From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from queue01b.mail.zen.net.uk ([212.23.3.242]:39352 "EHLO queue01b.mail.zen.net.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755688AbaENNeO (ORCPT ); Wed, 14 May 2014 09:34:14 -0400 Received: from [212.23.1.1] (helo=smarthost01a.mail.zen.net.uk) by queue01b.mail.zen.net.uk with esmtp (Exim 4.72) (envelope-from ) id 1WkZK1-0002xZ-28 for linux-btrfs@vger.kernel.org; Wed, 14 May 2014 13:34:13 +0000 Received: from [82.70.68.182] (helo=www.chrestomanci.org) by smarthost01a.mail.zen.net.uk with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1WkZJz-000AI4-JZ for linux-btrfs@vger.kernel.org; Wed, 14 May 2014 14:34:11 +0100 Message-ID: <537370C8.8010606@chrestomanci.org> Date: Wed, 14 May 2014 14:34:00 +0100 From: David Pottage MIME-Version: 1.0 To: Wang Shilong , Eric Sandeen CC: linux-btrfs , jshubin@redhat.com Subject: Re: [PATCH] mkfs.btrfs: allow UUID specification at mkfs time References: <5372C457.3000706@redhat.com> <53731BE3.5010604@cn.fujitsu.com> In-Reply-To: <53731BE3.5010604@cn.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 14/05/14 08:31, Wang Shilong wrote: > On 05/14/2014 09:18 AM, Eric Sandeen wrote: >> Allow the specification of the filesystem UUID at mkfs time. >> >> (Implemented only for mkfs.btrfs, not btrfs-convert). > Just out of curiosity, this option is used for what kind of use case? > I notice Ext4 also has this option.:-) I have used it a few times when replacing the hard disc of a Linux system, while trying to leave everything else untouched. Many distros, including Debian and Ubuntu write the /etc/fstab to specify volumes by UUID instead of by label or device path. I have also had the misfortune to use an embedded system where the boot volume UUID was configured into the flash in a non obvious way, so the easiest fix was to set-up the boot and root volumes on the replacement hard disc to have the same UUID. Of course in either case I could have just taken a bit for bit copy of the source volume using dd, but that had it'd own problems because the destination was smaller. I also wanted to defrag the fs while copying it. -- David Pottage