@@ -9,12 +9,20 @@ import (

 	"path"

 )

+func init() {

+	graphdriver.Register("aufs", Init)

+}

+

 type AufsDriver struct {

 }

 // New returns a new AUFS driver.

 // An error is returned if AUFS is not supported.

-func New() (*AufsDriver, error) {

+func Init(root string) (graphdriver.Driver, error) {

+	// Try to load the aufs kernel module

+	if err := exec.Command("modprobe", "aufs").Run(); err != nil {

+		return nil, err

+	}

 	return &AufsDriver{}, nil

 }

@@ -2,11 +2,16 @@ package devmapper

 import (

 	"fmt"

+	"github.com/dotcloud/docker/archive"

+	"github.com/dotcloud/docker/graphdriver"

 	"os"

 	"path"

-	"github.com/dotcloud/docker/archive"

 )

+func init() {

+	graphdriver.Register("devicemapper", Init)

+}

+

 // Placeholder interfaces, to be replaced

 // at integration.

@@ -17,22 +22,19 @@ type Image interface {

 }

 type Change interface {

-

 }

 // End of placeholder interfaces.

-

-

 type Driver struct {

 	*DeviceSet

 	home string

 }

-func Init(home string) (*Driver, error) {

+func Init(home string) (graphdriver.Driver, error) {

 	d := &Driver{

 		DeviceSet: NewDeviceSet(home),

-		home: home,

+		home:      home,

 	}

 	if err := d.DeviceSet.ensureInit(); err != nil {

 		return nil, err

@@ -64,7 +66,7 @@ func (d *Driver) OnCreate(img Image, layer archive.Archive) error {

 	if err := d.DeviceSet.MountDevice(img.ID(), mp, false); err != nil {

 		return err

 	}

-	// Apply the layer as a diff 

+	// Apply the layer as a diff

 	if layer != nil {

 		if err := archive.ApplyLayer(mp, layer); err != nil {

 			return err

@@ -3,6 +3,8 @@ package docker

 import (

 	"fmt"

 	"github.com/dotcloud/docker/archive"

+	_ "github.com/dotcloud/docker/aufs"

+	_ "github.com/dotcloud/docker/devmapper"

 	"github.com/dotcloud/docker/graphdriver"

 	"github.com/dotcloud/docker/utils"

 	"io"

@@ -18,12 +20,12 @@ import (

 type Graph struct {

 	Root    string

 	idIndex *utils.TruncIndex

-	driver graphdriver.Driver

+	driver  graphdriver.Driver

 }

 // NewGraph instantiates a new graph at the given root path in the filesystem.

 // `root` will be created if it doesn't exist.

-func NewGraph(root string, driver graphdriver.Driver) (*Graph, error) {

+func NewGraph(root string) (*Graph, error) {

 	abspath, err := filepath.Abs(root)

 	if err != nil {

 		return nil, err

@@ -32,10 +34,16 @@ func NewGraph(root string, driver graphdriver.Driver) (*Graph, error) {

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

 		return nil, err

 	}

+

+	driver, err := graphdriver.New(root)

+	if err != nil {

+		return nil, err

+	}

+

 	graph := &Graph{

 		Root:    abspath,

 		idIndex: utils.NewTruncIndex(),

-		driver: driver,

+		driver:  driver,

 	}

 	if err := graph.restore(); err != nil {

 		return nil, err

@@ -242,7 +250,7 @@ func (graph *Graph) getDockerInitLayer() (string, error) {

 func (graph *Graph) tmp() (*Graph, error) {

 	// Changed to _tmp from :tmp:, because it messed with ":" separators in aufs branch syntax...

-	return NewGraph(path.Join(graph.Root, "_tmp"), graph.driver)

+	return NewGraph(path.Join(graph.Root, "_tmp"))

 }

 // Check if given error is "not empty".

@@ -1,5 +1,55 @@

 package graphdriver

+import (

+	"fmt"

+)

+

+type InitFunc func(root string) (Driver, error)

+

+var (

+	// All registred drivers

+	drivers map[string]InitFunc

+	// Slice of drivers that should be used in an order

+	priority = []string{

+		"aufs",

+		"devicemapper",

+	}

+)

+

+func Register(name string, initFunc InitFunc) error {

+	if _, exists := drivers[name]; exists {

+		return fmt.Errorf("Name already registered %s", name)

+	}

+	drivers[name] = initFunc

+

+	return nil

+}

+

+func New(root string) (Driver, error) {

+	var driver Driver

+	var lastError error

+	// Check for priority drivers first

+	for _, name := range priority {

+		if initFunc, exists := drivers[name]; exists {

+			driver, lastError = initFunc(root)

+			if lastError != nil {

+				continue

+			}

+			return driver, nil

+		}

+	}

+

+	// Check all registered drivers if no priority driver is found

+	for _, initFunc := range drivers {

+		driver, lastError = initFunc(root)

+		if lastError != nil {

+			continue

+		}

+		return driver, nil

+	}

+	return nil, lastError

+}

+

 type Image interface {

 	Layers() ([]string, error)

 }

@@ -5,7 +5,6 @@ import (

 	"container/list"

 	"database/sql"

 	"fmt"

-	"github.com/dotcloud/docker/aufs"

 	"github.com/dotcloud/docker/gograph"

 	"github.com/dotcloud/docker/utils"

 	"io"

@@ -574,16 +573,12 @@ func NewRuntimeFromDirectory(config *DaemonConfig) (*Runtime, error) {

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

 		return nil, err

 	}

-	driver, err := aufs.New()

-	if err != nil {

-		return nil, err

-	}

-	g, err := NewGraph(path.Join(config.Root, "graph"), driver)

+	g, err := NewGraph(path.Join(config.Root, "graph"))

 	if err != nil {

 		return nil, err

 	}

-	volumes, err := NewGraph(path.Join(config.Root, "volumes"), driver)

+	volumes, err := NewGraph(path.Join(config.Root, "volumes"))

 	if err != nil {

 		return nil, err

 	}