Nix: Managing multiple channels

This post will document how to add multiple channels for the Nix package manager and the way to install (or do any other operations) specific software from a particular channel.

First, go to this url to find out the specific channel which you want to add. Since by default nix adds the unstable channel, I will add up the stable channel for my profile. Note that the stable channel will be the latest nixos package version. After finding it’s url, add it like this:

$ nix-channel --add https://nixos.org/channels/nixos-14.12

And then update it:

$ nix-channel --update nixos-14.12

Now this will update and download the related nix package expressions related to it. To see the actual downloaded path, you can do something like this:

    sibi::monoid { ~ }-> cd ~/.nix-defexpr/        
    sibi::monoid { ~/.nix-defexpr }-> ls
    channels
    sibi::monoid { ~/.nix-defexpr }-> cd channels
    sibi::monoid { ~/.nix-defexpr/channels }-> ls
    binary-caches  manifest.nix  nixos-14.12  nixpkgs
    sibi::monoid { ~/.nix-defexpr/channels }-> cd nixos-14.12
    sibi::monoid { ~/.nix-defexpr/channels/nixos-14.12 }->
    sibi::monoid { ~/.nix-defexpr/channels/nixos-14.12 }-> ls
    default.nix  nixos  nixpkgs  programs.sqlite
    sibi::monoid { ~/.nix-defexpr/channels/nixos-14.12 }-> cd nixpkgs/
    sibi::monoid { ~/.nix-defexpr/channels/nixos-14.12/nixpkgs }->

Note that the nixpkgs directory above under the channels directory contains expressions for the unstable channel. Now to install or search package from that stable channel, you can do something like this:

$ nix-env -f nixpkgs_channel_directory -iA package_name

which can be something like this:

$ nix-env -f ~/.nix-defexpr/channels/nixos-14.12/nixpkgs/ -i firefox

for installing from the stable channel.

Thanks to Lethalman from #nixos for pointing me to the right direction.