RE: grub and root=label=

[Greg White]

> On Monday 08 September 2008 9:26:54 pm Greg wrote:
>>>As far as I know, the "root=" line is passed as one of the parameters to
>>>the booting kernel, so it shouldn't matter what version of Grub you're
>>>using. For instance, if you're running Linux, look at the Linux kernel
>>>documentation for the kernel in /Documentation/kernel-paraemeters.txt --
>>>you'll see that one of the parameters the kernel takes is the "root="
>>>parameter -- and that support is there regardless of you use an initrd
>>>image or not.
>>>
>>>The label that you need to enter in "root=LABEL=" is the label on the
>>>desired PARTITION, not the drive's VOLUME label. 'cfdisk' can list the
>>>partition labels along with the device names on the disk. For doing a
>>>double-check, have a look at the 'findfs' command.
>>
>> kernel-parameters.txt:
>> root= [KNL] Root filesystem
>>
>> I know I need the root= parameter. I need a way to point to a label
>> instead of hard coding a dev entry and no initrd.
>
> Are you compiling your own kernel? i.e. what are you doing to get rid of
> the initrd image requirement? I ask because all the popular distributions
> that I know of ship kernels that come with (and require) an initrd image by
> default.

Yes I am compiling my own kernel.  I am compiling everything I need into the 
kernel.  The policy (written by the previous admin) is to compile everything in 
as the kernel runs faster and is more secure.  There is no =m in the .config 
only =y or =n.

> I recently gave a presentation on the subject of compiling the Linux 2.6
> kernel a couple of months ago, and I went into the details of how to build
> the Linux kernel without an initrd image because that's how I like to build
> my own. The video and other talk materials are available.
>
> ftp://ftp.coredump.us/kernel-talk_05-13-2008/

I will look at it this afternoon.

>> I tried root=LABEL=WD320G in menu.lst and it didn't work.
>
> What error do you get? Was it a kernel panic due to not being able to find
> the root filesystem, i.e. "cannot find init"?

VFS: cannot open root device "LABEL=WD320G" on unknown-block(0,0)
please append a correct "root=" boot option
Kernel Panic-not syncing VFS: unable to mount root fs on unknown-block(0,0)
and the caps lock and scroll lock lights flash.

>> I used e2label to label the hard drive.
>
> Okay.
>
>> Here is the output from cfdisk:
>> cfdisk 2.12r
>>
>> Disk Drive: /dev/sdc
>> Size: 250059350016 bytes, 250.0 GB
>> Heads: 255 Sectors per Track: 63 Cylinders: 30401
>>
>> Name Flags Part Type FS Type [Label] Size
>> (MB)
>> ---------------------------------------------------------------------------
>>--- sdc1 Boot Primary Linux ext3 [WD320G] 249637.25
>> sdc2 Primary Linux swap 419.49
>>
>> findfs LABEL=WD320G
>> /dev/sdc1
>
> Good, thanks for including that info -- that looks like it checks out.
>
>> My /etc/fstab looks like this and works:
>> LABEL=WD320G / auto defaults 1 1
>
> Good.
>
>> What did I do wrong?
>
> As far as I can tell the problem is that the kernel you're trying to boot
> doesn't contain the necessary support to find the hard disk. Running 'lsmod'
> on a kernel that does boot properly (assuming said kernel uses an intrd image
> and thus loads drivers as modules) will give you some clues as to what device
> drivers you'll need to build-in to the kernel if you want to boot up without
> an initrd image. Running '/sbin/modinfo ' should give you an
> idea of whether a device driver module is disk related and thus required to
> build-in.

Everything is compiled in.  There are no modules.  Everytime I run a make 
menuconfig and make a change I do a grep for =m in the .config.
grep '=m' .config

Does it matter if I am compiling kernel 2.6.21.7?  I know it is an old kernel, 
but it is what I must work with.

>> Thanks,
>>
>> PS I know the drive is 250GB but labeled 320G.
>
> Is it? I didn't notice....
>
>> And sorry for the other post with the wrong subject.
>
> Thanks for reposting with the right subject.
>
> -- Chris
>
> --
>
> Chris Knadle
> address@hidden

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