@@ -338,7 +338,7 @@ func populateCommand(c *Container, env []string) error {

 		Interface: nil,

 	}

-	parts := strings.SplitN(c.hostConfig.NetworkMode, ":", 2)

+	parts := strings.SplitN(string(c.hostConfig.NetworkMode), ":", 2)

 	switch parts[0] {

 	case "none":

 	case "host":

@@ -354,9 +354,9 @@ func populateCommand(c *Container, env []string) error {

 			}

 		}

 	case "container":

-		nc := c.daemon.Get(parts[1])

-		if nc == nil {

-			return fmt.Errorf("no such container to join network: %q", parts[1])

+		nc, err := c.getNetworkedContainer()

+		if err != nil {

+			return err

 		}

 		en.ContainerID = nc.ID

 	default:

@@ -536,7 +536,8 @@ ff02::2		ip6-allrouters

 }

 func (container *Container) allocateNetwork() error {

-	if container.Config.NetworkDisabled || container.hostConfig.NetworkMode == "host" {

+	mode := container.hostConfig.NetworkMode

+	if container.Config.NetworkDisabled || mode.IsContainer() || mode.IsHost() {

 		return nil

 	}

@@ -1045,7 +1046,7 @@ func (container *Container) setupContainerDns() error {

 func (container *Container) initializeNetworking() error {

 	var err error

-	if container.hostConfig.NetworkMode == "host" {

+	if container.hostConfig.NetworkMode.IsHost() {

 		container.Config.Hostname, err = os.Hostname()

 		if err != nil {

 			return err

@@ -1059,6 +1060,16 @@ func (container *Container) initializeNetworking() error {

 		container.HostsPath = "/etc/hosts"

 		container.buildHostname()

+	} else if container.hostConfig.NetworkMode.IsContainer() {

+		// we need to get the hosts files from the container to join

+		nc, err := container.getNetworkedContainer()

+		if err != nil {

+			return err

+		}

+		container.HostsPath = nc.HostsPath

+		container.ResolvConfPath = nc.ResolvConfPath

+		container.Config.Hostname = nc.Config.Hostname

+		container.Config.Domainname = nc.Config.Domainname

 	} else if container.daemon.config.DisableNetwork {

 		container.Config.NetworkDisabled = true

 		container.buildHostnameAndHostsFiles("127.0.1.1")

@@ -1268,3 +1279,20 @@ func (container *Container) GetMountLabel() string {

 	}

 	return container.MountLabel

 }

+

+func (container *Container) getNetworkedContainer() (*Container, error) {

+	parts := strings.SplitN(string(container.hostConfig.NetworkMode), ":", 2)

+	switch parts[0] {

+	case "container":

+		nc := container.daemon.Get(parts[1])

+		if nc == nil {

+			return nil, fmt.Errorf("no such container to join network: %s", parts[1])

+		}

+		if !nc.State.IsRunning() {

+			return nil, fmt.Errorf("cannot join network of a non running container: %s", parts[1])

+		}

+		return nc, nil

+	default:

+		return nil, fmt.Errorf("network mode not set to container")

+	}

+}

@@ -1,11 +1,24 @@

 package runconfig

 import (

+	"strings"

+

 	"github.com/dotcloud/docker/engine"

 	"github.com/dotcloud/docker/nat"

 	"github.com/dotcloud/docker/utils"

 )

+type NetworkMode string

+

+func (n NetworkMode) IsHost() bool {

+	return n == "host"

+}

+

+func (n NetworkMode) IsContainer() bool {

+	parts := strings.SplitN(string(n), ":", 2)

+	return len(parts) > 1 && parts[0] == "container"

+}

+

 type HostConfig struct {

 	Binds           []string

 	ContainerIDFile string

@@ -17,7 +30,7 @@ type HostConfig struct {

 	Dns             []string

 	DnsSearch       []string

 	VolumesFrom     []string

-	NetworkMode     string

+	NetworkMode     NetworkMode

 }

 func ContainerHostConfigFromJob(job *engine.Job) *HostConfig {

@@ -25,7 +38,7 @@ func ContainerHostConfigFromJob(job *engine.Job) *HostConfig {

 		ContainerIDFile: job.Getenv("ContainerIDFile"),

 		Privileged:      job.GetenvBool("Privileged"),

 		PublishAllPorts: job.GetenvBool("PublishAllPorts"),

-		NetworkMode:     job.Getenv("NetworkMode"),

+		NetworkMode:     NetworkMode(job.Getenv("NetworkMode")),

 	}

 	job.GetenvJson("LxcConf", &hostConfig.LxcConf)

 	job.GetenvJson("PortBindings", &hostConfig.PortBindings)

@@ -62,7 +62,7 @@ func parseRun(cmd *flag.FlagSet, args []string, sysInfo *sysinfo.SysInfo) (*Conf

 		flUser            = cmd.String([]string{"u", "-user"}, "", "Username or UID")

 		flWorkingDir      = cmd.String([]string{"w", "-workdir"}, "", "Working directory inside the container")

 		flCpuShares       = cmd.Int64([]string{"c", "-cpu-shares"}, 0, "CPU shares (relative weight)")

-		flNetMode         = cmd.String([]string{"-net"}, "bridge", "Set the Network mode for the container ('bridge': creates a new network stack for the container on the docker bridge, 'none': no networking for this container, 'container:name_or_id': reuses another container network stack)")

+		flNetMode         = cmd.String([]string{"-net"}, "bridge", "Set the Network mode for the container ('bridge': creates a new network stack for the container on the docker bridge, 'none': no networking for this container, 'container:<name|id>': reuses another container network stack)")

 		// For documentation purpose

 		_ = cmd.Bool([]string{"#sig-proxy", "-sig-proxy"}, true, "Proxify all received signal to the process (even in non-tty mode)")

 		_ = cmd.String([]string{"#name", "-name"}, "", "Assign a name to the container")

@@ -200,7 +200,7 @@ func parseRun(cmd *flag.FlagSet, args []string, sysInfo *sysinfo.SysInfo) (*Conf

 	netMode, err := parseNetMode(*flNetMode)

 	if err != nil {

-		return nil, nil, cmd, fmt.Errorf("-net: invalid net mode: %v", err)

+		return nil, nil, cmd, fmt.Errorf("--net: invalid net mode: %v", err)

 	}

 	config := &Config{

@@ -282,19 +282,16 @@ func parseKeyValueOpts(opts opts.ListOpts) ([]utils.KeyValuePair, error) {

 	return out, nil

 }

-func parseNetMode(netMode string) (string, error) {

+func parseNetMode(netMode string) (NetworkMode, error) {

 	parts := strings.Split(netMode, ":")

 	switch mode := parts[0]; mode {

-	case "bridge", "none":

-		return mode, nil

+	case "bridge", "none", "host":

 	case "container":

 		if len(parts) < 2 || parts[1] == "" {

-			return "", fmt.Errorf("'container:' netmode requires a container id or name", netMode)

+			return "", fmt.Errorf("invalid container format container:<name|id>")

 		}

-		return netMode, nil

-	case "host":

-		return netMode, nil

 	default:

-		return "", fmt.Errorf("invalid netmode: %q", netMode)

+		return "", fmt.Errorf("invalid --net: %s", netMode)

 	}

+	return NetworkMode(netMode), nil

 }