[lfs-support] Kernel panic: VFS: unable to mount root fs

Bruce Dubbs bruce.dubbs at gmail.com
Sun May 15 12:37:00 PDT 2016

Paul Rogers wrote:
>> 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.
> Not to belabor the point, it's telling you that once the kernel
> completes startup it can't get to your root file system to start init.
> Presumably the kernel that booted is from LFS, not the Debian host.  The
> key configuration at this point is in /etc/fstab.  It, and the
> "root=/dev/sdaX" in your GRUB configuration, had better agree on where
> your new system is.

I agree with Paul, but as an interesting aside, I once accidentally booted 
a LFS partition with a debian kernel/initrd and it came up.  There were 
some issues because /lib/modules did not have the debian modules, but I 
did get to a command prompt.

In my experience, 'make defconfig' for the kernel is generally sufficient 
for an initial boot.  There may be some issues with some peripherals such 
as a network card driver missing, but it is probably enough to get a bash 

   -- Bruce

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