@@ -95,18 +95,27 @@ func supportsAufs() error {

 	return fmt.Errorf("AUFS was not found in /proc/filesystems")

 }

-func (a *AufsDriver) rootPath() string {

+func (a AufsDriver) rootPath() string {

 	return a.root

 }

-func (a *AufsDriver) String() string {

+func (AufsDriver) String() string {

 	return "aufs"

 }

-func (d *AufsDriver) Status() [][2]string {

+func (AufsDriver) Status() [][2]string {

 	return nil

 }

+// Exists returns true if the given id is registered with

+// this driver

+func (a AufsDriver) Exists(id string) bool {

+	if _, err := os.Lstat(path.Join(a.rootPath(), "layers", id)); err != nil {

+		return false

+	}

+	return true

+}

+

 // Three folders are created for each id

 // mnt, layers, and diff

 func (a *AufsDriver) Create(id, parent string) error {

new file mode 100644

@@ -0,0 +1,183 @@

+package aufs

+

+import (

+	"encoding/json"

+	"fmt"

+	"io/ioutil"

+	"os"

+	"path"

+)

+

+type metadata struct {

+	ID       string `json:"id"`

+	ParentID string `json:"parent,omitempty"`

+	Image    string `json:"Image,omitempty"`

+

+	parent *metadata

+}

+

+func pathExists(pth string) bool {

+	if _, err := os.Stat(pth); err != nil {

+		return false

+	}

+	return true

+}

+

+// Migrate existing images and containers from docker < 0.7.x

+//

+// The format pre 0.7 is for docker to store the metadata and filesystem

+// content in the same directory.  For the migration to work we need to move Image layer

+// data from /var/lib/docker/graph/<id>/layers to the diff of the registered id.

+//

+// Next we need to migrate the container's rw layer to diff of the driver.  After the

+// contents are migrated we need to register the image and container ids with the

+// driver.

+//

+// For the migration we try to move the folder containing the layer files, if that

+// fails because the data is currently mounted we will fallback to creating a

+// symlink.

+func (a *AufsDriver) Migrate(pth string, setupInit func(p string) error) error {

+	if pathExists(path.Join(pth, "graph")) {

+		if err := a.migrateImages(path.Join(pth, "graph")); err != nil {

+			return err

+		}

+		return a.migrateContainers(path.Join(pth, "containers"), setupInit)

+	}

+	return nil

+}

+

+func (a *AufsDriver) migrateContainers(pth string, setupInit func(p string) error) error {

+	fis, err := ioutil.ReadDir(pth)

+	if err != nil {

+		return err

+	}

+

+	for _, fi := range fis {

+		if id := fi.Name(); fi.IsDir() && pathExists(path.Join(pth, id, "rw")) {

+			if err := tryRelocate(path.Join(pth, id, "rw"), path.Join(a.rootPath(), "diff", id)); err != nil {

+				return err

+			}

+

+			if !a.Exists(id) {

+

+				metadata, err := loadMetadata(path.Join(pth, id, "config.json"))

+				if err != nil {

+					return err

+				}

+

+				initID := fmt.Sprintf("%s-init", id)

+				if err := a.Create(initID, metadata.Image); err != nil {

+					return err

+				}

+

+				initPath, err := a.Get(initID)

+				if err != nil {

+					return err

+				}

+				// setup init layer

+				if err := setupInit(initPath); err != nil {

+					return err

+				}

+

+				if err := a.Create(id, initID); err != nil {

+					return err

+				}

+			}

+		}

+	}

+	return nil

+}

+

+func (a *AufsDriver) migrateImages(pth string) error {

+	fis, err := ioutil.ReadDir(pth)

+	if err != nil {

+		return err

+	}

+	var (

+		m       = make(map[string]*metadata)

+		current *metadata

+		exists  bool

+	)

+

+	for _, fi := range fis {

+		if id := fi.Name(); fi.IsDir() && pathExists(path.Join(pth, id, "layer")) {

+			if current, exists = m[id]; !exists {

+				current, err = loadMetadata(path.Join(pth, id, "json"))

+				if err != nil {

+					return err

+				}

+				m[id] = current

+			}

+		}

+	}

+

+	for _, v := range m {

+		v.parent = m[v.ParentID]

+	}

+

+	migrated := make(map[string]bool)

+	for _, v := range m {

+		if err := a.migrateImage(v, pth, migrated); err != nil {

+			return err

+		}

+	}

+	return nil

+}

+

+func (a *AufsDriver) migrateImage(m *metadata, pth string, migrated map[string]bool) error {

+	if !migrated[m.ID] {

+		if m.parent != nil {

+			a.migrateImage(m.parent, pth, migrated)

+		}

+		if err := tryRelocate(path.Join(pth, m.ID, "layer"), path.Join(a.rootPath(), "diff", m.ID)); err != nil {

+			return err

+		}

+		if !a.Exists(m.ID) {

+			if err := a.Create(m.ID, m.ParentID); err != nil {

+				return err

+			}

+		}

+		migrated[m.ID] = true

+	}

+	return nil

+}

+

+// tryRelocate will try to rename the old path to the new pack and if

+// the operation fails, it will fallback to a symlink

+func tryRelocate(oldPath, newPath string) error {

+	s, err := os.Lstat(newPath)

+	if err != nil && !os.IsNotExist(err) {

+		return err

+	}

+	// If the destination is a symlink then we already tried to relocate once before

+	// and it failed so we delete it and try to remove

+	if s != nil && s.Mode()&os.ModeSymlink == os.ModeSymlink {

+		if err := os.RemoveAll(newPath); err != nil {

+			return err

+		}

+	}

+	if err := os.Rename(oldPath, newPath); err != nil {

+		if sErr := os.Symlink(oldPath, newPath); sErr != nil {

+			return fmt.Errorf("Unable to relocate %s to %s: Rename err %s Symlink err %s", oldPath, newPath, err, sErr)

+		}

+	}

+	return nil

+}

+

+func loadMetadata(pth string) (*metadata, error) {

+	f, err := os.Open(pth)

+	if err != nil {

+		return nil, err

+	}

+	defer f.Close()

+

+	var (

+		out = &metadata{}

+		dec = json.NewDecoder(f)

+	)

+

+	if err := dec.Decode(out); err != nil {

+		return nil, err

+	}

+	return out, nil

+}

@@ -8,7 +8,7 @@ import (

 	"github.com/dotcloud/docker/archive"

 	"github.com/dotcloud/docker/graphdb"

 	"github.com/dotcloud/docker/graphdriver"

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

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

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

 	_ "github.com/dotcloud/docker/graphdriver/dummy"

 	"github.com/dotcloud/docker/utils"

@@ -629,6 +629,12 @@ func NewRuntimeFromDirectory(config *DaemonConfig) (*Runtime, error) {

 		return nil, err

 	}

+	if ad, ok := driver.(*aufs.AufsDriver); ok {

+		if err := ad.Migrate(config.Root, setupInitLayer); err != nil {

+			return nil, err

+		}

+	}

+

 	if err := linkLxcStart(config.Root); err != nil {

 		return nil, err

 	}