@@ -347,3 +347,20 @@ func UdevWait(cookie uint32) error {

 func LogInitVerbose(level int) {

 	C.dm_log_init_verbose(C.int(level))

 }

+

+// Useful helper for cleanup

+func RemoveDevice(name string) error {

+	task := TaskCreate(DeviceRemove)

+	if task == nil {

+		return fmt.Errorf("Can't create task of type DeviceRemove")

+	}

+	err := task.SetName(name)

+	if err != nil {

+		return fmt.Errorf("Can't set task name %s", name)

+	}

+	err = task.Run()

+	if err != nil {

+		return fmt.Errorf("Error running removeDevice")

+	}

+	return nil

+}

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

 	"github.com/dotcloud/docker/utils"

 	"github.com/dotcloud/docker/devmapper"

 	"io"

+	"io/ioutil"

 	"log"

 	"net"

 	"os"

@@ -84,6 +85,32 @@ func layerArchive(tarfile string) (io.Reader, error) {

 	return f, nil

 }

+// Remove any leftover device mapper devices from earlier runs of the unit tests

+func cleanupDevMapper() {

+	infos, _ := ioutil.ReadDir("/dev/mapper")

+	if infos != nil {

+		hasPool := false

+		for _, info := range infos {

+			name := info.Name()

+			if strings.HasPrefix(name, "docker-unit-tests-devices-") {

+				if name == "docker-unit-tests-devices-pool" {

+					hasPool = true

+				} else {

+					if err := devmapper.RemoveDevice(name); err != nil {

+						panic(fmt.Errorf("Unable to remove existing device %s: %s", name, err))

+					}

+				}

+			}

+			// We need to remove the pool last as the other devices block it

+			if hasPool {

+				if err := devmapper.RemoveDevice("docker-unit-tests-devices-pool"); err != nil {

+					panic(fmt.Errorf("Unable to remove existing device docker-unit-tests-devices-pool: %s", name, err))

+				}

+			}

+		}

+	}

+}

+

 func init() {

 	os.Setenv("TEST", "1")

@@ -99,6 +126,8 @@ func init() {

 	NetworkBridgeIface = unitTestNetworkBridge

+	cleanupDevMapper()

+

 	// Always start from a clean set of loopback mounts

 	err := os.RemoveAll(unitTestStoreDevicesBase)

 	if err != nil {