FAQ/nixpkgs

Question: When I do an import <nixpkgs> {}, which channel or path gets imported.

Answer:

Use nix repl '<nixpkgs>' on shell and then enter path in the repl to know what nixpkgs is currently being used.

Nix tools use $NIX_PATH to decide which path to use in the import call. The first entry in that variable is typically <userhome>/.nix-defexpr/channels. If a user has explicitly added a channel named nixpkgs, then that channel is used in the import <nixpkgs> call. Otherwise, the nixpkgs= named entry is used for the import <nixpkgs> call. To have <nixpkgs> represent the same version of nixpkgs as your system flake, you can set nix.nixPath = [ "nixpkgs=${inputs.nixpkgs}" ]; in your system flake.

Some tools don't fully respect $NIX_PATH and instead search ~/.nix-defexpr so there might be some unexpected behavior.