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Re: cfengine ideology question


From: Mark . Burgess
Subject: Re: cfengine ideology question
Date: Thu, 15 Apr 2004 08:54:19 +0200 (MEST)


On 14 Apr, Lev Lvovsky wrote:
> One of our administrators up and left from work recently, so it's 
> getting even more important that we get something like cfengine up and 
> running (the process has been sidelined by many other things sadly).
> 
> I realize that cfagent can execute scripts on a box, but from an 
> ideology perspective, is this a bad idea?  One of the main reasons that 
> we would use cfagent is to run scripts at designated times, or 
> depending on certain circumstances (software release etc...) - is it 
> generally done so that you use the functionality of cfagent/cfengine to 
> run stuff with its own built-ins, or are external scripts just as 
> welcome in its use?
> 
> thanks,
> -lev

Hi Lev,

I am not keen on words like "ideology". I think that if a tool has
nothing more than ideology going for it then it's probably not
worth much. But there is always a reason for what is best.

The advantage of cfengine actions is their predictable behaviour
and reproducibility, so it is best to use them if possible. 
However, cfengine does not make very specialized script writing easy
and it is therefore necessary to call other scripts within the cfengine
framework. That allows you to
 - keep everything in one place
 - organize the script runs in relation to other config stuff
 - borrow some of the safety features of cfengine

Recently "methods" were introduced in cfengine to allow more
complex behaviours in cfengine scripts, but even with these there
will be times when your own script is better.

So my answer:
- if cfengine makes it reasonably easy, there are sound reasons
to use cfengine actions.
- if cfengine does not give you the flexibility, or its discipline
is too stringent, then use your own script.

What people often do "wrong" in my opinion is to be too quick
to abandon the cfengine actions for their own scripts, because
they are unfamilar with the manual. That means they waste the
features that are there to help them.

I have promised to hold and "advanced tutorial" at LISA04 on cfengine
in addition to the beginners' tutorial.

M

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