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

[Stephen Hooper]

On 1/24/07, Glen Pfeiffer <glen at thepfeiffers.net> wrote:
> Hi Everyone,
>
> I recently started up a machine with Debian Etch that I had left
> unused for a few months. I performed an update/upgrade with
> aptitude (both upgrade and dist-upgrade), and now it won't boot.
>
> While the upgrade was executing, it asked me about replacing my
> kernel image (iirc) and said that if I am not 100% sure that I
> know what I am doing I should cancel, otherwise my system may not
> boot afterward. So I canceled that action, but it continued the
> rest of the upgrade without errors.
>
> I have not done anything to troubleshoot, because I have never
> encountered a failure to boot like this. Here is the last part of
> the boot messages:
>
> RamDisk: Couldn't find valid RAM disk image starting at 0.
> 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)
>
> Relative to you all, I am very new to Linux. I know how to
> install and use it, but can't diagnose problems. Heck, my first
> reaction was to "re-install", which shows my background in
> Windows. Of course I did not re-install yet because I hope to
> learn a little about troubleshooting Linux.
>
> So, can anyone help?
>

As Chris suggested:

- boot a Knoppix CD
- "dmesg" to make sure it found a drive... (could be you are using SCSI, etc).
   - you should see something identifying itself as a disk drive.
     - if you don't then you need to remake your RAMDISK to include
the right driver.
- assuming it boots: "su -"  to root if you aren't already, and at the
command prompt run "vgscan"
- if it returns something like:

  Reading all physical volumes.  This may take a while...
  Found volume group "vg00" using metadata type lvm2

  - then type in "vgchange -a y  /dev/vg00" (from "Found ... " above)
- now type in "fdisk -l /dev/disk" with the disk id you found from dmesg.
- you should see some partitions listed, check the types they have.
- you will need to find at least one "Linux".
- mkdir /mnt/root
- Now try "mount /dev/diskidpartid /mnt/root"
- chroot /mnt/root /bin/bash
- Now "mount -a"
- Now look in "/boot"
- See what changed.  Hopefully Debian tacked on to the grub
configuration instead of using it.

I would guess, this is probably one of three things: missing driver
for disk controller (but it seems to be reading /dev/hda), missing
driver for filesystem (you made your filesystems something weird), or
missing driver for something like the device mapper (logical volumes).