func NewDaemonFromDirectory(config *daemonconfig.Config, eng *engine.Engine) (*Daemon, error) {
	if runtime.GOOS != "linux" {
		log.Fatalf("The Docker daemon is only supported on linux")
	}
	if os.Geteuid() != 0 {
		log.Fatalf("The Docker daemon needs to be run as root")
	}
	if err := checkKernelAndArch(); err != nil {
		log.Fatal(err)
	}

	// set up the TempDir to use a canonical path
	tmp, err := utils.TempDir(config.Root)
	if err != nil {
		log.Fatalf("Unable to get the TempDir under %s: %s", config.Root, err)
	}
	realTmp, err := utils.ReadSymlinkedDirectory(tmp)
	if err != nil {
		log.Fatalf("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 {
			log.Fatalf("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
	}
	utils.Debugf("Using graph driver %s", driver)

	// As Docker on btrfs and SELinux are incompatible at present, error on both being enabled
	if 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
	}

	utils.Debugf("Creating images graph")
	g, err := graph.NewGraph(path.Join(config.Root, "graph"), driver)
	if err != nil {
		return nil, err
	}

	// We don't want to use a complex driver like aufs or devmapper
	// for volumes, just a plain filesystem
	volumesDriver, err := graphdriver.GetDriver("vfs", config.Root, config.GraphOptions)
	if err != nil {
		return nil, err
	}
	utils.Debugf("Creating volumes graph")
	volumes, err := graph.NewGraph(path.Join(config.Root, "volumes"), volumesDriver)
	if err != nil {
		return nil, err
	}
	utils.Debugf("Creating repository list")
	repositories, err := graph.NewTagStore(path.Join(config.Root, "repositories-"+driver.String()), g)
	if err != nil {
		return nil, fmt.Errorf("Couldn't create Tag store: %s", err)
	}

	if !config.DisableNetwork {
		job := eng.Job("init_networkdriver")

		job.SetenvBool("EnableIptables", config.EnableIptables)
		job.SetenvBool("InterContainerCommunication", config.InterContainerCommunication)
		job.SetenvBool("EnableIpForward", config.EnableIpForward)
		job.Setenv("BridgeIface", config.BridgeIface)
		job.Setenv("BridgeIP", config.BridgeIP)
		job.Setenv("DefaultBindingIP", config.DefaultIp.String())

//.........这里部分代码省略.........

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.........

func main() {
	if len(dockerConfDir) == 0 {
		dockerConfDir = filepath.Join(os.Getenv("HOME"), ".docker")
	}
	if selfPath := utils.SelfPath(); strings.Contains(selfPath, ".dockerinit") {
		// Running in init mode
		sysinit.SysInit()
		return
	}

	var (
		flVersion            = flag.Bool([]string{"v", "-version"}, false, "Print version information and quit")
		flDaemon             = flag.Bool([]string{"d", "-daemon"}, false, "Enable daemon mode")
		flGraphOpts          opts.ListOpts
		flDebug              = flag.Bool([]string{"D", "-debug"}, false, "Enable debug mode")
		flAutoRestart        = flag.Bool([]string{"r", "-restart"}, true, "Restart previously running containers")
		bridgeName           = flag.String([]string{"b", "-bridge"}, "", "Attach containers to a pre-existing network bridge\nuse 'none' to disable container networking")
		bridgeIp             = flag.String([]string{"#bip", "-bip"}, "", "Use this CIDR notation address for the network bridge's IP, not compatible with -b")
		pidfile              = flag.String([]string{"p", "-pidfile"}, "/var/run/docker.pid", "Path to use for daemon PID file")
		flRoot               = flag.String([]string{"g", "-graph"}, "/var/lib/docker", "Path to use as the root of the Docker runtime")
		flSocketGroup        = flag.String([]string{"G", "-group"}, "docker", "Group to assign the unix socket specified by -H when running in daemon mode\nuse '' (the empty string) to disable setting of a group")
		flEnableCors         = flag.Bool([]string{"#api-enable-cors", "-api-enable-cors"}, false, "Enable CORS headers in the remote API")
		flDns                = opts.NewListOpts(opts.ValidateIPAddress)
		flDnsSearch          = opts.NewListOpts(opts.ValidateDnsSearch)
		flEnableIptables     = flag.Bool([]string{"#iptables", "-iptables"}, true, "Enable Docker's addition of iptables rules")
		flEnableIpForward    = flag.Bool([]string{"#ip-forward", "-ip-forward"}, true, "Enable net.ipv4.ip_forward")
		flDefaultIp          = flag.String([]string{"#ip", "-ip"}, "0.0.0.0", "Default IP address to use when binding container ports")
		flInterContainerComm = flag.Bool([]string{"#icc", "-icc"}, true, "Enable inter-container communication")
		flGraphDriver        = flag.String([]string{"s", "-storage-driver"}, "", "Force the Docker runtime to use a specific storage driver")
		flExecDriver         = flag.String([]string{"e", "-exec-driver"}, "native", "Force the Docker runtime to use a specific exec driver")
		flHosts              = opts.NewListOpts(api.ValidateHost)
		flMtu                = flag.Int([]string{"#mtu", "-mtu"}, 0, "Set the containers network MTU\nif no value is provided: default to the default route MTU or 1500 if no default route is available")
		flTls                = flag.Bool([]string{"-tls"}, false, "Use TLS; implied by tls-verify flags")
		flTlsVerify          = flag.Bool([]string{"-tlsverify"}, false, "Use TLS and verify the remote (daemon: verify client, client: verify daemon)")
		flCa                 = flag.String([]string{"-tlscacert"}, filepath.Join(dockerConfDir, defaultCaFile), "Trust only remotes providing a certificate signed by the CA given here")
		flCert               = flag.String([]string{"-tlscert"}, filepath.Join(dockerConfDir, defaultCertFile), "Path to TLS certificate file")
		flKey                = flag.String([]string{"-tlskey"}, filepath.Join(dockerConfDir, defaultKeyFile), "Path to TLS key file")
		flSelinuxEnabled     = flag.Bool([]string{"-selinux-enabled"}, false, "Enable selinux support. SELinux does not presently support the BTRFS storage driver")
	)
	flag.Var(&flDns, []string{"#dns", "-dns"}, "Force Docker to use specific DNS servers")
	flag.Var(&flDnsSearch, []string{"-dns-search"}, "Force Docker to use specific DNS search domains")
	flag.Var(&flHosts, []string{"H", "-host"}, "The socket(s) to bind to in daemon mode\nspecified using one or more tcp://host:port, unix:///path/to/socket, fd://* or fd://socketfd.")
	flag.Var(&flGraphOpts, []string{"-storage-opt"}, "Set storage driver options")

	flag.Parse()

	if *flVersion {
		showVersion()
		return
	}
	if flHosts.Len() == 0 {
		defaultHost := os.Getenv("DOCKER_HOST")

		if defaultHost == "" || *flDaemon {
			// If we do not have a host, default to unix socket
			defaultHost = fmt.Sprintf("unix://%s", api.DEFAULTUNIXSOCKET)
		}
		if _, err := api.ValidateHost(defaultHost); err != nil {
			log.Fatal(err)
		}
		flHosts.Set(defaultHost)
	}

	if *bridgeName != "" && *bridgeIp != "" {
		log.Fatal("You specified -b & --bip, mutually exclusive options. Please specify only one.")
	}

	if !*flEnableIptables && !*flInterContainerComm {
		log.Fatal("You specified --iptables=false with --icc=false. ICC uses iptables to function. Please set --icc or --iptables to true.")
	}

	if net.ParseIP(*flDefaultIp) == nil {
		log.Fatalf("Specified --ip=%s is not in correct format \"0.0.0.0\".", *flDefaultIp)
	}

	if *flDebug {
		os.Setenv("DEBUG", "1")
	}

	if *flDaemon {
		if runtime.GOOS != "linux" {
			log.Fatalf("The Docker daemon is only supported on linux")
		}
		if os.Geteuid() != 0 {
			log.Fatalf("The Docker daemon needs to be run as root")
		}

		if flag.NArg() != 0 {
			flag.Usage()
			return
		}

		// set up the TempDir to use a canonical path
		tmp := os.TempDir()
		realTmp, err := utils.ReadSymlinkedDirectory(tmp)
		if err != nil {
			log.Fatalf("Unable to get the full path to the TempDir (%s): %s", tmp, err)
		}
		os.Setenv("TMPDIR", realTmp)

//.........这里部分代码省略.........