error "unsharing filesystem state in download"

[Valodim]

Cheers Nix folks :)

Describe the bug

Our CI threw the following error today:

0.232 unexpected error in download thread: error: unsharing filesystem state in download thread: Operation not permitted
0.232 error: download of 'https://github.com/nixos/nixpkgs/archive/1f91fd1040667e9265a760b0347f8bc416249da7.tar.gz' was interrupted

Steps To Reproduce

We are using the nix docker image, The dockerfile starts as follows:

FROM nixos/nix

WORKDIR /var/build

ADD shell.nix .
RUN nix-shell --command true

Error happens in the RUN command. The shell.nix content is (simplified):

let
  pkgs = import (builtins.fetchTarball {
    name = "nixos-21.05-2021-06-15";
    url = "https://github.com/nixos/nixpkgs/archive/1f91fd1040667e9265a760b0347f8bc416249da7.tar.gz";
    sha256 = "sha256-krXZQ0lObduC95f40K3JwIT//VIBpXBwVNclqh5njtE=";
  }) { };
in
  pkgs.mkShell {
    buildInputs = with pkgs; [
      # some packages
    ];
  }

As you can see from the dockerfile, we use the latest tag for the image. This error came up today, and indeed 11 hours ago a tag was pushed that updated nix from 2.3.13 to 2.5.0. Pinning the image tag to 2.3.12 fixes the error, so this seems to be an issue with 2.5.0.

As always, thanks for your work on Nix 👍

[vcunat]

The next ticket is also about this: #5777

[Valodim]

Ah, you're right! I thought I had searched for "unsharing" before filing this bug, but evidently I didn't (or hit the wrong issue tracker). The reproduction mentioned there is also simpler.

Closing this issue as a duplicate.

[Omrigan]

Can we maybe have 2.4 in the meantime for those who need flakes support?

[vcunat]

You can use the 2.3 to install 2.4, and... I'm just kidding. (I don't have access for this hub repo.)