Re: [PATCH] md: allow changing set_name of running array

[NeilBrown <neilb@suse.com>]

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On Fri, Sep 01 2017, Michał Mirosław wrote:

> On Fri, Sep 01, 2017 at 10:07:29AM +1000, NeilBrown wrote:
>> On Wed, Aug 30 2017, Michał Mirosław wrote:
>> > Allow changing active array's set_name. This is the only way to
>> > safely update superblock on an array which carries a mounted fs.
>> 
>> Do you really need to change the set_name of an active array?
>> 
>> The name is only used when the array is actived, so wait until the next
>> time the array is stopped, and change the name then.
>> 
>> You can boot with a rescue CD or similar and use "--assemble
>> --update=name", or with a bit of effort you could get the normal boot
>> sequence to change the name.
>> 
>> I wouldn't object to adding something to mdadm so that it would read
>> something from mdadm.conf, and update the set name at boot time.
>> 
>> What is the underlying problem that you are trying to solve here?
>
> I had to fix /dev/md* naming on a system with no physical access.
>
> The problem was that despite matching mdadm.conf entries, arrays started
> with random 127-i indexes (because superblocks' set_names didn't match
> hostname, I guess).

That's odd.  If an array is listed in mdadm.conf, that is enough to tell
mdadm that it is "local" so that it doesn't need the hostname to match.
Can you show me exactly what was in your mdadm.conf?

Thanks,
NeilBrown

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