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

[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.

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

[Dale]

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

:-)  :-) 

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

[Stroller]

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.

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

[Dale]

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

:-)  :-)

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

[Stroller]

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.

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

[Dale]

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

:-)  :-) 

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

[Stroller]

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.

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

[Neil Bothwick]

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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?

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

[Stroller]

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.

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

[Neil Bothwick]

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

[Michael Hampicke]

>>
>> It would appear that you need an initrd/initramfs to use this.
>>
> 
> Ah! Many thanks. I will live without this shortcut, then, I think.
> 

If you, like me, prefere to compile your own kernel, there's still an
easy way to create a initrd for your kernel: with genkernel
I use this command to compile my pre-configured kernel

genkernel --no-clean --no-mrproper \
    --makeopts=-j2 --loglevel=5 --install --symlink all

To include support for disk labels use the switch --disklabel

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

[Stroller]

On 9 Feb 2009, at 10:32, Michael Hampicke wrote:

>>>
>>> It would appear that you need an initrd/initramfs to use this.
>>>
>>
>> Ah! Many thanks. I will live without this shortcut, then, I think.
>>
>
> If you, like me, prefere to compile your own kernel, there's still an
> easy way to create a initrd for your kernel: with genkernel
> I use this command to compile my pre-configured kernel
>
> genkernel --no-clean --no-mrproper \
>    --makeopts=-j2 --loglevel=5 --install --symlink all
>
> To include support for disk labels use the switch --disklabel



I am resistant to the idea of using an initrd, because IIRC it's an  
extra file that has to be stored in /boot, creating extra "clutter" in  
there.

I'm kinda thinking that using the label prevents failed boots in the  
event that the drives are recognised in a different order in the  
future, but nevertheless I don't "like" initrd and the longer kernel  
lines in grub.conf that they require.

I appreciate this is somewhat irrational.

Stroller.

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

[Alan McKinnon]

On Monday 09 February 2009 18:51:24 Stroller wrote:
> On 9 Feb 2009, at 10:32, Michael Hampicke wrote:
> >>> It would appear that you need an initrd/initramfs to use this.
> >>
> >> Ah! Many thanks. I will live without this shortcut, then, I think.
> >
> > If you, like me, prefere to compile your own kernel, there's still an
> > easy way to create a initrd for your kernel: with genkernel
> > I use this command to compile my pre-configured kernel
> >
> > genkernel --no-clean --no-mrproper \
> >    --makeopts=-j2 --loglevel=5 --install --symlink all
> >
> > To include support for disk labels use the switch --disklabel
>
> I am resistant to the idea of using an initrd, because IIRC it's an
> extra file that has to be stored in /boot, creating extra "clutter" in
> there.
>
> I'm kinda thinking that using the label prevents failed boots in the
> event that the drives are recognised in a different order in the
> future, but nevertheless I don't "like" initrd and the longer kernel
> lines in grub.conf that they require.
>
> I appreciate this is somewhat irrational.

Not really.

initrds are there for two cases, and only two cases: 1) a generic boot process 
for precompiled binary distros where the maintainers has no idea what the 
user has and must support all combinations for all possible users. 2) Boot 
scenarios where you require access to the root device before you have access 
to the root device (/ on lvm, boot off some raid setups, etc)

The first does not apply to gentoo at all. If you don't have the second, 
initrd is just extra unnecessary clutter and complexity and you are quite 
correct to resist it's presence.

-- 
alan dot mckinnon at gmail dot com

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

[Dirk Heinrichs]

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Am Montag, 9. Februar 2009 17:51:24 schrieb Stroller:

> I don't "like" initrd and the longer kernel  
> lines in grub.conf that they require.

Errh, which longer lines in grub.conf?

Here's mine, as an example:

title=Gentoo Linux
        kernel /vmlinux.gz realroot=/dev/evms/root vga=0x31B notsc

Quite short and simple, isn't it? You don't even recognize that it uses an 
initramfs (because it's embedded in the kernel itself).

Bye...

	Dirk

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

[Stroller]

On 9 Feb 2009, at 18:03, Dirk Heinrichs wrote:

> Am Montag, 9. Februar 2009 17:51:24 schrieb Stroller:
>
>> I don't "like" initrd and the longer kernel
>> lines in grub.conf that they require.
>
> Errh, which longer lines in grub.conf?
>
> Here's mine, as an example:
>
> title=Gentoo Linux
>        kernel /vmlinux.gz realroot=/dev/evms/root vga=0x31B notsc
>
> Quite short and simple, isn't it? You don't even recognize that it  
> uses an
> initramfs (because it's embedded in the kernel itself).

Am I not correct in thinking that initramfs used to be / can be / was  
originally a separate file which goes in /boot and is described with  
an extra boot parameter?

I wasn't aware that you could embed the initramfs into the kernel  
itself - after reading Neil's message yesterday I looked up more about  
the initramfs, contemplated about the idea of doing so and decided  
"naw, you'll never be able to do that, it would make the kernel too  
big and take up too much memory".

I certainly can recognise that you're doing something bogus, because  
your kernel parameters use "realroot=" and not just "root="

Stroller.

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

[Dirk Heinrichs]

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Am Montag, 9. Februar 2009 23:26:46 schrieb Stroller:

> Am I not correct in thinking that initramfs used to be / can be / was
> originally a separate file which goes in /boot and is described with
> an extra boot parameter?

Yes, you are. There are several ways nowadays. I use the easy one: Populate a 
directory tree with the contents of the initramfs and configure that directory 
in menuconfig. The kernel build system handles the details.

> I wasn't aware that you could embed the initramfs into the kernel
> itself - after reading Neil's message yesterday I looked up more about
> the initramfs, contemplated about the idea of doing so and decided
> "naw, you'll never be able to do that, it would make the kernel too
> big and take up too much memory".

Nope. It's freed right after swithing to the real root fs.

> I certainly can recognise that you're doing something bogus, because
> your kernel parameters use "realroot=" and not just "root="

Luckily the kernel ignores everything it doesn't know so you can give it any 
option you like. In this case I use "realroot" inside initramfs to tell it (by 
parsing /proc/cmdline) what's the real volume for the encrypted root device 
(/dev/mapper/c-root) listed in fstab.

Bye...

	Dirk

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

[Mick]

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On Monday 09 February 2009, Dirk Heinrichs wrote:
> Am Montag, 9. Februar 2009 17:51:24 schrieb Stroller:
> > I don't "like" initrd and the longer kernel  
> > lines in grub.conf that they require.
>
> Errh, which longer lines in grub.conf?
>
> Here's mine, as an example:
>
> title=Gentoo Linux
>         kernel /vmlinux.gz realroot=/dev/evms/root vga=0x31B notsc
>
> Quite short and simple, isn't it? You don't even recognize that it uses an
> initramfs (because it's embedded in the kernel itself).

How do you embed the initramfs in the kernel?
-- 
Regards,
Mick

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

[Albert Hopkins]

On Tue, 2009-02-10 at 18:46 +0000, Mick wrote:
> On Monday 09 February 2009, Dirk Heinrichs wrote:
> > Am Montag, 9. Februar 2009 17:51:24 schrieb Stroller:
> > > I don't "like" initrd and the longer kernel  
> > > lines in grub.conf that they require.
> >
> > Errh, which longer lines in grub.conf?
> >
> > Here's mine, as an example:
> >
> > title=Gentoo Linux
> >         kernel /vmlinux.gz realroot=/dev/evms/root vga=0x31B notsc
> >
> > Quite short and simple, isn't it? You don't even recognize that it uses an
> > initramfs (because it's embedded in the kernel itself).
> 
> How do you embed the initramfs in the kernel?

CONFIG_INITRAMFS_SOURCE