Bug#567468: (boot time consequences of) Linux mdadm superblock question.
> True. You'd have to update the superblock UUID right after creation
> of the filesystem. That doesn't sound like a robust strategy to
> making mdadm.conf optional.
it seems that, with "dracut", "mdadm.conf" is optional.
There is the kernel boot paramenter "rd_NO_MDADMCONF",
which forces "dracut" to do not use the "mdadm.conf" in
the initramfs image.
This seems to work also if / is on mdX.
I just tried it, and it was running fine. I did not check
the details, i.e. I've no proof "dracut" was not cheating.
My impression is that it uses the "mdadm -I" functionality.
There are other interesting kernel boot options, like: