TurnKey Linux's take on Ubuntu appliance development: KISS

[Pau Garcia i Quiles]

On Tue, Dec 15, 2009 at 8:05 PM, Steve Langasek
<steve.langasek at ubuntu.com> wrote:
> On Tue, Dec 15, 2009 at 08:34:22AM -0500, Scott Kitterman wrote:
>> The bit of Debian policy that keeps getting quoted about packages not
>> modifying conffiles of other packages is incomplete.  It goes on to say ...
>            ^^^^^^^^^
>> except through defined interfaces.  There is nothing in Debian Policy that
>> prevents packages from being used for integration work.  It insists on
>> properly engineered work.
>
> Terminology is being conflated here.  "Conffiles" != "config files";
> "conffile" is the term used for a dpkg-managed config file shipped in the
> binary package, and it is *never* ok for a package to edit such a file,
> whether it's in the same package or in a different package, because it
> *will* result in prompts that the user didn't ask for and won't know how to
> resolve.

What's different with tkpatch? Meaning, how would those prompts be
different if those conffiles were managed by tkpatch instead of dpkg?
Let's see:

* With Debian packages:
  1. I install Postfix using Ubuntu packages (say, Karmic packages)
  2. I install the postfix-appliance-config package, which modifies
dpkg-managed files in the Postfix packages
  3. Some months later, I upgrade Postfix to a new version using
Ubuntu packages (say, Lucid packages). I will be presented with some
prompts for stuff modified by the postfix-appliance-config package.

* With tkpatch
  1. I install Postfix using Ubuntu packages (say, Karmic packages)
  2. TkPatch modifies dpkg-managed files in the Postfix packages
  3. Some months later, I upgrade Postfix to a new version using
Ubuntu packages (say, Lucid packages). I will be presented with some
prompts for stuff modified by the TkPatch tool

I see no difference. Or have I misunderstood the architecture of
TurnKey Linux and TkPatch?

Now, there is something nobody has said yet: order of installation.
That's the main difficulty I see with packages (and rest assured, I am
all for using packages to build appliances). AFAIK you cannot
guarantee in what order will apt install the packages, therefore it
might happen that postfix-appliance-config is installed before postfix
and, well, it won't work.

-- 
Pau Garcia i Quiles
http://www.elpauer.org
(Due to my workload, I may need 10 days to answer)