Nixpkgs: Warning: name collision in input Nix expressions, skipping

[mudrii]

Issue description

mudrii@nixos ~ $ nix-env -u ''
mudrii@nixos ~ $ nix-channel --update nixos
unpacking channels...
mudrii@nixos ~ $ nix-env -u ''
warning: name collision in input Nix expressions, skipping '/home/mudrii/.nix-defexpr/channels_root/nixos'

Steps to reproduce

From normal user run
nix-channel --update nixos
nix-env -u '*'

Technical details

Please run nix-shell -p nix-info --run "nix-info -m" and paste the
results.
mudrii@nixos ~ $ nix-shell -p nix-info --run "nix-info -m"

• system: "x86_64-linux"
• host os: Linux 4.19.13, NixOS, 19.03pre165037.eebd1a92637 (Koi)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.1.3
• channels(mudrii): "nixos-19.03pre165037.eebd1a92637"
• channels(root): "nixos-19.03pre165037.eebd1a92637"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

[mudrii]

The solution was provided by @danbst on discourse.nixos.org
Seems nixos channel was added for non-root user, and nix-env doesn’t know which nixos channel to use - root or non-root.

The fix is to remove the nixos channel from non-root user fixes the problem.

user@nixos ~ $ nix-channel --remove nixos

Note: I don't remember adding any nixos channel to non-root user.

[mudrii]

Is not exactly an issue but potential problem can be in not explicitly adding by normal user new channel why nix is showing an error.