[Nix-dev] dead sources

[Shea Levy]

On Jan 6, 2013, at 13:19, Mathijs Kwik <mathijs at bluescreen303.nl> wrote:

> On Sun, Jan 6, 2013 at 6:10 PM, Michael Raskin <7c6f434c at mail.ru> wrote:
>>> But instead of just having to wait for a while, the whole experience
>>> was a lot less pleasant, as the build process errored out every hour
>>> or so, because of missing source downloads. As I was not present the
>>> whole time, but only check/fix/restarted occasionally, I'm not even
>>> halfway done yet :(
>> 
>> I guess specifying -k (--keep-going) flag to nix-build would help.
>> 
>> nix-build /etc/nixos/nixos -k -A system
> 
> Didn't think of that, but it might indeed get me a bit further.
> Depends a bit on how high/low in the dependency-tree the missing
> source sits though.
> For example if some X11 source is not found, building anything
> graphical will be skipped.

But the sources for the graphical stuff will still be downloaded

> 
>> 
>>> I think it's important to be able to build nixos/nixpkgs fully from
>>> source, or at least know upfront if any download-related errors will
>>> occur.
>>> I can think of 3 ways which could improve the current situation.
>>> 
>>> a) --download-only option for nix-build
>>> That way, before attempting long builds, I can make sure I have all
>>> the sources, and don't even need an internet connection during the
>>> real build.
>> 
>> I am not sure how the flags get passed around inside...
>> 
>> Right now you could use nix-reduce-build script inside nix repository...
>> Among its functionality is
>> 
>> nix-reduce-build /etc/nixos/nixos:-A:system -- nix-self-fixed://
>> 
>> It is not installed by default because it can do so many things that its
>> precise purpose is unclear.
> 
> Didn't know about it. Looks like a useful tool :)
> 
>> 
>> It looks like NixOS system refers to some downloads that are not needed
>> even when building from near-scratch (and so some failures from
>> nix-reduce-build are not significant), but it keeps trying the remaining
>> things on single failures so it downloads whatever it is possible.
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