Java not found on NixOS

[pishleback]

Trying to install FAF on NixOS.

I've followed all the installation steps up to running ./run, which outputs:

No suitable Java Virtual Machine could be found on your system.
The version of the JVM must be at least 21.
Please define INSTALL4J_JAVA_HOME to point to a suitable JVM.

The steam part of my configuration.nix looks like

  programs.steam = {
    enable = true;

    remotePlay.openFirewall = true;
    dedicatedServer.openFirewall = true;

    package = with pkgs; steam.override {
      extraPkgs = pkgs: [
        jq
        cabextract
        wget
        git
        pkgsi686Linux.libpulseaudio
        pkgsi686Linux.freetype
        pkgsi686Linux.xorg.libXcursor
        pkgsi686Linux.xorg.libXcomposite
        pkgsi686Linux.xorg.libXi
      ];
    };
  };

When running setup.sh I can see java.tar.gz being downloaded and extracted, and there is a jdk-21.0.5+11 folder inside the faf-linux folder. I've also tried installing java system-wide (verified with java -version) but java is still not found by ./run.

I've tried running ./update-component.sh java "<java url>" with the latest <java url> as in the main readme, but that does not fix it.

Running all commands inside steam-run bash.

Any ideas? Thanks

[pishleback]

I've managed to fudge it by adding a line to manually set app_java_home inside faf-linux/faf-client-2025.9.2/faf-client to point at faf-linux/jdk-21.0.5+11. Where is app_java_home supposed to be set? It'd be nice to get to the bottom of why it's not being set.

[iczero]

INSTALL4J_JAVA_HOME is set here: https://github.com/FAForever/faf-linux/blob/master/run#L14

I am not sure why that isn't working, can you please do a quick check regarding that?

[pishleback]

So INSTALL4J_JAVA_HOME does get set correctly in run to point at jdk-21.0.5+11, confirmed with an echo after the export. But app_java_home in faf-linux/faf-client-2025.9.2/faf-client does not get set for whatever reason. I'm not great with bash scripts so it's hard for me to say why not.