Failed to generate image: Could not find the 'nwdiag', 'nwdiag3' executable in PATH; add it to the PATH or specify its location using the 'nwdiag' document attribute
nwdiag {
  network dmz {
      address = "210.x.x.x/24"

      web01 [address = "210.x.x.1"];
      web02 [address = "210.x.x.2"];
  }
  network internal {
      address = "172.x.x.x/24";

      web01 [address = "172.x.x.1"];
      web02 [address = "172.x.x.2"];
      db01;
      db02;
  }
}

Failed to generate image: Could not find the 'blockdiag', 'blockdiag3' executable in PATH; add it to the PATH or specify its location using the 'blockdiag' document attribute
blockdiag {
   A -> B -> C -> D;
   A -> E -> F -> G;
}

Failed to generate image: Could not find the 'rackdiag', 'rackdiag3' executable in PATH; add it to the PATH or specify its location using the 'rackdiag' document attribute
rackdiag {
  // define 1st rack
  rack {
    16U;

    // define rack items
    1: UPS [2U];
    3: DB Server
    4: Web Server
    5: Web Server
    6: Web Server
    7: Load Balancer
    8: L3 Switch
  }

  // define 2nd rack
  rack {
    12U;

    // define rack items
    1: UPS [2U];
    3: DB Server
    4: Web Server
    5: Web Server
    6: Web Server
    7: Load Balancer
    8: L3 Switch
  }
}