From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.saout.de ([127.0.0.1]) by localhost (mail.saout.de [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id aAsPuzrQ89xW for ; Tue, 18 Dec 2012 09:57:45 +0100 (CET) Received: from v4.tansi.org (ns.km33513-03.keymachine.de [87.118.94.3]) by mail.saout.de (Postfix) with ESMTP for ; Tue, 18 Dec 2012 09:57:45 +0100 (CET) Received: from gatewagner.dyndns.org (84-74-164-49.dclient.hispeed.ch [84.74.164.49]) by v4.tansi.org (Postfix) with ESMTPA id 575871404001 for ; Tue, 18 Dec 2012 09:57:45 +0100 (CET) Date: Tue, 18 Dec 2012 09:57:44 +0100 From: Arno Wagner Message-ID: <20121218085744.GC19928@tansi.org> References: <20121218003612.GA14871@tansi.org> <50D02551.9050009@gmx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50D02551.9050009@gmx.de> Subject: Re: [dm-crypt] UUID question List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: dm-crypt@saout.de On Tue, Dec 18, 2012 at 09:12:01AM +0100, Marc Ballarin wrote: > Am 18.12.2012 01:36, schrieb Arno Wagner: > >On Mon, Dec 17, 2012 at 04:10:50PM -0800, David Li wrote: > >>Hi, I wonder if the dm-crypt partition UUID (shown in blkid -p ) can > >>be used to uniquely associate it with the set of keys the partition will > >>need. Are there any cases that the UUID would change during the partition's > >>lifetime? > > > >The UUID is actually a filesystem attribute, not a partition > >attribute... > > This depends on the partition format in use. For example GPT, and > maybe others, provide an additional UUID for partititons (actually > GPT even supports Labels): > > $ sudo blkid -p /dev/sda1 > /dev/sda1: LABEL="data_usb" > UUID="9b70c4bf-6b40-4be3-9cb7-030db682ad35" VERSION="1.0" > TYPE="ext4" USAGE="filesystem" PART_ENTRY_SCHEME="gpt" > PART_ENTRY_UUID="3d18a590-d329-4a82-be02-c3588098d625" > PART_ENTRY_TYPE="0fc63daf-8483-4772-8e79-3d69d8477de4" > PART_ENTRY_NUMBER="1" PART_ENTRY_OFFSET="2048" > PART_ENTRY_SIZE="3907027087" PART_ENTRY_DISK="8:0" > > Whereas dos/mbr does not: > > $sudo blkid -p /dev/sda1 > /dev/sda1: UUID="b786a3a4-26e7-4765-aed1-9bc472522c06" VERSION="1.0" > TYPE="ext4" USAGE="filesystem" PART_ENTRY_SCHEME="dos" > PART_ENTRY_TYPE="0x83" PART_ENTRY_FLAGS="0x80" PART_ENTRY_NUMBER="1" > PART_ENTRY_OFFSET="2048" PART_ENTRY_SIZE="63997952" > PART_ENTRY_DISK="8:0" > > While the GPT UUID should never change, it might happen if some > bogus resizing tool is used. > > So, if a LUKS-UUID is available I would always prefer it and only > fall back to partition UUIDs when not using LUKS. > > Regards, > Marc Interesting. Seems (again), my view of things is too simplistic ;-) Anyways, the gist is that change of UUIDs is not something that should ordionarily happen during the lifetime of whatever carries it. Arno -- Arno Wagner, Dr. sc. techn., Dipl. Inform., Email: arno@wagner.name GnuPG: ID: CB5D9718 FP: 12D6 C03B 1B30 33BB 13CF B774 E35C 5FA1 CB5D 9718 ---- One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision. -- Bertrand Russell