Re: 1st unpacking, 2nd dependency checking
On Thu, 8 Oct 1998, Martin Schulze wrote:
> This might be an faq.
>
> But occasionally I notices that dpkg first unpacks and installs
> the files in a particular package and checks dependencies afterwards.
>
> This means that wrong dependencies are discovered when it is
> too late since the old version of the package is already
> overwritten.
>
> I'm sure there is a rationale for this, but what is it?
The rationale is that this would make package installing too much
troublesome, if not impossible in some cases. In particular, if A depends
on B and B depends on A, you would be unable to install A and B at all.
With the current design, you can.
> At least I would have expected that dpkg tests the dependency
> of new packages and refuses to unpack them - unless one told
> it to ignore dependencies.
This is exactly the case for Pre-Dependencies, and that's the reason
why essential packages need Pre-Dependencies as a general rule (we can not
afford to have them broken at *any* time).
For non-essential packages, the user is supposed to be able to use the
packaging system (dselect, dpkg, etc.), which is supposed not to be broken
thanks to the Pre-dependencies, to satisfy any remaining broken
(not Pre-)dependencies.
--
"f1d425529e79e6faba09bd7e97315457" (a truly random sig)
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