Comment 37 for bug 136252

Adopting from #226484 (now a duplicate of this one):

This is a bug with mdadm --incremental not doing hotplug, because it looks for permission to do so in mdadm.conf.

On hotplug systems mdadm.conf should not have to contain any specific references, to make things clear and for backwards compatibility maybe it could contain explicit "any" statements like this:?

DEVICE <any>
HOMEHOST <any>
ARRAY <any>

This whole bussiness of locking down array assembly (homehost,ARRAY) may just be due to the historical (suboptimal) mdadm design to assamble raids going by major/minor numbers saved in the superblocks. Those should always be considered being dynamic (depreciated as a reference). Using --assemble --uuid mdadm takes a UUID and matches this unique but same UUID to determine member devices, this is appropriate for default behavour.

Of course we should refrain from running arrays that are not complete (to avoid leading them to desync by subsequent writes), unless it is required to recover data or boot from a specific failed array. For this case we should use --run <specific device> manually or in a startup scripts.