Red Hat Bugzilla – Bug 80540
grub.conf option "root=LABEL=/" causes kernel panic
Last modified: 2007-04-18 12:49:20 EDT
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Description of problem:
since 7.3, i've been using a kernel line in grub.conf similar
kernel /vmlinux... ro root=LABEL=/ hdb=ide-scsi
having labelled /dev/hda1, my root partition, with the
however, since i upgraded to the red hat updates version
of kernel 2.4.20-2.2, specifying my root filesystem using
"LABEL=/" causes the following at boot time:
VFS: Cannot open root device "LABEL=/" or 00:00
Please append a correct "root=" option
kernel panic: VFS: Unable to mount root fs on 00:00
i can get around this by editing the grub kernel line
and substituting "root=/dev/hda1" and it will boot fine.
but this shouldn't be necessary -- the LABEL option has
worked for quite some time until 2.4.20-2.2.
i have verified that all of the partitions are still
properly labelled, and unique. in addition, one other
participant on the redhat mailing list reported exactly
the same error.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. use a "LABEL=/" option in /etc/grub.conf
Actual Results: should boot properly
Expected Results: kernel panic, see above
does your grub.conf list an initrd ?
never mind, someone else on the redhat list suggested that it was
the lack of an initrd file that was the problem. apparently, even
though i had all the modules i needed built into the kernel, the
initrd file was still necessary to be able to use a LABEL option
in grub.conf. without one, it's necessary to use the explicit device name.
at least, that's the way it looks, and things work fine now.
I can boot a custom redhat kernel without initrd if ext3 is compiled into the
kernel. grub.conf has root=LABEL=/.
The problem occurs with non redhat kernels (eg. fresh download from kernel.org).
Perhaps redhat kernels have a certain configuration default which allows labels
to be read?
the kernel doesn't use this. At all.
you HAVE to have an initrd to use LABEL for root.
I had ext3 compiled into the kernel but still the problem persisted.
But removing the root=LABEL=/ itself from grub.conf let my box boot
fully without any issues.