On Tue, April 7, 2009 10:16 pm, Doug Ledford wrote: > On Apr 7, 2009, at 2:05 AM, Goswin von Brederlow wrote: >> Doug Ledford <dledford@xxxxxxxxxx> writes: >> >>> Originally, mdadm used /var/run/mdadm/mdadm.map file to store the >>> temporary mappings of incrementally added devices to device names. >>> Unfortunately, this breaks incremental assembly if used early in the >>> booting process. Specifically, root may still be read only. Since >>> incremental assembly is largely a udev specific feature, and udev >>> needs a writable /dev tmpfs mount even when root is still read only, >>> it's safer to put our mdadm.map file in /dev/md so that we can write >>> to the map file no matter how early in the boot process we are >>> attempting to use incremental assembly. >> >> What about /lib/init/rw? > > Never heard of it. But, if / is read-only, why wouldn't that also be > read-only? because a tmpfs was mounted there. It's probably a Debian-specific thing. Why /var/run cannot be mounted from tmpfs nice and early too I don't know.. I understand that some people think /var/run needs to persist across reboots to preserve ownership of directories, but they are wrong :-) /var/run should be a tmpfs mount point very early. I have to say that putting the map file in /dev feels very icky to me. It isn't a device, and so doesn't belong in /dev. If we go around putting things somewhere convenient rather than where they belong, we quickly end up with a mess. So while it might be very pragmatic, I am currently dis-inclined to take the patch. Can you try asking your boot-script people to make /var/run be an early tmpfs ??? NeilBrown -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
