Booting New LFS System Ends in Kernel Panic

Dan McGhee farmerdan at i-rule.net
Sun Apr 3 14:32:14 PDT 2005


Just completed an LFS 6.0 build--well Friday night.  Each time I try to 
boot I get:

Kernel panic:VFS:Unable to mount root fs on unkown-block (3,67)

I know that this subject is a FAQ.  I have made sure that ext2 and ext3 
are compiled into the kernel.  In addition, the drivers for the 
harddrives are compiled into the kernel.

I have Googled on this error and it seems that there are any one of over 
a million suggestions on how to fix this--most seem inappropriate for my 
situation.  At this point in time I don't know whether I have a GRUB or 
kernel situation.  I can boot both Mandrake 10.1 and Windows with no 
problem.

The only difference between Mandrake and LFS is that Mandrake uses an 
initrd.  Since I made the "title" entries different for each menu.lst 
that I have (LFS_6.0 in Mandrake and LFS 6.0 in LFS), I discoverd that 
I'm booting from the Mandrake partition.  I have made the LFS partition 
a primary and have used "makeactive" on boot.  All to no avail.  The 
entries for Mandrake and LFS are identical in each distro--except for 
the title.  Here they are:

> title Mandrake
> kernel (hd1,0)/boot/vmlinuz root=/dev/hdb1 acpi=ht resume=/dev/hdb6 
> splash=silent vga=788
> initrd (hd1,0)/boot/initrd.img
>
> title LFS_6.0
> root (hd1,2)
> kernel /boot/lfskernel-2.6.8.1 root=/dev/hdb3

Just to make sure everything was in place I ran:

setup (hd1,2)

in the grub shell.  It didn't complain about anything but not being able 
to "embed" the images and gave the message "that's not fatal."  It 
recognized all the appropriate filesystems--ext2.

The lines of kernel messages I get just before the panic are:

< NET: Registered protocol family 1
< NET: Registered protocol family 17
< NET: Registered protocol family 15
<VFS: Cannot open root device "hdb3" on unknown-block (3,67)
<Please append a correct "root= " boot option
<Kernel panic:VFS:Unvable to mount root fs on unkown-block (3,67)

In <dmesg> for booting Mandrake the same section gives:

<NET: Registered protocol family 1
<BIOS EDD facility v0.16 2004-Jun-25, 2 devices found
<init init/main.c:726
<md: Autodetecting RAID arrays.
<md: autorun ...
<md: ... autorun DONE.
<RAMDISK: Compressed image found at block 0
<VFS: Mounted root (ext2 filesystem).

I don't know if this is relevant.  It's different.  I can see the initrd 
mount.  But once again, I have seen no posts on this list with a similar 
situation, so it must be something I have done.

I also thought about room to mount the root filesystem.  I have 1G of 
RAM and my SWAP is 1G also.  The appropriate results of df are:

</dev/hdb3             3.8G  1.1G  2.6G  30% /mnt/lfs

and the results of <ls -alQ /mnt/lfs/boot are:

drwxr-xr-x   3 root root    4096 Apr     3 13:06 "."/
drwxr-xr-x  22 root root    4096 Apr    3 11:08 ".."/
-rw-r--r--       1 root root   26901 Apr   3 13:06 "config-2.6.8.1"
drwxr-xr-x    2 root root    4096 Apr     3 13:11 "grub"/
-rw-r--r--       1 root root 1685274 Apr  3 13:05 "lfskernel-2.6.8.1"
-rw-r--r--       1 root root  826198 Apr   3 13:06 "System.map-2.6.8.1"

so it looks like there's enough room to expand the kernel and mount the 
filesystem.

I must confess that I have reached the limits of my knowlege.  I have 
followed the book verbatim and didn't have any problems that I couldn't 
resolve.  Well, I just lied.  When I first began my build I mounted 
/mnt/lfs as an ext3 instead of an ext2 partition. But that shouldn't 
affect things, should it?

In running Mandrake I have noticed weird things with 2.6.8.1.  And I 
have not ever gotten it to run on my laptop.  Would compiling at 2.6.10 
or 2.6.11 be helpful?

If it's something I have compiled into the kernel, something that should 
be in the kernel or something that's not a module, I sure don't 
recognize it.

Please share your ideas with me regardless of how mundane they seem.  
I'm getting a little desperate.  I will surely appreciate any help and 
will try anything short of shooting the PC.  :)

Thanks,

Dan











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