[lfs-support] Kernel panic: VFS: unable to mount root fs - Next Diagnostic Steps?

Nathan Bibb nathanbibb at gmail.com
Sun May 15 09:36:19 PDT 2016

I have finished all steps in LFS 7.9 on my old pentium -mmx machine, and
rather than overwrite the existing grub configuration, I ran "update-grub"
from the host Debian 7.5 system.

The LFS system was found and showed up in my Grub Menu, but when I boot to
that, I got the kernel panic mentioned in the subject line.

I searched first through the FAQ and mailing list archive, and I went
through the items listed in the FAQ:

- Did you specify the correct partition in /boot/grub/menu.lst?
    - I did not configure menu.lst since I was attempting to boot from the
host GRUB.  However, it looks like it is pointing at the right partition.
I have one HD, and LFS is on /dev/sda2. Root in the GRUB command line
indicates (hd0,msdos2), which appears correct to me.
- Is support for the hard drive enabled in the kernel. For SCSI this means
support for the specific SCSI adapter.
    - This hard drive is a standard IDE HD, and from what I can tell this
is enabled in the kernel configuration by default.
- Is support for the hard drive compiled into the kernel, not just as a
module. (Modules are stored on the filesystem. If a driver needed to access
the filesystem is stored as a module on that filesystem, well ... you know
... ;)
    - I did not enable anything in the kernel configuration as a module as
far as I know.
- Is support for the filesystem compiled into the kernel. Again, not a
module. Support for ext2 is enabled by default, but others like ext3,
reiser, jfs, and xfs are not.
    - I formatted the LFS partition as ext4, and enabled ext4 in the kernel
configuration (through 'make menuconfig').

I am not sure what my next diagnostic steps are.  I am sure there is
something I did wrong in the kernel configuration, but short of recompiling
the kernel and blindly changing the configuration settings, I am not sure
what my next steps are.

One item to note is that I did previously have an issue with Glibc, as
detailed in the thread " Glibc test error - Generating locale
de_DE.ISO-8859-1".  I don't _think_ this is the root of the issue I am
having now, but I have no way of knowing for sure (with my current limited

Any hints on next steps, or direction to documentation I may have missed,
would be appreciated.

Kind regards,
Nathan Bibb
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