Aaxtomp3 only looks available


I am able to find a package:

nix search nixpkgs aaxtomp3
* legacyPackages.x86_64-linux.aaxtomp3 (1.3)
  Convert Audible's .aax filetype to MP3, FLAC, M4A, or OPUS

but not able to install it:

building Nix...
building the system configuration...
error: undefined variable 'aaxtomp3'

       at /etc/nixos/configuration-supplement.nix:148:5:

          148|     aaxtomp3
             |     ^
(use '--show-trace' to show detailed location information)

What’s going on?

It is only available on unstable, not on 22.11. You probably need a nix-channel --update.


Thanks @wamserma! I am surprised because I expected nix search to provide an introspection of the current system. What options do I have to install the package beside moving to unstable (nix-channel update didn’t help)?

If you do nix search nixpkgs whatver nix first updates it’s flake info on the given channel (here: nixpkgs), then searches for whatever.

You can add the release channel to the registry, then tell search to use this flake.

Edit: In my home-manager config I have:

nix.registry = {
       nixos = {
         from = { type = "indirect"; id = "nixos"; };
         flake = args.nixpkgs;

so I can do nix search nixos whateer and it will match what is available on my current system.

Edit2: If you only need the tool occasionally, you don’t need to install it at all, just use nix run nixpkgs#aaxtomp3 or nix shell nixpkgs#aaxtomp3. Otherwise, see the reference given by @nixinator below.

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Nix is the art of containers without actually using containers.

You can mix unstable and stable packages quite easily on your system without fear of getting your system into a unrecoverable mess.

In this case you have aaxtomp3 from unstable, and leave the rest of your system on stable.

@TLATER has a in depth explanation of this. Installing multiple packages from unstable channel in configuration.nix - #2 by TLATER

I’d avoid using nix-env to do it, and just do it from your system configuration.

If your using flakes for your system configuration , it’s even easier to add an inputs to stable and unstable nixpkgs, and pull in packages from both.

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as the package maintainer for aaxtomp3, I would also be happy to packport it for stable; just forgot for this one.


we went from, problem, to possible solution, to package maintainer back porting it to stable which will be available shortly.

Now that is what i call customer success.