func InitPidfile(job *engine.Job) engine.Status {
	if len(job.Args) == 0 {
		return job.Error(fmt.Errorf("no pidfile provided to initialize"))
	}
	job.Logf("Creating pidfile")
	if err := utils.CreatePidFile(job.Args[0]); err != nil {
		return job.Error(err)
	}
	return engine.StatusOK
}

func NewDaemonFromDirectory(config *Config, eng *engine.Engine) (*Daemon, error) {
	if config.Mtu == 0 {
		config.Mtu = getDefaultNetworkMtu()
	}
	// Check for mutually incompatible config options
	if config.BridgeIface != "" && config.BridgeIP != "" {
		return nil, fmt.Errorf("You specified -b & --bip, mutually exclusive options. Please specify only one.")
	}
	if !config.EnableIptables && !config.InterContainerCommunication {
		return nil, fmt.Errorf("You specified --iptables=false with --icc=false. ICC uses iptables to function. Please set --icc or --iptables to true.")
	}
	if !config.EnableIptables && config.EnableIpMasq {
		config.EnableIpMasq = false
	}
	config.DisableNetwork = config.BridgeIface == disableNetworkBridge

	// Claim the pidfile first, to avoid any and all unexpected race conditions.
	// Some of the init doesn't need a pidfile lock - but let's not try to be smart.
	if config.Pidfile != "" {
		if err := utils.CreatePidFile(config.Pidfile); err != nil {
			return nil, err
		}
		eng.OnShutdown(func() {
			// Always release the pidfile last, just in case
			utils.RemovePidFile(config.Pidfile)
		})
	}

	// Check that the system is supported and we have sufficient privileges
	if runtime.GOOS != "linux" {
		return nil, fmt.Errorf("The Docker daemon is only supported on linux")
	}
	if os.Geteuid() != 0 {
		return nil, fmt.Errorf("The Docker daemon needs to be run as root")
	}
	if err := checkKernelAndArch(); err != nil {
		return nil, err
	}

	// set up the TempDir to use a canonical path
	tmp, err := utils.TempDir(config.Root)
	if err != nil {
		return nil, fmt.Errorf("Unable to get the TempDir under %s: %s", config.Root, err)
	}
	realTmp, err := utils.ReadSymlinkedDirectory(tmp)
	if err != nil {
		return nil, fmt.Errorf("Unable to get the full path to the TempDir (%s): %s", tmp, err)
	}
	os.Setenv("TMPDIR", realTmp)
	if !config.EnableSelinuxSupport {
		selinuxSetDisabled()
	}

	// get the canonical path to the Docker root directory
	var realRoot string
	if _, err := os.Stat(config.Root); err != nil && os.IsNotExist(err) {
		realRoot = config.Root
	} else {
		realRoot, err = utils.ReadSymlinkedDirectory(config.Root)
		if err != nil {
			return nil, fmt.Errorf("Unable to get the full path to root (%s): %s", config.Root, err)
		}
	}
	config.Root = realRoot
	// Create the root directory if it doesn't exists
	if err := os.MkdirAll(config.Root, 0700); err != nil && !os.IsExist(err) {
		return nil, err
	}

	// Set the default driver
	graphdriver.DefaultDriver = config.GraphDriver

	// Load storage driver
	driver, err := graphdriver.New(config.Root, config.GraphOptions)
	if err != nil {
		return nil, err
	}
	log.Debugf("Using graph driver %s", driver)

	// As Docker on btrfs and SELinux are incompatible at present, error on both being enabled
	if selinuxEnabled() && config.EnableSelinuxSupport && driver.String() == "btrfs" {
		return nil, fmt.Errorf("SELinux is not supported with the BTRFS graph driver!")
	}

	daemonRepo := path.Join(config.Root, "containers")

	if err := os.MkdirAll(daemonRepo, 0700); err != nil && !os.IsExist(err) {
		return nil, err
	}

	// Migrate the container if it is aufs and aufs is enabled
	if err = migrateIfAufs(driver, config.Root); err != nil {
		return nil, err
	}

	log.Debugf("Creating images graph")
	g, err := graph.NewGraph(path.Join(config.Root, "graph"), driver)
	if err != nil {
		return nil, err
	}
//.........这里部分代码省略.........