kernel panic: VFS: Unable to mount root fs

pat5star
pat5star used Ask the Experts™
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Hi all,

I'll start off by stating that I'm pretty new to linux so this could likely be a stupid newbie mistake. Here's the problem:

The kernel I have working is version 2.4.22 and I can still boot up to that. I compiled a 2.6 version and installed it in exactly the same way that the old version is, just appending 2-6 to the end of the file. I did this also with /etc/lilo.conf and ran lilo afterwards so when I reboot I get a menu that shows linux and linux-2.6

linux still boots up fine but when I try and boot up linux-2.6 I get some ouput and then a kernel panic with this message:

<snip>
VFS: Cannot open root device "888" or unknown-block(8,8)
Please append a correct "root=" boot option
Kernel panic: VFS: Unable to mount root fs on unknown-block(8,8)

I am running debian testing on a dell poweredge 1750. It has 2 Xeon processors and 1 scsi HD. The whole reason behind my compiling a kernel is trying to get support for high memory (this machine has 2 gigs of ram) and multi-processor support.

I doubt this has anything to do with lilo and suspect that I've somehow configured the kernel wrong. I am using reiserFS and I'm pretty sure I selected all scsi and driver support. Everything is compiled in and not as modules.

Any help would be greatly appreciated! Thanks in advance,

-Pat
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Commented:
Looks like more people have this problem with 2.6... Try adding this line to your lilo.conf to the new 2.6 section :
append = "root=/dev/sda8"

To get the correct value of the root device, boot into your 2.4 linux and do a 'df -k'. The device that shows up as "mounted on /" should be specified in your lilo.conf

Author

Commented:
Hi arjanh,

I added that to lilo and it still didn't work. I even tried at the startup prompt doing linux-2.6 root="/dev/sda8" which I think is effectively the same thing, and it too did not work.

-Pat

Author

Commented:
Looking at the error message I noticed it was slightly changed after adding the append line to lilo.conf. It now reads:

VFS: Cannot open root device "sda8" or unknown-block(0,0)
Please append a correct "root=" boot option
Kernel panic: VFS: Unable to mount root fs on unknown-block(0,0)

The root directory is sda8.
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Commented:
The problem may also be caused by devfs being enabled, try adding 'devfs=nomount' to the append line. If this is the case, you might get some more info at http://www.torque.net/sg/devfs_scsi.html
Commented:
could u check on IDE support, whether is turned on or not.
Check your .config and look for CONFIG_BLK_DEV_IDE and CONFIG_BLK_DEV_IDEDISK entries.

Commented:
also if u have root=LABEL=/ line in your lilo.conf, remove it/uncomment out.

Author

Commented:
Hi all,

Thanks for the help. It turns out it that I didn't have the right option selected for the scsi and I was sure I did. oops!

Anyways, I'll split the points amongst you for the effort. Thanks again,

-Pat

Commented:
Pat,

Please tell us what option you selected for scsi to fix this
try this..

$ df -h
<root directory>

edit your lilo.conf..

append = "root=<root directory>"

run lilo..

$ /sbin/lilo

$ reboot


Commented:
Hi,

I tried all the above things but still I am getting the same error.  Below I am giving my .config file .  I am doing this on Xeon mechine.  and Operating system is redhat 9.


Commented:
Hey,
Even I'm encountering the same problem. I checked my SCSI and IDE settings too, everything .. dunno whats gone wrong.

Basically can some1 tell me what root=LABEL=/ exactly means?
AS in, where is LABEL defined, why are there two = in this entry only, et al.?

Raseel.

Commented:
Hi, I had the same problem after recompiling my kernel.
Is reiserfs compiled in your kernel?
if its just a module then try making one initrd image with the reiserfs module
Hi you all.
it is the 2Gig boundary of the memory. there is a bug in kernel 2.6. So when you reduce your meemory to 1 G you'll see that you won't have any problem.

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