OSX compilation

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume.charmes@dotcloud.com> (github: creack)
Upstream-commit: f3c48ec584707a9acaf9d79c2e161dadf1d2c99b
Component: engine

components/engine/pkg/libcontainer/nsinit/exec.go

@@ -1,3 +1,5 @@
+// +build linux
+
 package main
 
 import (

components/engine/pkg/libcontainer/nsinit/init.go

@@ -1,3 +1,5 @@
+// +build linux
+
 package main
 
 import (

components/engine/pkg/libcontainer/nsinit/main.go

@@ -2,17 +2,27 @@ package main
 
 import (
 	"encoding/json"
+	"errors"
 	"github.com/dotcloud/docker/pkg/libcontainer"
 	"log"
 	"os"
 )
 
+var (
+	ErrUnsupported    = errors.New("Unsupported method")
+	ErrWrongArguments = errors.New("Wrong argument count")
+)
+
 func main() {
 	container, err := loadContainer()
 	if err != nil {
 		log.Fatal(err)
 	}
 
+	argc := len(os.Args)
+	if argc < 2 {
+		log.Fatal(ErrWrongArguments)
+	}
 	switch os.Args[1] {
 	case "exec":
 		exitCode, err := execCommand(container)
@@ -21,6 +31,9 @@ func main() {
 		}
 		os.Exit(exitCode)
 	case "init":
+		if argc != 3 {
+			log.Fatal(ErrWrongArguments)
+		}
 		if err := initCommand(container, os.Args[2]); err != nil {
 			log.Fatal(err)
 		}

components/engine/pkg/libcontainer/nsinit/mount.go

@@ -1,3 +1,5 @@
+// +build linux
+
 package main
 
 import (