Relocatable Derivations

Published 2026-06-08 on Farid Zakaria's Blog

The earlier post on guix-transfer highlighted how we can use the tool to transfer derivations from /gnu/store to /nix/store.

It is always delightful when someone offers deeper insights into an idea I had put forward.

I was so focused on the transfer from derivations from Guix, I failed to see the larger applicability of the tool.

@tomberek shared with me the insight that the tool can be generalized to: “transfer derivations between realms”.

Relocatable derivations. 💥

What does that mean?

Perhaps the clearest concept to apply it to are deployments.

You might have a derivation FooBar.drv that you want to propagate through cascading deployment tiers: alpha, beta, and prod.

You might have needed to painstakingly apply some logical firewall if all three realms used /nix/store as their prefix to gate your deployment.

By changing the prefix of each one, i.e. /beta/store or /prod/store, they are naturally segregated in Nix.

How do we promote derivations from one realm to another?

We could re-evaluate the Nix expression again against each new store or we can leverage guix-transfer.

Why is this better than doing NIX_STORE_DIR=/prod/store nix-instantiate against these new store directories?

What is our source of truth? The Nix files or the derivations?

I posit that the derivations themselves are the source of truth.

Furthermore, evaluation could be slow and requires the full source code (Nix expressions) and the entire evaluation environment (i.e. Nixpkgs, plugins, and overlays).

By relocating at the derivation level, we move from Evaluation-based deployment (which is slow, requires source access, and may be prone to evaluation-time impurities potentially) to a Plan-based deployment.

We now treat the build graph, via the derivations, as a portable artifact that can be relocated into any realm, regardless of whether that realm has the source code, the right version of Nixpkgs, or in the case of Guix, even speaks the same front-end language.

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