@@ -424,7 +424,7 @@ func (container *Container) buildHostsFiles(IP string) error {

 	}

 	container.HostsPath = hostsPath

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

+	var extraContent []etchosts.Record

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

 	if err != nil {

@@ -433,15 +433,15 @@ func (container *Container) buildHostsFiles(IP string) error {

 	for linkAlias, child := range children {

 		_, alias := path.Split(linkAlias)

-		extraContent[alias] = child.NetworkSettings.IPAddress

+		extraContent = append(extraContent, etchosts.Record{Hosts: alias, IP: child.NetworkSettings.IPAddress})

 	}

 	for _, extraHost := range container.hostConfig.ExtraHosts {

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

-		extraContent[parts[0]] = parts[1]

+		extraContent = append(extraContent, etchosts.Record{Hosts: parts[0], IP: parts[1]})

 	}

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

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

 }

 func (container *Container) buildHostnameAndHostsFiles(IP string) error {

@@ -3,40 +3,54 @@ package etchosts

 import (

 	"bytes"

 	"fmt"

+	"io"

 	"io/ioutil"

 	"regexp"

 )

-var defaultContent = map[string]string{

-	"localhost":                            "127.0.0.1",

-	"localhost ip6-localhost ip6-loopback": "::1",

-	"ip6-localnet":                         "fe00::0",

-	"ip6-mcastprefix":                      "ff00::0",

-	"ip6-allnodes":                         "ff02::1",

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

+type Record struct {

+	Hosts string

+	IP    string

 }

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

+func (r Record) WriteTo(w io.Writer) (int64, error) {

+	n, err := fmt.Fprintf(w, "%s\t%s\n", r.IP, r.Hosts)

+	return int64(n), err

+}

+

+var defaultContent = []Record{

+	{Hosts: "localhost", IP: "127.0.0.1"},

+	{Hosts: "localhost ip6-localhost ip6-loopback", IP: "::1"},

+	{Hosts: "ip6-localnet", IP: "fe00::0"},

+	{Hosts: "ip6-mcastprefix", IP: "ff00::0"},

+	{Hosts: "ip6-allnodes", IP: "ff02::1"},

+	{Hosts: "ip6-allrouters", IP: "ff02::2"},

+}

+

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

 	content := bytes.NewBuffer(nil)

 	if IP != "" {

+		var mainRec Record

+		mainRec.IP = IP

 		if domainname != "" {

-			content.WriteString(fmt.Sprintf("%s\t%s.%s %s\n", IP, hostname, domainname, hostname))

+			mainRec.Hosts = fmt.Sprintf("%s.%s %s", hostname, domainname, hostname)

 		} else {

-			content.WriteString(fmt.Sprintf("%s\t%s\n", IP, hostname))

+			mainRec.Hosts = hostname

+		}

+		if _, err := mainRec.WriteTo(content); err != nil {

+			return err

 		}

 	}

-	for hosts, ip := range defaultContent {

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

+	for _, r := range defaultContent {

+		if _, err := r.WriteTo(content); err != nil {

 			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

-			}

+	for _, r := range extraContent {

+		if _, err := r.WriteTo(content); err != nil {

+			return err

 		}

 	}

@@ -7,6 +7,32 @@ import (

 	"testing"

 )

+func TestBuildDefault(t *testing.T) {

+	file, err := ioutil.TempFile("", "")

+	if err != nil {

+		t.Fatal(err)

+	}

+	defer os.Remove(file.Name())

+

+	// check that /etc/hosts has consistent ordering

+	for i := 0; i <= 5; i++ {

+		err = Build(file.Name(), "", "", "", nil)

+		if err != nil {

+			t.Fatal(err)

+		}

+

+		content, err := ioutil.ReadFile(file.Name())

+		if err != nil {

+			t.Fatal(err)

+		}

+		expected := "127.0.0.1\tlocalhost\n::1\tlocalhost ip6-localhost ip6-loopback\nfe00::0\tip6-localnet\nff00::0\tip6-mcastprefix\nff02::1\tip6-allnodes\nff02::2\tip6-allrouters\n"

+

+		if expected != string(content) {

+			t.Fatalf("Expected to find '%s' got '%s'", expected, content)

+		}

+	}

+}

+

 func TestBuildHostnameDomainname(t *testing.T) {

 	file, err := ioutil.TempFile("", "")

 	if err != nil {