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Re: [custom] Custom Debian Distros need the help from debian developers

El Tue, Mar 09, 2004 at 12:09:13PM +0100, Conrad Newton escribi� From Benj. Mako Hill on Tuesday, 2004-03-09 at 01:24:33 +0100:
> > On Thu, Mar 04, 2004 at 12:45:12AM +0100, Free Ekanayaka wrote:
> > > Andreas,  I've read again your paper  and I've just  noticed that your
> > > are referencing #186085 (maybe the first time I was too tired, or it's
> > > newly added).
> > 
> > I don't really think this is particularly important.
> > 
> > The way I see it, CDDs have two major problems: custom package
> > selection and custom package configuration. This thread has already
> > talked about custom package configuration in regards to pre-seeding low
> > priority (or even unasked) debconf questions. IMHO, custom package
> > selection (the problem that #186085 seems to be addressing) is an
> > easier and less pressing problem.
> Hear!  Hear!  The question of custom package configuration is one
> of the big problems, and not discussed often enough, in my opinion.
> Let us assume that all of Klaus Knopper's packages had been put
> into Debian already---you would _still_ not be able to install
> his system to create your own Knoppix using the Debian installer, 
> because you would not have his configuration.

  Right, for this you need the equivalent of a tarball of his '/etc/'
  files, but the problem with the tarball is that it is not upgradable
  (we can't assure the configuration files would be right for future
  versions of the packages) and is directly related to the full set of
  packages installed (if you want a different set of packages you will
  have configuration files for uninstalled packages).

> If we generalize this question slightly, I would like to ask
> why it should not be possible for me to get an exact copy of
> your system through the apt-get mechanism.  Of course you can
> send me your package list, and I can install all the packages,
> but I think we all agree that my system will differ from yours 
> significantly---despite the identity of packages---because of 
> differences in configuration.
> What needs to be done to enable me to make an identical copy,
> modulo differences in hardware, via apt-get?

  Well, in the first place I must say that what you want is a way to
  'clone' a system, and that is usually done using other tools different
  than apt-get.

  Anyway, if you want to be able to do it using apt-get we need to
  develop a system that can extract the relevant information of an
  installed Debian system and packages this information. To do this we
  - A way to get the debconf answers from your system (already
    available) *and* verify that those answers can be used to generate
    the same configuration files from the installed package. If that is
    possible, this part of the configuration data should be
  - For config files not generated by debconf we have to verify if the
    files have been modified. If the answer is yes, we have to identify
    to which package(s) each file belongs to (with its version number)
    and build a set of configuration packages that can be installed
    after the corresponding packages are installed. The problem with
    this is that once the package is upgraded we can't assure that the
    config file is valid (we could try to include this information on
    new packages, letting them declare that it accepts previous
    configuration files, but I see a lot of problems with this ...).

  - A way to identify user generated configuration files; once they are
    identified we will treat them as we do with hand modified
    configuration files.
  I don't think this makes sense, and in fact I belive that the aproach
  taken by current CDDs like debian-edu is just the opposite; instead of
  extracting the configuration from an installed system the answers to
  debconf questions are generated by hand and for config files that
  can't be configured this way they use handmade cfengine scripts.
  What I don't know is how good is cfengine for upgrades, mainly because
  I've never used it ... ;(

Sergio Talens-Oliag <sto@debian.org>   <http://people.debian.org/~sto/>
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