[gentoo-dev] Re: etc-update & ._cfg* files: major issue with gentoo?

[kai.grossjohann@uni-duisburg.de (Kai Großjohann)]

"Dhruba Bandopadhyay" <dhruba@codewordt.co.uk> writes:

> When emerging packages configuration files beginning with ._cfg* are left
> in /etc and other locations and on subsequent emerges portage warns that
> one has X number of files remaining.  Now, on many occassions I have had
> several of these files on my system and have postponed dealing with them
> simply because they are a hassle.  Once in a while however, I use
> etc-update to sort them with care.
>
> There are many problems with the way this is done for a non-expert user
> (which may include myself) and the ones below are only a few of them.

I think part of the problem is the display of the differences.
Suppose you install a package for the first time which installs
version A of /etc/foo.  You change this file manually, giving version
B.  Sometime later you install a new version of that package which
comes with version C of the file.

Now if you ask etc-update for a diff, it shows you the differences
between versions B and C.  However, these differences partly stem
from the changes you made between A and B, and partly they depend on
the changes the upstream version had between A and C.

I think it would be more useful to show the differences between A and
C.  Then etc-update could ask whether these differences should be
integrated into the current version.  When the user says yes, then B
is patched with the A->C diff, giving a new version D.  (Or maybe C
should be patched with the A->B diff?  Probably it doesn't make a
difference.)  This process can introduce conflicts (if B and C changed
the same line).  Then users might have to resolve these conflicts.

Personally, I use cfengine to circumvent such problems: I never edit
config files manually, I just let cfengine do it for me.  Then, when
a new version of a config file is to be installed, I just tell the
system to install it, and then I run cfengine which incorporates my
changes into the new version.

This requires some thought when writing cfengine scripts.  You have
to anticipate in which way the syntax of the config file might change
and then design your editing operations so that they will still work
with the changed syntax.  Of course, when the config file syntax has
changed radically, then this automatic method will fail.  I guess
that if you design the editing scripts sensibly, then you will see
such failures easily.  (The program doesn't start because of syntax
errors, or the cfengine edit script complains it can't find anything
to edit.)

But even in the cfengine case, it would be useful to stash the
original versions of config files somewhere such that a diff between
A and C could be requested.

What do people think?
-- 
Ambibibentists unite!



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