From mboxrd@z Thu Jan 1 00:00:00 1970 From: Doug Ledford Subject: Re: [Patch] mdadm: move mdadm.map file into /dev/md Date: Tue, 7 Apr 2009 08:16:37 -0400 Message-ID: References: <87tz51dmmu.fsf@frosties.localdomain> Mime-Version: 1.0 (Apple Message framework v930.3) Content-Type: multipart/signed; protocol="application/pgp-signature"; micalg=pgp-sha1; boundary="Apple-Mail-45-953875774" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87tz51dmmu.fsf@frosties.localdomain> Sender: linux-raid-owner@vger.kernel.org To: Goswin von Brederlow Cc: LinuxRaid RAID , Neil Brown List-Id: linux-raid.ids This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --Apple-Mail-45-953875774 Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit On Apr 7, 2009, at 2:05 AM, Goswin von Brederlow wrote: > Doug Ledford 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? > You say largely udev specific so there might not be an udev running > and no tmpfs on /dev. Generally speaking, it's only ever going to be used by udev or run manually. I doubt people will use it in things like rc.sysinit. However, regardless of all that, udev is started before any manual device bringups, so even if someone did decide to use it manually in rc.sysinit when root is still read only, udev will already be up by then. The only exception to this would be a system that doesn't use udev at all, in which case they get what they get, and /dev/md/ mdadm.map is no better or worse than /lib/init/rw than /var/run/mdadm. -- Doug Ledford GPG KeyID: CFBFF194 http://people.redhat.com/dledford InfiniBand Specific RPMS http://people.redhat.com/dledford/Infiniband --Apple-Mail-45-953875774 content-type: application/pgp-signature; x-mac-type=70674453; name=PGP.sig content-description: This is a digitally signed message part content-disposition: inline; filename=PGP.sig content-transfer-encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.11 (Darwin) iEYEARECAAYFAknbRCoACgkQQ9aEs6Ims9jdpACgyBYD/TskuvJ89/ZidzXQi8rw RUEAmQE5m9lVG5+axTW7+GnRBJVOgz+V =IXsk -----END PGP SIGNATURE----- --Apple-Mail-45-953875774--