@@ -19,17 +19,19 @@ var execCommand = cli.Command{

 }

 func execAction(context *cli.Context) {

-	var (

-		err             error

-		nspid, exitCode int

-	)

+	var nspid, exitCode int

+

+	container, err := loadContainer()

+	if err != nil {

+		log.Fatal(err)

+	}

 	if nspid, err = readPid(); err != nil && !os.IsNotExist(err) {

 		log.Fatalf("unable to read pid: %s", err)

 	}

 	if nspid > 0 {

-		exitCode, err = namespaces.ExecIn(container, nspid, []string(context.Args()))

+		err = namespaces.ExecIn(container, nspid, []string(context.Args()))

 	} else {

 		term := namespaces.NewTerminal(os.Stdin, os.Stdout, os.Stderr, container.Tty)

 		exitCode, err = startContainer(container, term, dataPath, []string(context.Args()))

@@ -22,6 +22,11 @@ var (

 )

 func initAction(context *cli.Context) {

+	container, err := loadContainer()

+	if err != nil {

+		log.Fatal(err)

+	}

+

 	rootfs, err := os.Getwd()

 	if err != nil {

 		log.Fatal(err)

@@ -5,21 +5,15 @@ import (

 	"os"

 	"github.com/codegangsta/cli"

-	"github.com/dotcloud/docker/pkg/libcontainer"

 )

-var (

-	container *libcontainer.Container

-	logPath   = os.Getenv("log")

-)

-

-func preload(context *cli.Context) (err error) {

-	container, err = loadContainer()

-	if err != nil {

-		return err

-	}

+var logPath = os.Getenv("log")

+func preload(context *cli.Context) error {

 	if logPath != "" {

+		if err := openLog(logPath); err != nil {

+			return err

+		}

 	}

 	return nil

@@ -37,6 +31,7 @@ func main() {

 		initCommand,

 		statsCommand,

 		specCommand,

+		nsenterCommand,

 	}

 	if err := app.Run(os.Args); err != nil {

new file mode 100644

@@ -0,0 +1,40 @@

+package main

+

+import (

+	"log"

+	"strconv"

+

+	"github.com/codegangsta/cli"

+	"github.com/dotcloud/docker/pkg/libcontainer/namespaces"

+)

+

+var nsenterCommand = cli.Command{

+	Name:   "nsenter",

+	Usage:  "init process for entering an existing namespace",

+	Action: nsenterAction,

+}

+

+func nsenterAction(context *cli.Context) {

+	args := context.Args()

+	if len(args) < 4 {

+		log.Fatalf("incorrect usage: <pid> <process label> <container JSON> <cmd>...")

+	}

+

+	container, err := loadContainerFromJson(args.Get(2))

+	if err != nil {

+		log.Fatalf("unable to load container: %s", err)

+	}

+

+	nspid, err := strconv.Atoi(args.Get(0))

+	if err != nil {

+		log.Fatalf("unable to read pid: %s from %q", err, args.Get(0))

+	}

+

+	if nspid <= 0 {

+		log.Fatalf("cannot enter into namespaces without valid pid: %q", nspid)

+	}

+

+	if err := namespaces.NsEnter(container, args.Get(1), nspid, args[3:]); err != nil {

+		log.Fatalf("failed to nsenter: %s", err)

+	}

+}

@@ -4,7 +4,6 @@ import (

 	"encoding/json"

 	"fmt"

 	"log"

-	"os"

 	"github.com/codegangsta/cli"

 	"github.com/dotcloud/docker/pkg/libcontainer"

@@ -17,15 +16,17 @@ var specCommand = cli.Command{

 }

 func specAction(context *cli.Context) {

-	// returns the spec of the current container.

+	container, err := loadContainer()

+	if err != nil {

+		log.Fatal(err)

+	}

+

 	spec, err := getContainerSpec(container)

 	if err != nil {

-		log.Printf("Failed to get spec - %v\n", err)

-		os.Exit(1)

+		log.Fatalf("Failed to get spec - %v\n", err)

 	}

-	fmt.Printf("Spec:\n%v\n", spec)

-	os.Exit(0)

+	fmt.Printf("Spec:\n%v\n", spec)

 }

 // returns the container spec in json format.

@@ -34,5 +35,6 @@ func getContainerSpec(container *libcontainer.Container) (string, error) {

 	if err != nil {

 		return "", err

 	}

+

 	return string(spec), nil

 }

@@ -4,7 +4,6 @@ import (

 	"encoding/json"

 	"fmt"

 	"log"

-	"os"

 	"github.com/codegangsta/cli"

 	"github.com/dotcloud/docker/pkg/libcontainer"

@@ -18,14 +17,17 @@ var statsCommand = cli.Command{

 }

 func statsAction(context *cli.Context) {

-	// returns the stats of the current container.

+	container, err := loadContainer()

+	if err != nil {

+		log.Fatal(err)

+	}

+

 	stats, err := getContainerStats(container)

 	if err != nil {

-		log.Printf("Failed to get stats - %v\n", err)

-		os.Exit(1)

+		log.Fatalf("Failed to get stats - %v\n", err)

 	}

+

 	fmt.Printf("Stats:\n%v\n", stats)

-	os.Exit(0)

 }

 // returns the container stats in json format.

@@ -34,9 +36,11 @@ func getContainerStats(container *libcontainer.Container) (string, error) {

 	if err != nil {

 		return "", err

 	}

+

 	out, err := json.MarshalIndent(stats, "", "\t")

 	if err != nil {

 		return "", err

 	}

+

 	return string(out), nil

 }

@@ -50,3 +50,13 @@ func openLog(name string) error {

 	return nil

 }

+

+func loadContainerFromJson(rawData string) (*libcontainer.Container, error) {

+	var container *libcontainer.Container

+

+	if err := json.Unmarshal([]byte(rawData), &container); err != nil {

+		return nil, err

+	}

+

+	return container, nil

+}