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Re: Overriding conf file with symlink under /etc considered harmful

First, I need a bit more clarification/confirmation that my understanding of
the challenge we're facing is correct, and then I'd like to see any prior
discussion & documentation (in the wiki?) we have on these issues (or help
write it if it doesn't exist yet).

On Sat, Apr 10, 2004 at 02:45:19PM +0200, Free Ekanayaka wrote:
> Well, maybe  a CDD configuration  package should be  not considered in
> the same way as ordinary packages.
> I think will  all agree that one of  the main goals  of a CDD, a  part
> from barely installing a specific subset of packages,  is to provide a
> properly tuned configuration for such subset.
> IMHO the  two best strategies  for this porpoise are:
> 1) feed  the   debconf  database  with custom  values  and  then   run
>    dpkg-reconfigure --all 

In prior discussions, is this what has been referred to as "pre-seeding"?  
What are the arguments to date for/against this?

> 2) use cfengine to directly tune or create configuration files
> AFAIK  these two methods were  both introduced by Skolelinux.
> The second one  is needed where the  first can't deal, and even though
> CDDs developers should  cooperate   with the maintainers   wherever is
> possible to introduce   or improve the  debconf  support for  a  given
> package, my opinion is that there will be  always cases which can't be
> cleanly handled with the first strategy.

Fair enough, but as much as possible, we try approach #1?

> A simple real life  example from DeMuDi: I  have to turn on the kernel
> lowlatency flag at boot time, and the best way to  do it is by editing
> /etc/sysctl.conf adding a single line (kernel.lowlatency = 1). 
> The sysctl.conf conffile belongs to the  procps package, but of course
> introducing the debconf support for all possible kernel variables it's
> not feasible, so that I ended up using the cfengine strategy.

I see.  I can't think of any decent alternative, either.  I'd like to see 
the prior discussion on this too, for reference.

> IMHO if someone wants to install a CDD, it means  that he/she wants to
> have  a pre-canned working    system, which  hopefully   automatically
> configures itself.
> Thus      when   installing    the      CCD   configuration    package
> (e.g. debian-edu-config, debian-med-config, demudi-confg, etc.),   the
> default answer   to the question "do   you want to  modify  this other
> package's conf file?" should be "yes".

Got it.

> I don't know if understand correctly, but  AFAIK when a new version of
> package  provides  a new version  for  one of its  conffiles *and* the
> previously  installed version of such  confile has been modified, then
> dpkg *do* stop asking if you want to keep the locally modified version
> or replace it with the new one.

Surely you mean only in the symlink case being discussed?  When a package
provides a new conf file and the old has been modified, dpkg will normally
prompt for whether you want to keep/replace the old.  But what I've been 
hearing earlier in this thread is that if the admin makes the conf file a 
symlink to another conf file instead of merely modifying the conf file, then 
this mechanism breaks.

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