Daemonize (fork()) and install metrics_daemon in the image for execution.

src/platform/metrics_daemon/metrics_daemon.cc

 // Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "platform/metrics_daemon/metrics_daemon.h"
 
 #include <glib-object.h>
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/file.h>
 #include <sys/stat.h>
+#include <unistd.h>
 
 extern "C" {
 #include "marshal_void__string_boxed.h"
 }
 
 #include <base/logging.h>
 
 #define SAFE_MESSAGE(e) ((e && e->message) ? e->message : "unknown error")
 #define READ_WRITE_ALL_FILE_FLAGS \
   (S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH)
 
 const char* MetricsDaemon::kMetricsFilePath = "/tmp/.chromeos-metrics";
 
 MetricsDaemon::NetworkState
 MetricsDaemon::network_states_[MetricsDaemon::kNumberNetworkStates] = {
 #define STATE(name, capname) { #name, "Connman" # capname },
 #include "network_states.h"
 };
 
-void MetricsDaemon::Run(bool testing) {
+void MetricsDaemon::Run(bool run_as_daemon, bool testing) {
   Init(testing);
-  Loop();
+  if (!run_as_daemon || daemon(0, 0) == 0) {
+    Loop();
+  }
 }
 
 void MetricsDaemon::Init(bool testing) {
   testing_ = testing;
   network_state_id_ = kUnknownNetworkStateId;
 
   // Opens the file to communicate with Chrome, and keep it open.
   metrics_fd_ = open(kMetricsFilePath, O_WRONLY | O_APPEND | O_CREAT,
                      READ_WRITE_ALL_FILE_FLAGS);
   PLOG_IF(FATAL, metrics_fd_ < 0) << kMetricsFilePath;
@@ skipping 147 matching lines @@
 
   if (flock(metrics_fd_, LOCK_UN) < 0) {
     // error("unlock", path, errno);
     return;
   }
 }
 
 void MetricsDaemon::TestPublishMetric(const char* name, const char* value) {
   LOG(INFO) << "received metric: " << name << " " << value;
 }