View source for Building ancient nixpkgs

Nix's reproducibility allows for easy building of ancient nixpkgs checkouts.

An attempt to get firefox 2.0 running can be found here: https://github.com/ronthecookie/nixpkgs/commits/2007-fixing 

== Replacing outdated nix.cs.uu.nl ==

You may find that the build fails as it cannot find some tarballs. This is solved by updating the primary mirror URL to one that is still running:
<syntaxhighlight lang="shell">
for x in $(find); do sed -i 's/nix.cs.uu.nl/tarballs.nixos.org/g' "$x"; done
for x in $(find); do sed -i 's/dist\/tarballs\///g' "$x"; done
</syntaxhighlight>

You will also want to run <code>nix-build</code> with the <code>--no-substitute</code> flag to avoid any outdated caches.

== Replacing outdated package sources ==

<code>nix-build</code> may fail while trying to fetch a package from a 3rd-party mirror. 
If this happens, you will need to search the internet for another mirror from which you can fetch the package; for certain nixpkgs versions you will need to ensure it does not force-redirect to SSL as <code>curl</code> was not built with SSL support in early versions.

You can manually add a tarball to the store by using <code>nix-prefetch-url</code>. You have to use the same checksum algorithm used in the nixpkgs definition with the <code>--type</code> parameter.

 [[Category:Cookbook]]