@@ -150,6 +150,7 @@ func (s *TagStore) CmdLookup(job *engine.Job) engine.Status {

 		out.Set("Os", image.OS)

 		out.SetInt64("Size", image.Size)

 		out.SetInt64("VirtualSize", image.GetParentsSize(0)+image.Size)

+		out.Set("Checksum", image.Checksum)

 		if _, err = out.WriteTo(job.Stdout); err != nil {

 			return job.Error(err)

 		}

@@ -11,6 +11,7 @@ import (

 	log "github.com/Sirupsen/logrus"

 	"github.com/docker/docker/pkg/archive"

+	"github.com/docker/docker/pkg/tarsum"

 	"github.com/docker/docker/runconfig"

 	"github.com/docker/docker/utils"

 )

@@ -32,6 +33,7 @@ type Image struct {

 	Config          *runconfig.Config `json:"config,omitempty"`

 	Architecture    string            `json:"architecture,omitempty"`

 	OS              string            `json:"os,omitempty"`

+	Checksum        string            `json:"checksum"`

 	Size            int64

 	graph Graph

@@ -77,19 +79,43 @@ func LoadImage(root string) (*Image, error) {

 	return img, nil

 }

+// StoreImage stores file system layer data for the given image to the

+// image's registered storage driver. Image metadata is stored in a file

+// at the specified root directory. This function also computes the TarSum

+// of `layerData` (currently using tarsum.dev).

 func StoreImage(img *Image, layerData archive.ArchiveReader, root string) error {

 	// Store the layer

 	var (

-		size   int64

-		err    error

-		driver = img.graph.Driver()

+		size        int64

+		err         error

+		driver      = img.graph.Driver()

+		layerTarSum tarsum.TarSum

 	)

 	// If layerData is not nil, unpack it into the new layer

 	if layerData != nil {

-		if size, err = driver.ApplyDiff(img.ID, img.Parent, layerData); err != nil {

+		layerDataDecompressed, err := archive.DecompressStream(layerData)

+		if err != nil {

 			return err

 		}

+

+		defer layerDataDecompressed.Close()

+

+		if layerTarSum, err = tarsum.NewTarSum(layerDataDecompressed, true, tarsum.VersionDev); err != nil {

+			return err

+		}

+

+		if size, err = driver.ApplyDiff(img.ID, img.Parent, layerTarSum); err != nil {

+			return err

+		}

+

+		checksum := layerTarSum.Sum(nil)

+

+		if img.Checksum != "" && img.Checksum != checksum {

+			log.Warn("image layer checksum mismatch: computed %q, expected %q", checksum, img.Checksum)

+		}

+

+		img.Checksum = checksum

 	}

 	img.Size = size