. Thanks for the suggestion though! – riotnrrd Oct 5 '12 at 19:19
Able to boot seperate kernel, but not main... Nvidia drivers... raid... Strange. Have you tried to boot with pure bios defaults? – TardisGuy Oct 5 '12 at 20:27
Well, pure BIOS defaults means the RAID stops acting as a RAID, which would probably cause its own problems. I hadn't changed anything in the BIOS recently though, so I doubt that's it. – riotnrrd Oct 6 '12 at 9:16

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