[systemd-devel] install Fedora systemd-nspawn container on btrfs

[arnaud gaboury]

On Thu, Apr 23, 2015 at 2:00 PM, Lennart Poettering
<lennart at poettering.net> wrote:
> On Thu, 23.04.15 14:57, Andrei Borzenkov (arvidjaar at gmail.com) wrote:
>
>> On Thu, Apr 23, 2015 at 2:50 PM, Lennart Poettering
>> <lennart at poettering.net> wrote:
>> > On Thu, 23.04.15 13:45, arnaud gaboury (arnaud.gaboury at gmail.com) wrote:
>> >
>> >> Not sure what I did wrong, but I can't install/boot my nspawn container.
>> >> Here is my setup:
>> >>
>> >> Archlinux box- updated
>> >>
>> >> 1- created 3 btrfs subvol on /dev/sdb1 (SSD). The goal is to manage
>> >> snapshots easily.
>> >> no nested subvol.
>> >> ------------------------------------------
>> >> # btrfs subvolume list .
>> >> ID 266 gen 39 top level 5 path rootvol
>> >> ID 268 gen 41 top level 5 path var
>> >> ID 269 gen 42 top level 5 path etc
>> >> # btrfs filesystem show
>> >> Label: 'poppy-root'  uuid: ef1b44cd-e7b0-4166-b933-e7d4d20a1171
>> >>     Total devices 1 FS bytes used 64.00KiB
>> >>     devid    1 size 80.00GiB used 12.00MiB path /dev/sdb1
>> >> --------------------------------------------------
>> >>
>> >> 2 - mount btrfs subvol
>> >> -------------------------------------------------------------------
>> >> # mount -t btrfs -o subvol=rootvol /dev/sdb1 /var/lib/machines/enl
>> >> # mkdir /var/lib/machines/enl/var
>> >> # mkdir /var/lib/machines/enl/etc
>> >> # mount -t btrfs -o subvol=etc /dev/sdb1 /var/lib/machines/enl/etc
>> >> # mount -t btrfs -o subvol=var /dev/sdb1 /var/lib/machines/enl/var
>> >> --------------------------------------------------------------------
>> >
>> > THis isn't really how one would normally use subvolumes. No need to
>> > mount each subvolume explicitly, they are just special directories...
>>
>> As long as you never clone parent volume (but why use btrfs then?) As
>> soon as you create clone or snapshot of parent volume, all childs will
>> be out of place in it unless you explicitly mount them in correct
>> place in hierarchy.
>
> Hmm? not following. The "btrfs" tool surely doesn't do recursive
> snapshots currently. But it doesn't reinstate mount points either (or
> even makes them persistent), hence I really don't get what you are
> saying.
>
> (note that machined's clone command in git *does* recursive snapshots)

I am not a Btrfs expert, but from what I understood, and after some
posts on Btrfs ML[0], creating and mounting these subvol was the right
way to easily manage snapshots.

[0]http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg42856.html
>
> Lennart
>
> --
> Lennart Poettering, Red Hat



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