@@ -357,7 +357,20 @@ func (container *Container) buildHostnameAndHostsFiles(IP string) error {

 	}

 	container.HostsPath = path.Join(container.root, "hosts")

-	return etchosts.Build(container.HostsPath, IP, container.Config.Hostname, container.Config.Domainname)

+

+	extraContent := make(map[string]string)

+

+	children, err := container.daemon.Children(container.Name)

+	if err != nil {

+		return err

+	}

+

+	for linkAlias, child := range children {

+		_, alias := path.Split(linkAlias)

+		extraContent[alias] = child.NetworkSettings.IPAddress

+	}

+

+	return etchosts.Build(container.HostsPath, IP, container.Config.Hostname, container.Config.Domainname, &extraContent)

 }

 func (container *Container) allocateNetwork() error {

@@ -1,4 +1,4 @@

-page_title: Docker Run Reference 

+page_title: Docker Run Reference

 page_description: Configure containers at runtime

 page_keywords: docker, run, configure, runtime

@@ -407,6 +407,13 @@ And we can use that information to connect from another container as a client:

     $ docker run -i -t --rm --link redis-name:redis_alias --entrypoint /bin/bash dockerfiles/redis -c '/redis-stable/src/redis-cli -h $REDIS_ALIAS_PORT_6379_TCP_ADDR -p $REDIS_ALIAS_PORT_6379_TCP_PORT'

     172.17.0.32:6379>

+Docker will also map the private IP address to the alias of a linked

+container by inserting an entry into `/etc/hosts`.  You can use this

+mechanism to communicate with a linked container by its alias:

+

+    $ docker run -d --name servicename busybox sleep 30

+    $ docker run -i -t --link servicename:servicealias busybox ping -c 1 servicealias

+

 ## VOLUME (Shared Filesystems)

     -v=[]: Create a bind mount with: [host-dir]:[container-dir]:[rw|ro].

@@ -109,3 +109,32 @@ the Redis container.

     CONTAINER ID        IMAGE                        COMMAND                CREATED              STATUS              PORTS               NAMES

     4c01db0b339c        ubuntu:12.04                 bash                   17 seconds ago       Up 16 seconds                           webapp

     d7886598dbe2        crosbymichael/redis:latest   /redis-server --dir    33 minutes ago       Up 33 minutes       6379/tcp            redis,webapp/db

+

+## Resolving Links by Name

+

+New in version v0.11.

+

+Linked containers can be accessed by hostname.  Hostnames are mapped by

+appending entries to '/etc/hosts' using the linked container's alias.

+

+For example, linking a container using '--link redis:db' will generate the

+following '/etc/hosts' file:

+

+    root@6541a75d44a0:/# cat /etc/hosts

+    172.17.0.3  6541a75d44a0

+    172.17.0.2  db

+

+    127.0.0.1   localhost

+    ::1     localhost ip6-localhost ip6-loopback

+    fe00::0     ip6-localnet

+    ff00::0     ip6-mcastprefix

+    ff02::1     ip6-allnodes

+    ff02::2     ip6-allrouters

+    root@6541a75d44a0:/#

+

+Using this mechanism, you can communicate with the linked container by

+name:

+

+    root@6541a75d44a0:/# echo PING | redis-cli -h db

+    PONG

+    root@6541a75d44a0:/#

new file mode 100644

@@ -0,0 +1,45 @@

+package main

+

+import (

+	"fmt"

+	"os/exec"

+	"testing"

+)

+

+func TestPingUnlinkedContainers(t *testing.T) {

+	runCmd := exec.Command(dockerBinary, "run", "--rm", "busybox", "sh", "-c", "ping -c 1 alias1 -W 1 && ping -c 1 alias2 -W 1")

+	exitCode, err := runCommand(runCmd)

+

+	if exitCode == 0 {

+		t.Fatal("run ping did not fail")

+	} else if exitCode != 1 {

+		errorOut(err, t, fmt.Sprintf("run ping failed with errors: %v", err))

+	}

+}

+

+func TestPingLinkedContainers(t *testing.T) {

+	cmd := exec.Command(dockerBinary, "run", "-d", "--name", "container1", "busybox", "sleep", "10")

+	out, _, err := runCommandWithOutput(cmd)

+	errorOut(err, t, fmt.Sprintf("run container1 failed with errors: %v", err))

+	idA := stripTrailingCharacters(out)

+

+	cmd = exec.Command(dockerBinary, "run", "-d", "--name", "container2", "busybox", "sleep", "10")

+	out, _, err = runCommandWithOutput(cmd)

+	errorOut(err, t, fmt.Sprintf("run container2 failed with errors: %v", err))

+	idB := stripTrailingCharacters(out)

+

+	cmd = exec.Command(dockerBinary, "run", "--rm", "--link", "container1:alias1", "--link", "container2:alias2", "busybox", "sh", "-c", "ping -c 1 alias1 -W 1 && ping -c 1 alias2 -W 1")

+	out, _, err = runCommandWithOutput(cmd)

+	fmt.Printf("OUT: %s", out)

+	errorOut(err, t, fmt.Sprintf("run ping failed with errors: %v", err))

+

+	cmd = exec.Command(dockerBinary, "kill", idA)

+	_, err = runCommand(cmd)

+	errorOut(err, t, fmt.Sprintf("failed to kill container1: %v", err))

+

+	cmd = exec.Command(dockerBinary, "kill", idB)

+	_, err = runCommand(cmd)

+	errorOut(err, t, fmt.Sprintf("failed to kill container2: %v", err))

+

+	deleteAllContainers()

+}

@@ -15,7 +15,7 @@ var defaultContent = map[string]string{

 	"ip6-allrouters":                       "ff02::2",

 }

-func Build(path, IP, hostname, domainname string) error {

+func Build(path, IP, hostname, domainname string, extraContent *map[string]string) error {

 	content := bytes.NewBuffer(nil)

 	if IP != "" {

 		if domainname != "" {

@@ -30,5 +30,14 @@ func Build(path, IP, hostname, domainname string) error {

 			return err

 		}

 	}

+

+	if extraContent != nil {

+		for hosts, ip := range *extraContent {

+			if _, err := content.WriteString(fmt.Sprintf("%s\t%s\n", ip, hosts)); err != nil {

+				return err

+			}

+		}

+	}

+

 	return ioutil.WriteFile(path, content.Bytes(), 0644)

 }