Nix Best Practices Flake Structure Standard flake.nix structure: Follows Pattern (Avoid Duplicate Nixpkgs) When adding overlay inputs, use follows to share the parent nixpkgs and avoid downloading multiple versions: All inputs must be listed in outputs function even if not directly used: Applying Overlays Overlays modify or add packages to nixpkgs: Handling Unfree Packages Option 1: nixpkgs unfree (Recommended for Teams) Use numtide/nixpkgs unfree for EULA licensed packages without requiring user config: This chains: proprietary tool → nixpkgs unfree → nixpkgs Option 2: User Config Users add to ~/.config/nixpkgs/config.nix : Option 3: Specific Packages (Flake) Note: config.allowUnfree in flake.nix doesn't work with nix develop use nixpkgs unfree or user config. Creating Binary Overlay Repos When nixpkgs builds a community version lacking features (common with open core tools), create an overlay that fetches official binaries. Pattern (see 0xBigBoss/atlas overlay, 0xBigBoss/bun overlay) Getting SHA256 Hashes Or use SRI directly: Dev Shell Patterns Basic Shell With Environment Variables Native Dependencies (C Libraries) Direnv Integration .envrc for flake projects: For unfree packages without nixpkgs unfree: Common Commands Troubleshooting "unexpected argument" Error All inputs must be listed in outputs function: Unfree Package Errors with nix develop config.allowUnfree in flake.nix doesn't propagate to nix develop . Use: 1. nixpkgs unfree input (recommended) 2. User's ~/.config/nixpkgs/config.nix 3. NIXPKGS ALLOW UNFREE=1 nix develop impure Duplicate Nixpkgs Downloads Use follows to chain inputs to a single nixpkgs source. Overlay Not Applied Ensure overlay is in the overlays list when importing nixpkgs: Hash Mismatch Re fetch with nix prefetch url and update the hash. Hashes change when upstream updates binaries at the same URL.

nix-best-practices