[rear-users] REAR Versions Question

Johannes Meixner jsmeix at suse.de
Thu Jul 28 09:56:16 CEST 2016


Hello,

On Jul 27 15:52 Matthew Stavert wrote (excerpt):
> What happens if I use a higher rear version that my server.
> For example, what would happen if I used the rear 1.18
> for Sles 11 sp3, on a Sles 11 Sp2 server?

Basically anything could hapen - depending on
how you have set up your particular systems.

In general see
https://en.opensuse.org/SDB:Disaster_Recovery
in particular see therein the section
"Version upgrades with Relax-and-Recover (rear)"

Regarding SUSE's way to provide rear version upgrades
for SUSE Linux Enterprise (SLE):

For one product like SLE11 or SLE12 we provide several versions
in parallel so that users where version N does not support their
particular needs can upgrade to version M but on the other hand
users who have a working disaster recovery procedure with
version N do not need to upgrade. Therefore the package name
contains the version and all packages conflict with each other
to avoid that an installed version gets accidentally
replaced with another version.

Regarding backward compatibility:

In general rear 1.18 should be backward compatible
down to rear 1.16.
But rear 1.10.0 is totally different because since
rear 1.15 it has many new features and fundamental
changes. In particular the filesystem creation is
totally different (via the so called "layout workflow"
instead of the old "dr workflow" that has been removed
in rear 1.14).
But there is no guarantee that it really works
backward compatible in any case.
And "backward compatible" does not mean that one can
use one same rear config file /etc/rear/local.conf
for different products and service packs and architectures.
Each product / service pack / architecture may require
its own specific adaptions in /etc/rear/local.conf.
In sufficiently simple cases one same /etc/rear/local.conf
might even work from SLE11 up to SLE12-SP2 when
on SLE12-SP2 the same filesystem layout and bootloader
is used as on SLE11 in particular when neither btrfs
nor UEFI is used.
I.e. when the basic SLE12-SP2 system is the same as the
basic SLE11 system, then the same /etc/rear/local.conf
should work.
In short: New SLE12 GA / SP1 / SP2 features require
new specific adaptions in rear and /etc/rear/local.conf.
For some examples of such kind of special features see
https://github.com/rear/rear/issues/944
https://github.com/rear/rear/issues/556
https://github.com/rear/rear/issues/544

Regarding version upgrades from older rear versions:

Users who use btrfs and upgrade from our SLE12-specific
RPM package "rear116" to a newer rear version must
manually adapt their /etc/rear/local.conf file
because excluding btrfs subvolumes via EXCLUDE_RECREATE
was only needed in our SLE12-specific RPM package "rear116"
(with SLE12-specific adaptions for btrfs support)
but it leads to falsely excluded btrfs subvolumes from
the backup (and restore) for all newer rear versions
(i.e. since rear 1.17), see the GitHub issue 821
https://github.com/rear/rear/issues/821 in particular see
https://github.com/rear/rear/issues/821#issuecomment-215071027
This is a good example for what is documented in the section
"Rear Version Updates" in our SLE12-HA manual and online at
"Version upgrades with Relax-and-Recover (rear)" in
https://en.opensuse.org/SDB:Disaster_Recovery
that reads (excerpt):
  "For each rear version upgrade and for each change
   of a software that is used by rear you must carefully
   and completely re-validate that your particular
   disaster recovery procedure still works for you."


Kind Regards
Johannes Meixner
-- 
SUSE LINUX GmbH - GF: Felix Imendoerffer, Jane Smithard,
Graham Norton - HRB 21284 (AG Nuernberg)



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