From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joel Becker Date: Sat, 16 Jun 2007 07:31:32 +0000 Subject: Re: udev and md/dm Message-Id: <20070616073132.GA3762@tasint.org> List-Id: References: <20070616002057.GI20024@tasint.org> In-Reply-To: <20070616002057.GI20024@tasint.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-hotplug@vger.kernel.org On Sat, Jun 16, 2007 at 04:32:49AM +0200, Kay Sievers wrote: > On 6/16/07, Joel Becker wrote: > > Why does udev ignore md* and dm-* devices for persistent naming? > >I was utterly surprised to find that an ext3 on /dev/md0 or /dev/dm-0 > >won't show up in /dev/disk/by-uuid. Given that dm and md devices can > >change names, isn't this something we'd really like to have? > > Sure, they just have their own rules files. Both have specific > requirements/lifetime-rules and plug into "change" events. I'm looking at rhel5, debian, and raw udev-105, and I can't find anywhere in the rules that use vol_id to map md or dm devices to /dev/disk/by-label and /dev/disk/by-uuid. The vol_id using files (persistent.rules) skips those devices. I can see why perhaps you'd say "loop and ramdisk may be garbage", but dm*, md*, and similar are expected persistent environment things. And their names can certainly change. I ask because I am looking at implementing a robust "how to determine what device is meant by UUID xxxxx". Robust in the face of catching the raid1 and multipath and so on. So /dev/disk/by-uuid/xxxxx wouldn't point to /dev/sdd1 if it really should be /dev/md0. I had hoped udev + vol_id would do this for me, as vol_id seems to have explicit ordering to make this work right. But the udev rules skip checking uuids and labels on the aggregate devices. Please, show me where I'm wrong :-) Joel -- "The question of whether computers can think is just like the question of whether submarines can swim." - Edsger W. Dijkstra Joel Becker Principal Software Developer Oracle E-mail: joel.becker@oracle.com Phone: (650) 506-8127 ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Linux-hotplug-devel mailing list http://linux-hotplug.sourceforge.net Linux-hotplug-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel