@@ -1,8 +1,10 @@

 package docker

 import (

+	"bytes"

 	"errors"

 	"fmt"

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

 	"io"

 	"io/ioutil"

 	"os"

@@ -20,6 +22,37 @@ const (

 	Xz

 )

+func DetectCompression(source []byte) Compression {

+	for _, c := range source[:10] {

+		utils.Debugf("%x", c)

+	}

+

+	sourceLen := len(source)

+	for compression, m := range map[Compression][]byte{

+		Bzip2: {0x42, 0x5A, 0x68},

+		Gzip:  {0x1F, 0x8B, 0x08},

+		Xz:    {0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00},

+	} {

+		fail := false

+		if len(m) > sourceLen {

+			utils.Debugf("Len too short")

+			continue

+		}

+		i := 0

+		for _, b := range m {

+			if b != source[i] {

+				fail = true

+				break

+			}

+			i++

+		}

+		if !fail {

+			return compression

+		}

+	}

+	return Uncompressed

+}

+

 func (compression *Compression) Flag() string {

 	switch *compression {

 	case Bzip2:

@@ -47,12 +80,21 @@ func (compression *Compression) Extension() string {

 }

 func Tar(path string, compression Compression) (io.Reader, error) {

-	cmd := exec.Command("bsdtar", "-f", "-", "-C", path, "-c"+compression.Flag(), ".")

-	return CmdStream(cmd)

+	return CmdStream(exec.Command("tar", "-f", "-", "-C", path, "-c"+compression.Flag(), "."))

 }

 func Untar(archive io.Reader, path string) error {

-	cmd := exec.Command("bsdtar", "-f", "-", "-C", path, "-x")

+

+	buf := make([]byte, 10)

+	if _, err := archive.Read(buf); err != nil {

+		return err

+	}

+	compression := DetectCompression(buf)

+	archive = io.MultiReader(bytes.NewReader(buf), archive)

+

+	utils.Debugf("Archive compression detected: %s", compression.Extension())

+

+	cmd := exec.Command("tar", "-f", "-", "-C", path, "-x"+compression.Flag())

 	cmd.Stdin = archive

 	// Hardcode locale environment for predictable outcome regardless of host configuration.

 	//   (see https://github.com/dotcloud/docker/issues/355)