[gentoo-user] Using "root=LABEL=xxxx" in grub.conf

[Stroller]

Hi there,

Is anyone using "root=LABEL=xxxx" grub.conf, please? Anyone also using  
ext4 for their root?

I can find numerous references to this syntax going back to 2005 or  
so, and some major distros seem to use it as the default way of  
describing "root=" to the kernel.

http://www.linuxforums.org/forum/redhat-fedora-linux-help/23010-root-label-grub-conf.html
http://linux.derkeiler.com/Mailing-Lists/RedHat/2005-01/0026.html

But it doesn't work for me. :(

Here's a working configuration:

	stroller@hex ~ $ cat /etc/fstab
	# /etc/fstab: static file system information.
	#
	# <fs>			<mountpoint>	<type>		<opts>		<dump/pass>
	
	# NOTE: If your BOOT partition is ReiserFS, add the notail option to  
opts.
	LABEL=boot		/boot		ext2		noauto,noatime	1 2
	LABEL=root		/		ext4		noatime		0 1
	LABEL=swap		none		swap		sw		0 0
	/dev/cdrom		/mnt/cdrom	auto		noauto,ro	0 0
	
	# glibc 2.2 and above expects tmpfs to be mounted at /dev/shm for
	# POSIX shared memory (shm_open, shm_unlink).
	# (tmpfs is a dynamically expandable/shrinkable ramdisk, and will
	#  use almost no memory if not populated with files)
	shm			/dev/shm	tmpfs		nodev,nosuid,noexec	0 0
	
	stroller@hex ~ $ sudo mount -v -L boot
	/dev/sda1 on /boot type ext2 (rw,noatime)
	stroller@hex ~ $ cat /boot/grub/grub.conf
	default 0
	timeout 30
	splashimage=(hd0,0)/boot/grub/splash.xpm.gz
	
	title Gentoo Linux 2.6.28-gentoo-r1
	root (hd0,0)
	kernel /boot/bzImage-2.6.28-gentoo-r1 root=/dev/sda6
	
	stroller@hex ~ $


If I simply change the kernel line of grub.conf to:

	kernel /boot/bzImage-2.6.28-gentoo-r1 root=LABEL=root

Then I get a kernel panic upon boot:
    VFS: Cannot open root device "LABEL=root" or unknown-block(0,0)
    Please append a correct "root=" boot option; here are the  
available partitions:
    ...
    Kernel Panic - not syncing: VFS Unable to mount root fs on unknown- 
block(0,0)

Full screenshot of kernel panic:
    http://stuff.stroller.uk.eu.org/KernelPanic.png


Googling this error brings up quite a number of hits, and I reckon I  
must have spent a couple of hours now trying the most popular  
resolutions. This is quite a minor error - if I wasn't such an  
obsessive-compulsive I could easily ignore it, but I am, and it's  
frustrating the heck out of me.

One forum thread / bug report suggests the ata_piix module is to  
blame, but compiling that statically into my kernel doesn't help.
http://www.linuxquestions.org/questions/fedora-35/fc2-vfs-cannot-open-root-device-label-or-unknown-block00-269230/
https://bugzilla.redhat.com/show_bug.cgi?id=126953

Another post (can't find the reference now) suggests disabling  
"Initial RAM filesystem and RAM disk (initramfs/initrd) support" but  
that doesn't make any difference, either.

Finally, this thread <http://kerneltrap.org/node/2318> says "check  
your .config and look for CONFIG_BLK_DEV_IDE and  
CONFIG_BLK_DEV_IDEDISK entries." This is quite an old post, however,  
and these options aren't available in 2.6.28 (from my distro); I  
enabled CONFIG_BLK_DEV_IDEPCI instead, but it has no positive effect.

I had better mention that I am using a 3ware 9500 RAID controller on  
the PCI bus. I suspect the problem is specific to this (and my  
combination of modules / compiled-in kernel drivers), but I thought I  
would throw the question out there & see if any other ext4 users had  
also seen the same thing.

Thanks in advance for any suggestions,

Stroller.