Update for nsenter

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)

nsinit/exec.go

@@ -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()))

nsinit/init.go

@@ -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)

nsinit/main.go

@@ -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 {

nsinit/nsenter.go

@@ -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)
+	}
+}

nsinit/spec.go

@@ -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
 }

nsinit/stats.go

@@ -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
 }

nsinit/utils.go

@@ -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
+}