Do not attempt to install kvm on self-hosted runners

[dpc]

I have a CI that have some things working on self-hosted runners, and some on normal Github runners.

Currently, after switching:

-      - uses: cachix/install-nix-action@v30
+      - uses: DeterminateSystems/nix-installer-action@v16

The CI fails on self-hosted runners, because it tries to install KVM, but there is no sudo.

It seems to me that if the Nix was already installed, the machine is probably a self-hosted one, and there's no point trying to install KVM.

I will probably end up disabling KVM, but ideally I would be happy to have it enabled on non-self-hosted machines.

Edit:

Seems like currently the existing Nix installation is not even correctly detected.

self-hosted runners just have nix in the PATH, and do not actually require installing anything. The action is still useful if it needs to run on a Github Actions standard runner in a VM.

[dpc]

Ehh... I forgot this doesn't work. Bummer. I really would love to switch.

[grahamc]

Hmm... interesting. So, installing Nix requires sudo. @dpc does your machine already have Nix? I have a fix for the KVM + sudo issue, but obviously it won't help if you don't have Nix installed.

[dpc]

Hmm... interesting. So, installing Nix requires sudo. @dpc does your machine already have Nix? I have a fix for the KVM + sudo issue, but obviously it won't help if you don't have Nix installed.

Yes. It's a self-hosted runner. A hetzner box with NixOS installed and github runners configured.

It does require some working around actions sometimes, because some github actions assume that they are running on a fresh VM Ubuntu, etc. but most github actions don't touch any system-level stuff, so it just works for them.

I wouldn't really need nix-installer-action in the first place there BUT the same workflows are used when using MacOS builders, and possibly in the VM when people fork our repo. So it would be really nice if DeterminateSystems/nix-installer-action could just detect that Nix is installed and sudo doesn't work and just assumed it's OK instead of failing, so I we can have the best Nix installer when it is needed.

[dpc]

I have submitted a PR that works in our CI.