How to include a package from another channel?

Help
1

I wanted to use Terraform 0.13.4 so I wanted to get it from nixos-unstable channel.
I’ve added the channel like so:

 > sudo nix-channel --add https://nixos.org/channels/nixos-unstable nixos-unstable
 > sudo nix-channel --list                                                        
nixos https://nixos.org/channels/nixos-20.09
nixos-unstable https://nixos.org/channels/nixos-unstable

And I tried getting the package using import:

  unstablePkgs = import <nixos-unstable> { };

But when I try to build that I get an error:

error: file 'nixos-unstable' was not found in the Nix search path (add it using $NIX_PATH or -I), at /etc/nixos/roles/work.nix:6:25

My $NIX_PATH looks like this:

 > echo $NIX_PATH | tr ':' '\n'
/home/jakubgs/.nix-defexpr/channels
nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixos
nixos-config=/etc/nixos/configuration.nix
/nix/var/nix/profiles/per-user/root/channels

And I can see that the channel is there in the first path:

 > ls -l /home/jakubgs/.nix-defexpr/channels/
total 2
lrwxrwxrwx 1 root root  60 Jan  1  1970 manifest.nix -> /nix/store/dkcsmb9gc5r43g97l1wbhz2qhxrz7lj5-env-manifest.nix
lrwxrwxrwx 1 root root  78 Jan  1  1970 nixos -> /nix/store/f227g1ph32pxl06h71x9aair6z65syc6-nixos-20.03.3129.d3784204ba1/nixos
lrwxrwxrwx 1 root root 100 Jan  1  1970 nixos-unstable -> /nix/store/liasszqdxazz50b7i15lmzjifyazjm16-nixos-unstable-21.03pre246543.24c9b05ac53/nixos-unstable

So I’m not sure what I’m missing to make this work.

2

What I found out is that if I use the -i flag - which stands for --login and adds user env too, in this case that of root - with sudo makes it work:

sudo -i nixos-rebuild switch --upgrade
3

Example: /etc/nixos/unstable-packages.nix:

{ config, pkgs, ... }:
let
  baseconfig = { allowUnfree = true; };
  unstable = import <nixos-unstable> { config = baseconfig; };
in {
  environment.systemPackages = with pkgs; [
    unstable.terraform_0_13
  ];
}

OR (as user):

nix-env -iA nixos-unstable.terraform_0_13
1 Like
4

Oh, interesting point. I forgot that doing a separate import would not include allowUnfree. But right now I have Terraform installed without providing that in config and it still works. So not sure if that’s necessary.

5

You have added the channel as your user, though you rebuild the system as root, you should add the unstable channel to your roots environment using sudo nix-channel --add https://nixos.org/channels/nixos-unstable nixos-unstable.

Also, to avoid warnings about that channel name beeing used twice, you should remove it from your user.

6

Except I didn’t It was added as root. See my post, I used sudo for nix-channel commands.

EDIT: It was actually added as both, since I thought that was an issue beforehand.

7

Indeed, I was just confused by the fact that it worked with passing in the users environment.

Have you run sudo nix-channel --update after adding the channel?

The channel isn’t available without it…

By running sudo -i nixos-rebuild switch --upgrade (which implies a nix-channel --update) you might even have caused that nix updated and created the channels in your users environment.

8

Yeah. It’s weird. But what’s even weirder is that I did nix-channel --update without sudo and now sudo nixos-rebuild switch --upgrade works without the -i.

I really don’t get how that nix-channel --update fixed anything since as you can see in my OP the channel symlinks were clearly visible in the /home/jakubgs/.nix-defexpr/channels folder.

9

I’m not 100% sure but I think nix-channel --update without sudo fixed it.

But why? How? No idea.

10

They are within your users folder, which nixos-rebuild should not respect, but you forced it to, by using sudo -i. That together with the implied update of the channels probably confused the system.

11

No, as I stated before, the channels were added BOTH for me and root.

12

You have never shown roots defexpr, and that’s where nix channel would create them.