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Old 02-09-2009, 06:26 AM
Stroller
 
Default Using "root=LABEL=xxxx" in grub.conf

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.
 
Old 02-09-2009, 06:42 AM
Dale
 
Default Using "root=LABEL=xxxx" in grub.conf

Stroller wrote:
> 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.
>
>
>

You may have done this but just in case, you did use the tools to set
the label on the drive right? tune2fs does it for ext2 and ext3. I'm
not sure about ext4.

I only mention this cause this sounds like something I would do.

Dale

:-) :-)
 
Old 02-09-2009, 06:56 AM
Stroller
 
Default Using "root=LABEL=xxxx" in grub.conf

On 9 Feb 2009, at 07:42, Dale wrote:

Stroller wrote:

...
stroller@hex ~ $ sudo mount -v -L boot
/dev/sda1 on /boot type ext2 (rw,noatime)
stroller@hex ~ $

...
You may have done this but just in case, you did use the tools to set
the label on the drive right? tune2fs does it for ext2 and ext3. I'm
not sure about ext4.


Good question! I thought for a moment that the above demonstrated that
I had done so, but of course it is necessary to boot from a LiveCD
instead:


root@sysresccd /root % mount -v -L root /mnt/gentoo
mount: you didn't specify a filesystem type for /dev/sda6
I will try type ext4
/dev/sda6 on /mnt/gentoo type ext4 (rw)
root@sysresccd /root %

Stroller.
 
Old 02-09-2009, 07:02 AM
Dale
 
Default Using "root=LABEL=xxxx" in grub.conf

Stroller wrote:
>
> On 9 Feb 2009, at 07:42, Dale wrote:
>> Stroller wrote:
>>> ...
>>> stroller@hex ~ $ sudo mount -v -L boot
>>> /dev/sda1 on /boot type ext2 (rw,noatime)
>>> stroller@hex ~ $
>> ...
>> You may have done this but just in case, you did use the tools to set
>> the label on the drive right? tune2fs does it for ext2 and ext3. I'm
>> not sure about ext4.
>
> Good question! I thought for a moment that the above demonstrated that
> I had done so, but of course it is necessary to boot from a LiveCD
> instead:
>
> root@sysresccd /root % mount -v -L root /mnt/gentoo
> mount: you didn't specify a filesystem type for /dev/sda6
> I will try type ext4
> /dev/sda6 on /mnt/gentoo type ext4 (rw)
> root@sysresccd /root %
>
> Stroller.
>
>
>

Since ext4 is new and I have no experience with it yet, you may want to
take this lightly. I think cfdisk, or fdisk, would show if the label
was set or not. It to my knowledge can't change the label but it does
show it if it is set. It should do that even if booted from the drive
as well, just don't change anything. ;-)

Dale

:-) :-)
 
Old 02-09-2009, 07:03 AM
Stroller
 
Default Using "root=LABEL=xxxx" in grub.conf

On 9 Feb 2009, at 07:56, Stroller wrote:

...
You may have done this but just in case, you did use the tools to set
the label on the drive right? tune2fs does it for ext2 and ext3.
I'm

not sure about ext4.


Good question! I thought for a moment that the above demonstrated
that I had done so, but of course it is necessary to boot from a
LiveCD instead:


root@sysresccd /root % mount -v -L root /mnt/gentoo
mount: you didn't specify a filesystem type for /dev/sda6
I will try type ext4
/dev/sda6 on /mnt/gentoo type ext4 (rw)
root@sysresccd /root %


I should have said:

Thank you for the suggestion, though.

Stroller.
 
Old 02-09-2009, 07:10 AM
Dale
 
Default Using "root=LABEL=xxxx" in grub.conf

Stroller wrote:
>
> On 9 Feb 2009, at 07:56, Stroller wrote:
>>> ...
>>> You may have done this but just in case, you did use the tools to set
>>> the label on the drive right? tune2fs does it for ext2 and ext3. I'm
>>> not sure about ext4.
>>
>> Good question! I thought for a moment that the above demonstrated
>> that I had done so, but of course it is necessary to boot from a
>> LiveCD instead:
>>
>> root@sysresccd /root % mount -v -L root /mnt/gentoo
>> mount: you didn't specify a filesystem type for /dev/sda6
>> I will try type ext4
>> /dev/sda6 on /mnt/gentoo type ext4 (rw)
>> root@sysresccd /root %
>
> I should have said:
>
> Thank you for the suggestion, though.
>
> Stroller.
>
>
>

Your welcome. Here is some more info.

cfdisk (util-linux-ng 2.14.1)

Disk Drive: /dev/hdb
Size: 80026361856 bytes,
80.0 GB
Heads: 255 Sectors per Track: 63
Cylinders: 9729

Name Flags Part Type FS
Type [Label] Size (MB)
--------------------------------------------------------------------------------------------------------------------------
hdb1 Primary Linux
ext3 [backup] 80023.75


That partition is labeled "backup" on there. It is a drive I am not
using so I could umount it to set the label.

Hope that helps.

Dale

:-) :-)
 
Old 02-09-2009, 08:04 AM
Stroller
 
Default Using "root=LABEL=xxxx" in grub.conf

On 9 Feb 2009, at 08:02, Dale wrote:

...
root@sysresccd /root % mount -v -L root /mnt/gentoo
mount: you didn't specify a filesystem type for /dev/sda6
I will try type ext4
/dev/sda6 on /mnt/gentoo type ext4 (rw)
root@sysresccd /root %
....


Since ext4 is new and I have no experience with it yet, you may want
to

take this lightly. I think cfdisk, or fdisk, would show if the label
was set or not. It to my knowledge can't change the label but it does
show it if it is set. It should do that even if booted from the drive
as well, just don't change anything. ;-)


Hi Dale,

Thanks for your help. I thought the above DID demonstrate that the
partition is labelled correctly - does the -L flag not say "mount the
partition with the following label"?


Anyway, I checked with cfdisk, and because the output is formatted a
bit too pretty for email I found another way to check the
partition's / filesystem's label:


$ sudo e2label /dev/sda1
boot
$ sudo e2label /dev/sda6
root
$

This matches the label I was using in grub.conf:

$ grep LABEL= /boot/grub/grub.conf
#kernel /boot/bzImage-2.6.28-gentoo-r1 root=LABEL=root
$

Stroller.
 
Old 02-09-2009, 08:18 AM
Neil Bothwick
 
Default Using "root=LABEL=xxxx" in grub.conf

On Mon, 9 Feb 2009 07:26:38 +0000, Stroller wrote:

> 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.

It would appear that you need an initrd/initramfs to use this.

http://mulix.livejournal.com/84768.html


--
Neil Bothwick

Can you be a closet claustrophobic?
 
Old 02-09-2009, 08:28 AM
Stroller
 
Default Using "root=LABEL=xxxx" in grub.conf

On 9 Feb 2009, at 09:18, Neil Bothwick wrote:


On Mon, 9 Feb 2009 07:26:38 +0000, Stroller wrote:


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.


It would appear that you need an initrd/initramfs to use this.

http://mulix.livejournal.com/84768.html


Ah! Many thanks. I will live without this shortcut, then, I think.

I bow to your vastly superior Google-Fu.

Stroller.
 
Old 02-09-2009, 08:41 AM
Neil Bothwick
 
Default Using "root=LABEL=xxxx" in grub.conf

On Mon, 9 Feb 2009 09:28:42 +0000, Stroller wrote:

> I bow to your vastly superior Google-Fu.

Not really, I just hit the same problem as you a while ago, and came up
with the same solution.


--
Neil Bothwick

Adolescence, n.: The stage between puberty and adultery.
 

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