nixos-config/machine/oracle-installer/kexec.nix

{ pkgs, config, ... }:

{
  system.build = rec {
    image = pkgs.runCommand "image" { buildInputs = [ pkgs.nukeReferences ]; } ''
      mkdir $out
      cp ${config.system.build.kernel}/${config.system.boot.loader.kernelFile} $out/kernel
      cp ${config.system.build.netbootRamdisk}/initrd $out/initrd
      echo "init=${builtins.unsafeDiscardStringContext config.system.build.toplevel}/init ${toString config.boot.kernelParams}" > $out/cmdline
      nuke-refs $out/kernel
    '';
    kexec_script = pkgs.writeTextFile {
      executable = true;
      name = "kexec-nixos";
      text = ''
        #!${pkgs.stdenv.shell}
        export PATH=${pkgs.kexectools}/bin:${pkgs.cpio}/bin:$PATH
        set -x
        set -e
        cd $(mktemp -d)
        pwd
        mkdir initrd
        pushd initrd
        if [ -e /ssh_pubkey ]; then
          cat /ssh_pubkey >> authorized_keys
        fi
        find -type f | cpio -o -H newc | gzip -9 > ../extra.gz
        popd
        cat ${image}/initrd extra.gz > final.gz

        kexec -l ${image}/kernel --initrd=final.gz --append="init=${builtins.unsafeDiscardStringContext config.system.build.toplevel}/init ${toString config.boot.kernelParams}"
        sync
        echo "executing kernel, filesystems will be improperly umounted"
        kexec -e
      '';
    };
  };
  boot.initrd.postMountCommands = ''
    mkdir -p /mnt-root/root/.ssh/
    cp /authorized_keys /mnt-root/root/.ssh/
  '';
  system.build.kexec_tarball = pkgs.callPackage (pkgs.path + "/nixos/lib/make-system-tarball.nix") {
    storeContents = [
      {
        object = config.system.build.kexec_script;
        symlink = "/kexec_nixos";
      }
    ];
    contents = [ ];
  };
}