Re: Large-scale configuration backup with GIT?

From: Junio C Hamano <gitster@pobox.com>
Date: Sep 2, 2007, 21:49 UTC
Message-ID: <7vd4x0pwjm.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <20070902201724.GB10567@lug-owl.de>

Jan-Benedict Glaw <jbglaw@lug-owl.de> writes:

Show 13 quoted lines

> I'm just thinking about storing our whole company's configuration into
> GIT, because I'm all too used to it. That is, there are configuration
> ...
> In both cases, I'd be left with a good number of GIT repos, which
> should probably be bound together with the GIT subproject functions.
> However, one really interesting thing would be to be able to get the
> diff of two machine's configuration files. (Think of machines that
> *should* be all identical!)  For this, it probably would be easier to
> not put each machine into its own GIT repo, but to use a single one
> with a zillion branches, one for each machine.
>
> Did anybody already try to do something like that and can help me with
> some real-life experience on that topic?

This is something similar to what I and others in my group did long time before git was even invented. I'd suggest you go in the opposite direction.

If you have 5 configurations, each of which have 20 machines that _should_ share that configuration (modulo obvious differences that come from hostname, IP address assignment, etc), then

 - You keep track of 5 configurations; in git, you would
   probably maintain them as 5 branches.

 - You have a build mechanism to create systemic variation among
   20 machines that shares one configuration; this can be
   different per branch.  So if you have 20 solaris machines all
   should share logically the same configuration, you would:

	$ git checkout solarisconf

        ... tweak the config for machine #27, adjusting for
        ... hostname, IP address variation, etc...
        $ make target=solaris27 output=../solaris27.expect

   Make that makefile produce the output in named directory;

 - You get the config dump from your machines (your "staging
   area"), as you planned.  Then after running the above, you
   could:

	$ cd ..
        $ diff -r solaris27.expect solaris27.actual

   if your "staging area" for machine #27 is "solaris27.actual".

The difference you would see is something done by *hand* on the machine, which you would want to propagate back to the solaris configuration *source* you keep track in git. For some changes, you may even want to adjust that single manual change done on machine #27 so that you do not have to do that on other 19 solaris boxes manually, by adjusting the build procedure in the solarisconf branch.