Nix: attribute 'nixpkgs' in selection path 'nixpkgs.hello' not found

Created on 13 Feb 2018 · 25Comments · Source: NixOS/nix

Try running the following with Nix 2.0:

$ NIX_PATH=/nix/var/nix/profiles/per-user/root/channels nix run nixpkgs.hello
error: attribute 'nixpkgs' in selection path 'nixpkgs.hello' not found

This is different than how previous version of Nix worked.

Oddly settings 'nixpkgs' to anything in NIX_PATH (even something that doesn't exist) will fix this issue:

NIX_PATH='nixpkgs=asdf:/nix/var/nix/profiles/per-user/root/channels' nix run nixpkgs.hello

Source

matthewbauer

👍4 😕2

Most helpful comment

This is a major pain on macOS, which does not have a prefixed NIX_PATH, and only has the root channels by default. Same issue with the --daemon installation on Linux.

ElvishJerricco on 23 May 2018

👍3

All 25 comments

@edolstra Should this be supported? If not we need to update nix-profile.sh.in because it's using it:

https://github.com/NixOS/nix/blob/master/scripts/nix-profile-daemon.sh.in#L53

matthewbauer on 20 Feb 2018

This should be supported, because the manual still documents NIX_PATH as working this way (see Chapter 17).

lilyball on 28 Feb 2018

This is definitely a bug, not an intentional change. Will look into it.

shlevy on 3 Mar 2018

No, it's not a bug. Rather, the nix command does not have a replacement for channels yet, so it's currently left undefined where it gets its inputs from. (This is one of the main reasons why the nix CLI is marked experimental.) So currently it only uses prefixed NIX_PATH elements like nixpkgs=....

edolstra on 3 Mar 2018

@edolstra IMO it's definitely a bug at least that it works with a dummy nixpkgs= argument... #1942 fixes it too.

shlevy on 3 Mar 2018

How is it not a bug that the nix command is broken on a fresh install of Nix 2.0?

lilyball on 3 Mar 2018

How is it not a bug that the nix command is broken on a fresh install of Nix 2.0?

It also could be a bug in nix-profile-daemon.sh (which is only used by MacOS currently). See #1664 for a potential fix.

matthewbauer on 3 Mar 2018

Right, the Linux install script sets nixpkgs=$HOME/.nix-defexpr/channels/nixpkgs.

edolstra on 4 Mar 2018

Is there a concern with #1942?

shlevy on 4 Mar 2018

So currently it only uses prefixed NIX_PATH elements like nixpkgs=....

Has this behaviour changed?

@grahamc has tested NIX_PATH behaviour,

$ NIX_PATH=/home/grahamc/.nix-defexpr/channels nix build -f '<nixpkgs>' git

$ ls -la result                                                           
lrwxrwxrwx 1 grahamc users 54 Apr 3 08:32 result -> /nix/store/jaani1kx4a4kvz11d0myfkjjiiklfl7w-git-2.16.2

and it seems like the unprefixed NIX_PATH=/home/grahamc/.nix-defexpr/channels is still being used for evaluation?

tilpner on 3 Apr 2018

Is nix build actually a new command or is that just an alias for nix-build? Because the issue seems to be the new nix command stuff treats NIX_PATH differently than the existing commands, but if nix build is just an alias for nix-build then it stands to reason that you wouldn't see this issue with it.

lilyball on 3 Apr 2018

This is a major pain on macOS, which does not have a prefixed NIX_PATH, and only has the root channels by default. Same issue with the --daemon installation on Linux.

ElvishJerricco on 23 May 2018

👍3

It depends on the content of the NIX_PATH target folder:

$ ls /nix/var/nix/profiles/per-user/root/channels
binary-caches  manifest.nix  nixos

When NIX_PATH is just a path it will look up thinks from that folder. So in that case the channel doesn't contain nixpkgs and it will fail.

$ NIX_PATH=/nix/var/nix/profiles/per-user/root/channels nix repl
Welcome to Nix version 2.1.1. Type :? for help.

nix-repl> import <manifest.nix>
[ «derivation ???» ]

nix-repl> import <nixos>
«lambda @ /nix/store/syxm6jgcc0wj2qc7pg6vz44d5s9a42nc-nixos-18.09.1023.06fb0253afa/nixos/pkgs/top-level/impure.nix:15:1»

nix-repl> import <nixpath>
error: file 'nixpath' was not found in the Nix search path (add it using $NIX_PATH or -I), at (string):1:8

zimbatm on 3 Nov 2018

fixed in d7a84d330cc677d3c9e2c5553a861ab9f82245f6

matthewbauer on 25 Jan 2019

Not fixed actually

matthewbauer on 4 Sep 2019

Definitely broken. Updating to Nix 2.3 just broke nix run for me, since I'm not customizing my NIX_PATH.

lilyball on 9 Sep 2019

Quick hacky workaround that seems to be working for me on a Mac, based on @edolstra's comment above, is to prefix the command with NIX_PATH=nixpkgs=$NIX_PATH/nixpkgs, as shown below:

$ nix run nixpkgs.hello
error: attribute 'nixpkgs' in selection path 'nixpkgs.hello' not found
$ NIX_PATH=nixpkgs=$NIX_PATH/nixpkgs nix run nixpkgs.hello
[1 copied (0.1 MiB), 0.0 MiB DL]
bash-3.2$ exit

Seems to also fix nix search and nix eval.

Question to more knowledgeable people: should I put this NIX_PATH adjustment in my ~/.profile or something?

akavel on 11 Sep 2019

Yes, put it in your ~/.profile after sourcing the setup script, except I would write nixpkgs=$HOME/.nix-defexpr/channels/nixpkgs rather than nixpkgs-$NIX_PATH/nixpkgs in case NIX_PATH changes again to include something else.

Personally, I tweaked my profile to make sure NIX_PATH didn't have the string nixpkgs= in it first, before prepending the new path onto it.

lilyball on 11 Sep 2019

👍1

:/ This is still an issue with the recommended install method on Ubuntu.

$ curl https://nixos.org/nix/install | sh
$ . ~/.nix-profile/etc/profile.d/nix.sh
$ nix build nixpkgs.hello
error: attribute 'nixpkgs' in selection path 'nixpkgs.hello' not found

ElvishJerricco on 8 Oct 2019

Are there plans for a release incorporating this fix anytime soon?

t184256 on 16 Oct 2019

@t184256 Nix 2.3.1 was released the day after that commit, and includes the fix. It might not have been in nixpkgs when you posted, but it's definitely in the current nixpkgs-unstable.