diff --git a/lib/WatchDog.js b/lib/WatchDog.js
index 0c8f154c..81e283ad 100644
--- a/lib/WatchDog.js
+++ b/lib/WatchDog.js
@@ -23,7 +23,7 @@ function generateId() {
   var crypto = require('crypto');
   var os     = require('os');
 
-  var parts = [os.hostname(), process.pid, +(new Date)];
+  var parts = [os.hostname(), JSON.stringify(os.networkInterfaces)];
   var hash = crypto.createHash('md5').update(parts.join(''));
   return hash.digest('hex');
 }
diff --git a/scripts/install.js b/scripts/install.js
index 9790a844..ee194751 100644
--- a/scripts/install.js
+++ b/scripts/install.js
@@ -4,6 +4,10 @@ var WatchDog = require('../lib/WatchDog.js');
 var fs       = require('fs');
 var cst      = require('../constants.js');
 
+if (fs.existsSync(cst.WATCHDOG_FILE)) {
+  process.exit(0);
+}
+
 (function pre_init() {
   fs.exists(cst.DEFAULT_FILE_PATH, function(exist) {
     if (!exist) {