(Re)configuring an existing client (was: "clone" an example client?)

[Toomas Tamm]

On Thu, 2011-12-08 at 12:20 +0100, SYSTEMS Oliver Osburg wrote:

> I often reconfigure my clients, too. Config Files change, and I also 
> would appreciate a way to "automatically" create FAI configs from a 
> running Debian Machine. But in a way, this violates the FAI philosophy 
> "Do all configurations on the server".

I would recommend looking at system configuration tools, such as
cfengine and puppet (possibly there are others which I am not aware of).
We use cfengine version 2 (version 3 is different in highly incompatible
ways, so you better pick one and stick with it).

All, even the tiniest differences between a system "as installed" and
the system "as configured" are recorded in the cfengine (or puppet, if
you prefer that tool) configuration files. The configuration trees
themselves are kept in a versioning system (we use Subversion here). It
seems like a huge effort to set up initially (and it is), but the
benefits will outweigh the initial cost by many times in the future.

During the last stages of FAI installation, the configuration is
obtained from the versioning system and applied with the cfengine. Among
the configurations are instructions for cfengine itself to keep the
machine up-to-date in the future. All future changes in configuration
are done in the instructions to cfengine. Thus they get applied in
similar manner both to existing systems, as well as new ones when those
will be installed in the future.

One extra benefit of keeping the configuration in Subversion is the
possibility to merge changes to configuration files made by the OS
vendor(s) (Debian in our case). This way I never need to worry about
losing changes at upgrades.

We use somewhat customized FAI softupdates to keep package lists on
hosts in sync, but I believe that could be automated with the
configuration tools as well.

Finally, read http://www.infrastructures.org/ . I think this is the
single most useful site which has influenced the way I look at systems
management, even though they never mention FAI or cfengine, and the site
has not been updated for years.

-- 
Toomas Tamm                                 e-mail: tt-fai (at) kky.ttu.ee
Chair of Inorganic Chemistry                voice:  INT+372-620-2810
Tallinn University of Technology            fax:    INT+372-620-2828
Ehitajate tee 5, EE-19086 Tallinn, Estonia  http://www.kk.ttu.ee/toomas/