[Nix-dev] Understanding the Binary Cache

[Herwig Hochleitner]

2016-03-06 2:50 GMT+01:00 Roger Qiu <roger.qiu at matrix.ai>:

>
>

Oops, I replied off-list by accident. Maybe somebody can detail on the
follow-up.


> So if the upstream URLs are failing, does that mean building from source
> is impossible, or is building from source is still possible, but I didn't
> enable it? (You mentioned building from source is by default false).
>

That's what --fallback is for

Do you have links to issues/mailing list discussions about the transition
> between binary caches and binary manifests?
>
>
On 5/03/2016 2:57 AM, Herwig Hochleitner wrote:
>
> 2016-03-03 8:56 GMT+01:00 Roger Qiu <roger.qiu at matrix.ai>:
>
>>
>> I am just trying to understand this. If this is true, then why is it
>> that when I sometimes try to install packages, the installation process
>> fails because the upstream URL is not responding. This has happened
>> several times on 15.09 with different kinds of packages like Sage,
>> packages from Freedesktop.org... etc.
>>
>
> It tries to find the package in the binary cache anyway. This behavior is
> governed by multiple flags (man 5 nix.conf), amongs other:
>
> build-use-substitutes (default true) => try to use binaries
> build-fallback or --fallback (default false) => build from source, if
> binaries exist but fails (e.g flaky connection)
> [binary- / extra-binary- / trusted-binary- ] caches => set binary caches
> to be used
>
> I understand that there are certain packages that always need to be
>> built from source like the nvidia binary blob. But those above packages
>> shouldn't have problem right?
>>
>
> That should happen on demand.
>
> Anyway I'm looking for a way to find what binaries are actually
>> available in the binary cache ahead of time, and compare them between
>> the main channels and the small versions. I've looked around and I can't
>> find anything that actually states the binaries available in small
>> channels versus the main channels.
>>
>
> This area is currently in transition: binary-caches are being obsoleted in
> favor of binary manifests:
> <https://nixos.org/releases/nixos/unstable/nixos-16.03pre77568.40c586b/MANIFEST>
> https://nixos.org/releases/nixos/unstable/nixos-16.03pre77568.40c586b/MANIFEST
> Those are pretty greppable and you can use them directly from command
> line, I forget how ...
>
> BTW, you can run a git checkout and still enjoy the benefit of prebuilt
> binaries, by sticking close to the most recent channel commit:
> https://github.com/NixOS/nixpkgs-channels/tree/nixos-unstable
>
>
> --
> Founder of Matrix AIhttps://matrix.ai/+61420925975
>
>
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