[Tfug] Debian unable to mount root fs after an update/upgrade

[Stephen Hooper]

> Now on to my questions:
>
> 1) Why did running lilo fix the problem?

When the kernel loads it needs to know where to mount root from.
Without a root the kernel can't start init, and do all the other
interesting things it does.

The error you got is what you see when the kernel has been told to
mount the root disk from a certain location, and that location is
unreadable by the kernel.

Unlike Grub, LILO reads the kernel from "raw" sectors on the disk, not
from a file-system. Re-running LILO basically uploads the kernel you
want to boot into those raw sectors...

> 2) Do you have enough information to make a guess as to what went
>    wrong? Do you think there was anything I could have done
>    differently to prevent this problem?

>From the error the kernel was trying to use "/dev/hda1" as root.  That
jives with your fstab...

It either couldn't figure out how to open the device, or couldn't
figure out what kind of filesystem was inhabiting that device, both
are kind of weird errors, as one would mean that the kernel couldn't
find the device (usually if this happens you would be trying to read a
device that doesn't have drivers natively in the kernel (for example a
SCSI disk attached to a strange controller)), or that it couldn't read
an ext3 filesystem (which should be pretty mandatory in any standard
kernel).

VFS: Cannot open root device "301" or unknown-block(3,1)
Please append a correct "root=" boot option.
Kernel panic - not syncing: VFS: Unable to mount root fs on
  unknown-block(3,1)

I got all that from the above... 3,1 (ls -al /dev/hda ; ls -al
/dev/hda1) major, minor for hda1

Best guess is that running LILO either put a ramdisk in place with
something like a SATA driver (which I am not sure how necessary that
is anymore), or you were running some strange kernel with very little
support for anything...

As to the last part... stop doing strange things :) !

Hope that helps.