Re: Labels in grub2

[Barry Jackson <zen25000@zen.co.uk>]

On 04/11/10 12:12, Andrey Borzenkov wrote:
> On Wed, Nov 3, 2010 at 2:57 AM, Barry Jackson<zen25000@zen.co.uk>  wrote:
>>
>> In the meantime I have made some patches to demonstrate this idea in grub
>> 1.98 which I have attached.
>>
>
> gmail does not make it easy to quote patches :(
>
>> --- /usr/sbin/grub2-mkconfig	2010-11-02 22:38:20.610505816 +0000
>> +++ grub2-mkconfig	2010-11-02 22:35:32.000000000 +0000
>> +GRUB_DEVICE_LABEL=$(blkid ${GRUB_DEVICE}| grep "LABEL=" |tr -s 'LABEL=' '*' | cut -d* -f2 | cut -d'"' -f2)
>
> This is very elaborate way to implement
>
> GRUB_DEVICE_LABEL="$(blkid -s LABEL -o value ${GRUB_DEVICE})"
>
> :)
>
Neat thanks, I forgot that the latest blkid has that feature :-(
In the latest beta grub, grub-probe can be used instead of blkid for this.

> And you have to check whether blkid exists ...

Yes. I suppose it's possible that it may not be available. I was only 
thinking of Mandriva.

>
>> @@ -226,6 +233,8 @@
>>    GRUB_INIT_TUNE \
>>    GRUB_SAVEDEFAULT
>>
>> +
>> +
>>   if test "x${grub_cfg}" != "x"; then
>
> You probably should not introduce unrelated formatting changes.

I don't understand what you mean by that. Ah - those blank lines?
OK, yes, that was accidental. Must be more careful.

>
>> --- /etc/grub.d/10_linux	2010-11-02 22:25:19.849508548 +0000
>> +++ 10_linux	2010-11-02 22:05:31.000000000 +0000
>> @@ -42,11 +42,17 @@
>> +# If A label exists and GRUB_USE_LABEL=true is in /etc/default/grub  (bcj)
>> +   if [ "x${GRUB_DEVICE_LABEL}" != "x" ]&&  [ "x${GRUB_USE_LABEL}" = "xtrue" ]; then
>> +      LINUX_ROOT_DEVICE=LABEL=${GRUB_DEVICE_LABEL}
>
> Label may contain spaces as opposed to UUID, I think. Although I guess
> in real life label with spaces will cause much more problem elsewhere.
>   Same in grub-mkconfig_lib patch BTW
>
Yes labels can have spaces, but it's a bad idea and yes things do break, 
maybe LINUX_ROOT_DEVICE=LABEL="${GRUB_DEVICE_LABEL}" would be enough. Or 
maybe detect labels with spaces and exit 1 would be safer.
I will do more testing.

>> They work fine for me, with GRUB_USE_LABEL="true" set in /etc/default/grub
>> in my Mandriva-Linux systems.
>>
>> A grub.cfg produced with a patched grub2 is attached also.
>>
>> I am not a professional programmer, so I would appreciate any constructive
>> criticism, and your comments in general on this idea.
>
> I think it is fine as option as long as it is not default
I agree

> Labels have
> much more chances to duplicate than UUIDs.
>
If users can't think of unique labels then it's time to give up :-(

I really hope that the grub developers pick up this idea and run with it.

Thanks for your input.

Barry
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