[sles-beta] Thinking about SLES11 migration testing, BTRFS and sub-volumes?

Tue Aug 19 18:01:44 MDT 2014

Matthias

Thank you for a truly comprehensive answer.

I'm still unclear on one point though...

I believe an "in place" update from SLES11 => SLES12 is tested and a viable
option (please correct me if I'm incorrect).

That leaves the default ext3 file-system from SLES11 so you miss out on the
SLES12 roll-back advantage (as you have clearly explained).

I was under the impression that there was a straight forward process to go
from ext3 => BTRFS but I now see that there are a lot of "prerequisites"
that may be more difficult to meet.

Assuming that the SLES11 => SLES12 is done in one step and the ext3
file-system is migrated as a separate process, is there actually a guide as
to what steps are required to achieve that e.g.
{this is a guess at the process}
1. Boot from SLES12 media and go into "recovery mode"
2. Using appropriate tool make backup copy of '/', '/boot' and any other
required file-systems.
3. Create appropriate BTRFS root filesystem using command line 'xxxx" which
creates required '/' and "default' sub-volumes (including snapshots).
4. mount BTRFS '/' and sub-volumes in temporary location, restore backed up
'/', '/boot' and other file-systems to new BTRFS file-system.
5. Chroot into BRTFS '/' and restore bootloader config etc **** or remount
root filesystem *** Not sure of this part....
6. Reboot
7. setup snapper config etc

Is this close to correct and is it worth testing as a Beta tester???

Regards
Darren

5.

Darren Thompson

Professional Services Engineer / Consultant

 *[image: cid:image001.jpg at 01CB7C0C.6C6A2AE0]*

Level 3, 60 City Road

Southgate, VIC 3006

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

On 20 August 2014 08:48, Matthias G. Eckermann <mge at suse.com> wrote:

> Hello Darren and all,
>
> On 2014-08-20 T 07:51 +1000 Darren Thompson wrote:
>
> > Just thinking out loud, please ignore if not relevant
> > to you...
>
> the question indeed is important, thus let me answer in
> two steps:
> I. What we do (not) support and why (not)
> II. How you may achieve (soon) what you are looking for
>
>
> Ad I. What we do (not) support and why (not)
>
> Let me share some SUSE internal discussion (from 2012
> already): Back then we discussed, if we should support
> the in place migration of SLES 11 to SLES 12 including a
> migration of ext3 to btrfs.
>
> And we decided against this for one simple reason: complexity.
>
> If you look at the changes from SLES 11 to SLES 12:
> - default filesystem    ext3     -> btrfs
> - bootloader            grub1    -> grub2
> - init system           sysvinit -> systemd
> - network               ifcfg    -> wicked
> ...
>
> The "logic" how to migrate things is built into YaST (and
> AutoYaST / AutoUpgrade) respectively, and we do cover
> migration of bootloader, init system, network and more
> with this (YaST based) migration path.
>
> We hesitated to support an inplace migration from ext3 to
> btrfs for the "/" filesystem, though, and we are not
> supporting it. Why?
> 1. The inplace migration of ext3 to btrfs requires some
>    free space on the source file system.
> 2. The inplace migration only works for ext3 filesystems
>    which have been created with specific options; this
>    for example does not always work for filesystems
>    created by SLES 10 and early versions of SLES 11.
> 3. The disk partitioning must be prepared to have space
>    for the Grub2 first- and second-stages. This is not
>    true for all partitionings created with older SLES
>    versions (including early SLES 11 versions).
> 4. People who are thinking about migrating "/" to btrfs
>    most probably want to do so, to enable snapshot/
>    rollback as the _real_ benefit.
>    For _this_ to work, though, you would get rid of the
>    the "/boot" partition, as for rollback to work
>    "/boot" must be on the same file system as "/",
>    and it not even can be a btrfs subvolume, ...
>
> Now, if "/" would be a migratable ext3 filesystem and if
> it would have enough space and even enough space to cover
> /boot, and if the bootloader pieces would fit on the disk,
> and if you would be able to run an AutoYaST profile on it,
> to help migrating the other stuff mentioned above, ...
>
> => Too many "ifs". Too many ifs to test this, and too many
> ifs to make this reliably working and supported.
>
> > I know that you can do an "in place" migration from
> > SLES11 to SLES12 I know that you can do an "in place"
> > migration of ext3 (the SLES11 default) to BTRFS (the
> > SLES12 default)
> >
> > Done correctly an in-place SLES11 => SLES12 should
> > produce a server that is indistinguishable from a clean
> > install of SLES12 (except for retaining data etc)
>
> I agree that as a "manual" process you might be able to
> migrate a SLES 11 SP3 system to SLES 12 this way.
>
> It's an error prone process, and you may end up losing
> data, e.g. if you have to re-partition to create space
> for the Grub2 bootloader pieces on your disk.
>
> However,let's think about what you really want. Let's
> start more theoretically ...
>
>
> II. How you may achieve (soon) what you are looking for
>
> You want a SLES 12 system, with snapshot/rollback for the
> "full system" without the need to reconfigure and tweak
> everything you did configure and tweak for SLES 11.
>
> Is this the correct understanding?
>
> > How do you set up the other "default" BTRFS
> > sub-volumes and how do you move/migrate the existing
> > subdirectories into the default BTRFS sub-volumes.
> >
> > Is there a migration tool/script that would help to
> > "complete" the ext3 => BTRFS migration process?
>
> If yes, there are obviously two ways to achieve your goal:
>
> 1. In place migration; as discussed above, and not
>    supportable / not supported.
>
> 2. A way to preserve your complex configurations (which
>    you did in SLES 11 ) and re-apply them on SLES 12.
>    Some tool, which
>    - "inspects" your SLES 11 system
>    - "validates" and normalizes your SLES 11 configuration
>    - allows you to "show" and change the configuration
>    - helps you to "build" a SLES 12 system based on your
>      (former) configuration (using KIWI).
>
> Do you remember the steps of "inspect" / "validate" /
> "show" / "build"?
>
> It's what the tool "machinery" in the "Advanced Systems
> Management Module" is meant for. And while the tool is not
> fully there yet, where we want it to be, it is the most
> promising way of migrating complex configurations between
> operating system versions or even operating systems going
> forward.
>
> Hope this helps to explain SUSE's plans in this area.
>
> So long -
>         MgE
>
> --
> Matthias G. Eckermann     Senior Product Manager   SUSE® Linux Enterprise
> Phone: +49 30 44315731    Mobile: +49 179 2949448    E-Mail: mge at suse.com
> SUSE LINUX Products GmbH  Maxfeldstraße 5          90409 Nürnberg Germany
> GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer, HRB 16746 (AG Nürnberg)
>
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