nix upgrade-nix does not detect 2.4

[Dzieni]

Describe the bug

My collegaue has problems with remote builds using Nix 2.4. To see if it's a matter of different Nix version (I use 2.3 myself), I wanted to upgrade. However, I'm not sure how to do this.

Steps To Reproduce

1. Run nix-channel --update, then nix upgrade-nix.

Expected behavior

According to --help, it should upgrade Nix to the latest stable version. Latest stable version is 2.4, but I get this output instead:

[0.0 MiB DL]
replacing old 'nix-2.3.16'
installing 'nix-2.3.16'
upgrade to version 2.3.16 done

nix-env --version output

2.3.16, as mentioned above.

Additional context

I also tried to upgrade using nix-env -u and it managed to upgrade to nix-2.4pre-rc1. Then, after running nix upgrade-nix, it downgraded to 2.3:

replacing old 'nix-2.4pre-rc1'
installing 'nix-2.3.16'

OS: macOS Big Sur 11.3.1

[Dzieni]

Is it possibly related to the fact that I run my Nix single-user and it's no longer supported in v2.4?

https://github.com/NixOS/nix/blob/2.4-maintenance/scripts/install-nix-from-closure.sh#L63

If so, I think it should be mentioned in release notes...?

[abathur]

Is it possibly related to the fact that I run my Nix single-user and it's no longer supported in v2.4?

No. Upgrade pulls the latest version from a file in nixpkgs (which still indicates 2.3.16).

I am not sure exactly what the criteria for updating it is, but I assume this is waiting for nixpkgs itself to complete updating (see NixOS/nixpkgs#144197).

[Dzieni]

@abathur does it mean that the best workaround for now is to just reinstall Nix from scratch?

[abathur]

I would personally treat that as a last resort, if you need exactly the same version. (uninstall/reinstall experience has sharp corners and can be frustrating). Nixpkgs also includes a nixUnstable attr (also known as nixFlakes) which should be a pre-2.5 build that isn't too far ahead of 2.4 at this point.

I haven't tried using this via nix-env, but if the wiki page for flakes is right, something like nix-env -iA nixpkgs.nixUnstable should work.

[abathur]

The nixpkgs PR I mentioned before has been merged--this should work now.

[matu3ba]

I can confirm that this works now:

[user@pc zsh]$ nix --version
nix (Nix) 2.4pre20210429_d15a196
[user@pc zsh]$ nix upgrade
error: 'upgrade' is not a recognised command
Try 'nix --help' for more information.
[user@pc zsh]$ nix --help
[user@pc zsh]$ nix-channel --update
unpacking channels...
[user@pc zsh]$ nix upgrade-nix
replacing old 'nix-2.4pre20210429_d15a196'
installing 'nix-2.11.0'
building '/nix/store/lyrzv64mi81lj04fh0qjg6vx5xbqmm6i-user-environment.drv'...
[user@pc zsh]$ nix --version
nix (Nix) 2.11.0
[user@pc zsh]$