Intermittent `No such file or directory` error on `nh os switch`

[musjj]

Occasionally, after running nh os switch I get this error:

reloading user units for $USER...
restarting sysinit-reactivation.target
the following new units were started: NetworkManager-dispatcher.service, sysinit-reactivation.target, systemd-ask-password-console.path, systemd-tmpfiles-resetup.service
The application panicked (crashed).
Message:  called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }
Location: src/nixos.rs:269

Please report the bug at https://github.com/nix-community/nh/issues

Re-running nh os switch right after it usually fixes it, but I can't reproduce it consistently.

[zzzsyyy]

Edited: remove system.switch.enable = false; fixed my issue

Seems to be the same issue, log is

Closure size: 2847 -> 2834 (2667 paths added, 2680 paths removed, delta -13, disk usage -13.7MiB).
The application panicked (crashed).
Message:  called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }
Location: src/nixos.rs:254

Please report the bug at https://github.com/nix-community/nh/issues

[NotAShelf]

This... is to be execpted since nh invokes switch-to-configuration internally, but I had hoped that it was handled better (having never looked specifically at switching.) I'll add a check to bail out early with a more specific message when switch-to-configuration is missing.

[NotAShelf]

With e5dbcf9 the failure is handled more gracefully. I don't intend to add a workaround, but the error message now describe what the actual issue is.

[musjj]

I've never disabled system.switch in my config:

nix-repl> config.system.switch
{
  enable = true;
  enableNg = true;
}

Can this be re-opened?

[NotAShelf]

The error message indicates, for some reason, that switch-to-configuration is missing in current system. This is only the case (as per my knowledge) when and only when switch is disabled. I don't think there is not much we could do on Nh's side than simply erroring out when the switch command is missing. The path is one and true, it doesn't change haphazardly.

For the sake of debugging though, could you verify that /nix/var/nix/profiles/system/bin/switch-to-configuration exists?

[NotAShelf]

Actually, could you also please send the output with --verbose?

[musjj]

for some reason, that switch-to-configuration is missing in current system.

I suspect that there's a race condition somewhere, because immediately re-running nh os switch for the second time usually fixes the issue.

could you also please send the output with --verbose?

I'll try to run nh os switch with --verbose more often from now on, but the issue is intermittent and can't be consistently reproduced (at least, I can't find a way to).

could you verify that /nix/var/nix/profiles/system/bin/switch-to-configuration exists?

It exists now, but I'll try to check it next time immediately after the error occurs.