Re: Version Woes

[Frank Crawford]

On Thu, 2020-04-30 at 14:17 -0400, Derek Atkins wrote:
> Hi Eric,
> 
...
> Honestly I don't know if we've agreed on any objectives.  I can state what
> mine is, which I hope is somewhat non-controversial:
> 
> * Ensure that someone installing a modern OS can continue to backup
> existing servers running older software (e.g. 1.2.8), with the assumption
> that the older software cannot be upgraded.
> 
> That's my objective.  I see two ways to do this:
> 
> 1) Get an rdiff-backup-{2/3} that can talk to rdiff-backup 1.2.8

This can't happen ever, as the difference is at the python level, not
with rdiff-backup.  This would almost be a bigger project than porting
rdiff-backup from python2 to python3.

> 2) Supply both rdiff-backup-2 and rdiff-backup1 simultaneously as OS
> Packages, possibly with some glue to detect the wire format and
> automatically switch between them.

There are two different requests you have here, having the two versions
on a host at the same time, and something will happen about that
shortly, although it isn't just rdiff-backup but also the dependencies
like pylibacl and pyxattr.  Some of which don't even currently exist in
EPEL8 for example.

Shortly, as in weeks, there will be a version of rdiff-backup 1.2.8
available from my COPR repository, but that will never get back into
any of the official channel, because they won't be accepted.  Also
remember that this needs to cover EPEL as well as Fedora, and EPEL
versions will last far longer than any Fedora version.

In reality you also need to consider this for non-RHEL distibutions
too, but that is a question for the other distributions.

The second item is to automatically do this on the wire, and that is
only ever likely to be an unofficial package, as it real is only for
transition.

Now having said that, as you already have to have your backups scripted
somehow, even if it is just a shell that loops through a list of hosts,
you will need to make mods to choose one of the two versions during
execution.  This can be as simple as a two separate lists, or something
to make the choice on the fly, but there is no standard way to do this
within rdiff-backup, as it doesn't do any host selection currently.

> Honestly I'd prefer #1, but can live with #2.  Is there another approach
> to achieve the objective?
> 
> > Thanks, Eric
> 
> -derek

Regards
Frank