From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f50.google.com ([209.85.215.50]:56976 "EHLO mail-lf0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751344AbdKARwf (ORCPT ); Wed, 1 Nov 2017 13:52:35 -0400 Received: by mail-lf0-f50.google.com with SMTP id 90so3423089lfs.13 for ; Wed, 01 Nov 2017 10:52:35 -0700 (PDT) Subject: Re: Several questions regarding btrfs To: "Austin S. Hemmelgarn" , ST Cc: linux-btrfs@vger.kernel.org References: <1509467017.1662.37.camel@gmail.com> <1509480384.1662.84.camel@gmail.com> From: Andrei Borzenkov Message-ID: Date: Wed, 1 Nov 2017 20:52:24 +0300 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: 01.11.2017 15:01, Austin S. Hemmelgarn пишет: ... > The default subvolume is what gets mounted if you don't specify a > subvolume to mount.  On a newly created filesystem, it's subvolume ID 5, > which is the top-level of the filesystem itself.  Debian does not > specify a subvo9lume in /etc/fstab during the installation, so setting > the default subvolume will control what gets mounted.  If you were to > add a 'subvolume=' or 'subvolid=' mount option to /etc/fstab for that > filesystem, that would override the default subvolume. > > The reason I say to set the default subvolume instead of editing > /etc/fstab is a pretty simple one though.  If you edit /etc/fstab and > don't set the default subvolume, you will need to mess around with the > bootloader configuration (and possibly rebuild the initramfs) to make > the system bootable again, whereas by setting the default subvolume, the > system will just boot as-is without needing any other configuration > changes. That breaks as soon as you have nested subvolumes that are not explicitly mounted because they are lost in new snapshot.