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This post does not do Nix justice, as it only references the extensional model of Nix. In the PhD of Eelco Dolstra, the extensional model (chapter 5) describes

This post does not do Nix justice, as it only references the extensional model of Nix. In the PhD of Eelco Dolstra, the extensional model (chapter 5) describes derivations with identity based on their inputs, while the intentional model (chapter 6) describes derivations with identity based on their outputs [1]. Due to the complexity of the intentional model, the extensional model has been the initially used one. The upgrade to content addressed derivations is ongoing (see blog posts via Tweag for an intro [2]). > Neither Nix or NixOS gives you these guarantees. With content addressed derivations you can guarantee that any party can recreate bit-by-bit identical copies of derivations, meaning that Nix can guarantee reproducibility. Beta testing of content addressability in Nix started in May 2021 [3]. [1] https://edolstra.github.io/pubs/phd-thesis.pdf https://edolstra.github.io/pubs/phd-thesis.pdf [2] https://www.tweag.io/blog/2020-09-10-nix-cas/ https://www.tweag.io/blog/2020-09-10-nix-cas/ [3] https://discourse.nixos.org/t/content-addressed-nix-call-for-testers/12881 https://discourse.nixos.org/t/content-addressed-nix-call-for...

Foxboron 2y ago
> With content addressed derivations you can guarantee that any party can recreate bit-by-bit identical copies of derivations It wouldn't guarantee anything. It would force you, and anyone else, to do massive rebuilds when some binary down the tree changes, or has a regression.
- pveierland 2y ago
  My writing was imprecise, I meant to communicate that it makes it possible to trust the contents of a derivation, given that you know that the hash is correct, which can be verified independently in the cases where the derivation is reproducible. Content addressability makes it easier to establish and verify trust across systems. Given the degree to which the post is referenced, I do feel that it misses out by only describing input addressed derivations and not CA.

Foxboron 2y ago

> With content addressed derivations you can guarantee that any party can recreate bit-by-bit identical copies of derivations It wouldn't guarantee anything. It would force you, and anyone else, to do massive rebuilds when some binary down the tree changes, or has a regression.

pveierland 2y ago
My writing was imprecise, I meant to communicate that it makes it possible to trust the contents of a derivation, given that you know that the hash is correct, which can be verified independently in the cases where the derivation is reproducible. Content addressability makes it easier to establish and verify trust across systems. Given the degree to which the post is referenced, I do feel that it misses out by only describing input addressed derivations and not CA.