[FEATURE] Support `cachix/install-nix-action`

[deemp]

Description of a problem the feature solves

Many people use the official cachix/install-nix-action and their workflows may depend on its features.

@C0D3-M4513R supposed that cache-nix-action may work with the install-nix-action (#48 (comment)).

Describe the solution you'd like

Support install-nix-action along with nix-quick-install-action.

Describe alternatives you've considered

Use nixbuild/nix-quick-install-action v30 or a more recent one.

Context

Differences between actions

Installation

• nix-quick-install-action uses single-user installation
• install-nix-action uses multi-user installation

TODO

(question to readers) Which missing features don't let you switch to nix-quick-install-action?

[chrisjenx]

We can't use nix-quick-install-action

[deemp]

@chrisjenx why?

[chrisjenx]

It doesn't support all the extra flags during setup, i.e:

          nix_path: nixpkgs=channel:nixos-unstable
          install_url: https://releases.nixos.org/nix/nix-2.19.7/install
          extra_nix_config: |
            max-substitution-jobs = 32
            accept-flake-config = true
            sandbox = false
            extra-substituters = ....
            extra-trusted-public-keys = ....

[deemp]

@chrisjenx which flags do you mean?

If you mean the values in the extra_nix_config in your example, you can just append them to nix.conf in the next step after installing Nix via nix-quick-install-action.

[deemp]

@C0D3-M4513R Which missing features don't let you switch to nix-quick-install-action?

[C0D3-M4513R]

I'm currently not aware of any, now that arm is supported.

Mainly it was the fact that it didn't support arm (yes, I saw your other comment), me just setting up docker builds using nix and then getting feedback on Matrix, that I should use the official installer.

[Mic92]

@C0D3-M4513R Which missing features don't let you switch to nix-quick-install-action?

The issue is that the namespaces created by the a single user nix installation are semantically not the same as a nix-daemon variant. I observed this by running the coreutils test suite.

[deemp]

@Mic92 which namespaces do you mean?

[Mic92]

Linux namespaces: https://man7.org/linux/man-pages/man7/namespaces.7.html

[Mic92]

Here is the list of tests we specifically disable for coreutils: https://github.com/NixOS/nixpkgs/blob/c8d36fe7be9ef579621f5f560eecdd09df2e0440/pkgs/tools/misc/coreutils/default.nix#L87

I expect more issues like this in other packages that no one fixes because hydra doesn't have this issue.

[Mic92]

Another thing I noticed is that this action doesn't seems to be updated regularly, it's still stuck on an old nix version, that is closed to be no longer receive security patches.