[sles-beta] Fwd: [opensuse-factory] Re: grub2: booting from btrfs snapshots

[Darren Thompson]

Team

I was wondering how this was supposed to work for a "full rollback"

I saw this summary and thought it was useful to forward here...

Darren
---------- Forwarded message ----------
From: Matthias G. Eckermann <mge at suse.com>
Date: Mon, Aug 11, 2014 at 6:06 PM
Subject: Re: [opensuse-factory] Re: grub2: booting from btrfs snapshots
To: "Matwey V. Kornilov" <matwey.kornilov at gmail.com>,
opensuse-factory at opensuse.org


Hello Matwey and all,

On 2014-08-09 T 22:47 +0400 Matwey V. Kornilov wrote:
> 09.08.2014 22:34, Matwey V. Kornilov пишет:
> > 09.08.2014 21:51, Andrey Borzenkov пишет:
> >>
> >> There were quite a number of commits to support
> >> booting from btrfs snapshots. So I assume this
> >> should work, at least under some restrictions.
> >
> > Just installed 13.2, there are grub2-snapper-plugin
> > package, but it doesn't work out of the box. Trying
> > to understand what is to do with it.
>
> Ok. Get it working. When I boot into the snapshot,
> the / seems to be mounted as ro, and the OS is almost
> not working. Is it supposed to be so?

Yes. -- Booting from a snapshot can be used in two ways:

1. You chose a RO Snapshot in the Grub2 menu. In this
   case you will boot into a RO Snapshot, and you
   should  be able to work in this system. If you want
   to stay in this "state", you will have to copy the
   RO Snapshot into a RW, reboot and work from it.

   Sounds complex!? Maybe, but there is a reason for this:
   The assumption is that the majority of people will
   use RO Snapshots as "well known states" into which
   they want to jump back in case of emergency.
   If we would boot into such a snapshot "RW", the
   state would be changed, would not be "well known"
   anymore. In other words, it would be a "one time
   use well known state". Not very helpful, ...
   For that reason, booting into "RO" and changing to
   RW afterwards is a right way, as it preserves the
   "well known state" in the RO snapshot.

   The perfect solution would be, if Grub2 would be
   able to clone the (existing) RO into a (new) RW
   btrfs snapshot. But I don't know if it is even
   possible to implement this into Grub2.

2. If you are in a running system, you can chose:
        "snapper rollback <number>",
   reboot,
   and you are in a RW copy of <number>.

Hope this explains (a bit).

so long -
        MgE


--
Matthias G. Eckermann     Senior Product Manager   SUSE® Linux Enterprise
SUSE LINUX Products GmbH  Maxfeldstraße 5          90409 Nürnberg Germany
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-- 

Darren Thompson

Professional Services Engineer / Consultant

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Mail: darrent at akurit.com.au <steve at akurit.com.au>
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