Re: dracut: qestions about mdraid module

[Francis Moreau <francis.moro-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 10/20/2014 01:02 PM, Harald Hoyer wrote:
> On 27.09.2014 17:21, Francis Moreau wrote:
>> Hello,
>>
>> I'm looking at the module 'mdraid' of dracut (0.38) and was wondering
>> the purpose of rd.md.uuid= parameter.
>>
>> I understand it can be used to selectively activate the array matching
>> the UUID passed through the parameter but I'm wondering in which cases
>> it can be useful...
>>
>> Also I don't really understand why dracut try to do its own mechanism to
>> achieve that (by providing its own udev rules which are modified at boot
>> time) whereas mdadm already provide the infrastructure (through
>> mdadm.conf) in a cleaner way (IMHO).
> 
> 
> If mdadm.conf is not included in the initramfs, you want to have a way to
> prevent automatic assembly of all raids found. With big machines, lots of disk,
> you only want to assemble those, which you really need.
> 

Ok but why mdadm.conf wouldn't be included in the initramfs ? If one
doesn't want to start all arrays during the boot process, it's very
likely he doesn't start all arrays automatically while the system is
running, no ?

>>
>> Another question, hopefully you don't mind: dracut provide an udev set
>> of rules in a file named 59-persistent-storage-md.rules. I still don't
>> really see the point since most of the stuff in it seems to already be
>> done by the rule fileudev-md-raid-arrays.rules, shipped by mdadm (3.3.2).
> 
> That wasn't always the case in all distributions. Nowadays can probably be removed.
> 
>>
>> Ah my last question not related to mdraid: why dracut uses stderr to
>> print out all its messages: info, debug, error. Stderr is usually used
>> for error/warning messages only.
>>
>> Thanks !
> 
> Hmm, not true.
> 
>     warn() {
>         echo "Warning: $*" >&2
>     }
> 
>     info() {
>         echo "$*"
>     }
> 
> 
> see.. warn() goes to error, info() to stdout.
> 
> This is in the initramfs, though.
> Or do you mean dracut the tool?
> 

Yes I meant dracut tool used to generate initramfs.

Thanks.