bug#21784: Old XZ tarballs

[ludo@gnu.org (Ludovic Courtès)]

Lasse Collin <lasse.collin@tukaani.org> skribis:

> On 2015-11-01 Ludovic Courtès wrote:
>> Lasse Collin <lasse.collin@tukaani.org> skribis:
>> 
>> > On 2015-10-30 Ludovic Courtès wrote:
>> 
>> [...]
>> 
>> >> Guix does automatically mirror tarballs via its “substitute”
>> >> mechanism. However, users can turn it off, in which case they end
>> >> up downloading the tarball from the upstream URL specified in the
>> >> package recipe.
>> >
>> > OK. :-) Why would users turn it off though?
>> 
>> The substitute mechanism is very generic; it’s not just about
>> mirroring tarballs:
>> 
>>   http://www.gnu.org/software/guix/manual/html_node/Substitutes.html
>> 
>> Some people might prefer to build things locally rather than download
>> pre-built items.
>
> That makes sense, but I don't understand how it implies that the source
> packages will then be downloaded from upstream servers.

It might sound counter-intuitive, but our server at gnu.org provides
substitutes for “things” users could do locally; these “things” include
building software, and downloading source.  Quoting the above page:

  Substitutes can be anything resulting from a derivation build (see
  Derivations). Of course, in the common case, they are pre-built
  package binaries, but source tarballs, for instance, which also result
  from derivation builds, can be available as substitutes.

> Anyway, I'm sorry for the hassle and for perhaps making a mountain out
> of a molehill.

No problem.  It is best if URLs remain stable over time, but I
understand there are cost constraints related to hosting.

Maybe an option for you in the longer term would be to use a service
such as savannah.gnu.org, which could host tarballs virtually forever
and which is mirrored.

Thanks,
Ludo’.