Nix-channels / NIX_PATH
nixos-anywhere does not install channels onto the new system by default to save time and disk space. This for example results in errors like:
(stack trace truncated; use '--show-trace' to show the full trace)
error: file 'nixpkgs' was not found in the Nix search path (add it using $NIX_PATH or -I)
at «none»:0: (source not available)
when using tools like nix-shell/nix-env that rely on NIX_PATH
beeing set.
Solution 1: Set the NIX_PATH
via nixos configuration (recommended)
Instead of stateful channels, one can also populate the NIX_PATH
using nixos
configuration instead:
{
inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
# ... other inputs
outputs = inputs@{ nixpkgs, ... }:
{
nixosConfigurations.yoursystem = nixpkgs.lib.nixosSystem {
system = "x86_64-linux"; # adapt to your actual system
modules = [
# This line will populate NIX_PATH
{ nix.nixPath = [ "nixpkgs=${inputs.nixpkgs}" ]; }
# ... other modules and your configuration.nix
];
};
};
}
Advantage: This solution will be automatically kept up-to-date every time the flake is updated.
In your shell you will see something in your $NIX_PATH
:
$ echo $NIX_PATH
/root/.nix-defexpr/channels:nixpkgs=/nix/store/8b61j28rpy11dg8hanbs2x710d8w3v0d-source
Solution 2: Manually add the channel
On the installed machine, run:
$ nix-channel --add https://nixos.org/channels/nixos-unstable nixos
$ nix-channel --update