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On Tue, 17 Feb 1998, Christian Schwarz wrote:
> On 16 Feb 1998, Manoj Srivastava wrote:
>
> I must admit I didn't notice this discussion until I saw the discussion
> about the bug reports on this topic. Could someone please explain in a few
> sentences the technical reasons behind this?
I will limit myself to repeat what I said in debian-devel:
Essential packages are supposed to work all the time, because they may be
used in any prerm, postrm, preinst or postinst script. And all the time is
*all* the time, not just between succesive runs of dpkg. Example:
Package A depends on library C, package B uses A in the preinst script.
A is essential. We issue the following command:
dpkg -i A.deb B.deb C.deb
Clearly, B's preinst will not work, because A is not configured yet.
This upgrade will be *much* safer by making A to Pre-Depend on C.
However, James Troup seems to think that there are two types of essential
packages, "essential" ones and "really essential" ones. I would like to
hear his opinion on this.
Of course I think there are just one type of essential packages and the
sole fact that a package is essential means that it may be used anywhere
in {pre,post}{inst,rm} scripts, which are also part of the packaging
system. I could not imagine a scenario in which a developer had
to think "no I can't use `ps' in my preinst because procps is only
essential, not `truly essential'". Anyway, if we are going to have two
types of essential packages, it should be documented somewhere...
BTW: I'm not sure that base-files should Pre-Depend on awk, because awk is
virtual and it is handled via alternatives. This means that you can't
both remove mawk and install gawk on the same dpkg run (currently, I'm
unable to find an example like packages A, B and C above for base-files
and awk which proves that the Pre-Depends is needed for base-files).
Perhaps we should just make mawk and gawk to Pre-Depend on libc6 instead?
Thanks.
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