Make nsinit a proper go pkg and add the main in another dir

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

libcontainer/README.md

@@ -72,9 +72,11 @@ rootfs and copy a `container.json` file into the directory with your specified c
 
 To execution `/bin/bash` in the current directory as a container just run:
 ```bash
-nsinit exec /bin/bash
+nsinit -tty exec /bin/bash
 ```
 
+If you want a proper tty setup inside the new container you must use the `-tty` flag when running nsinit.
+
 If you wish to spawn another process inside the container while your current bash session is 
 running just run the exact same command again to get another bash shell or change the command.  If the original process dies, PID 1, all other processes spawned inside the container will also be killed and the namespace will be removed. 
 

libcontainer/nsinit/exec.go

@@ -1,6 +1,6 @@
 // +build linux
 
-package main
+package nsinit
 
 import (
 	"fmt"
@@ -16,7 +16,9 @@ import (
 	"syscall"
 )
 
-func execCommand(container *libcontainer.Container, tty bool, args []string) (int, error) {
+// Exec performes setup outside of a namespace so that a container can be
+// executed.  Exec is a high level function for working with container namespaces.
+func Exec(container *libcontainer.Container, tty bool, args []string) (int, error) {
 	var (
 		master  *os.File
 		console string

libcontainer/nsinit/execin.go

@@ -1,4 +1,4 @@
-package main
+package nsinit
 
 import (
 	"fmt"
@@ -11,7 +11,8 @@ import (
 	"syscall"
 )
 
-func execinCommand(container *libcontainer.Container, nspid int, args []string) (int, error) {
+// ExecIn uses an existing pid and joins the pid's namespaces with the new command.
+func ExecIn(container *libcontainer.Container, nspid int, args []string) (int, error) {
 	for _, ns := range container.Namespaces {
 		if err := system.Unshare(namespaceMap[ns]); err != nil {
 			return -1, err

libcontainer/nsinit/init.go

@@ -1,6 +1,6 @@
 // +build linux
 
-package main
+package nsinit
 
 import (
 	"fmt"
@@ -15,7 +15,9 @@ import (
 	"syscall"
 )
 
-func initCommand(container *libcontainer.Container, console string, pipe io.ReadCloser, args []string) error {
+// Init is the init process that first runs inside a new namespace to setup mounts, users, networking,
+// and other options required for the new container.
+func Init(container *libcontainer.Container, console string, pipe io.ReadCloser, args []string) error {
 	rootfs, err := resolveRootfs()
 	if err != nil {
 		return err

libcontainer/nsinit/mount.go

@@ -1,6 +1,6 @@
 // +build linux
 
-package main
+package nsinit
 
 import (
 	"fmt"

libcontainer/nsinit/ns_linux.go

@@ -1,4 +1,4 @@
-package main
+package nsinit
 
 import (
 	"github.com/dotcloud/docker/pkg/libcontainer"

libcontainer/nsinit/nsinit/main.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"flag"
 	"github.com/dotcloud/docker/pkg/libcontainer"
+	"github.com/dotcloud/docker/pkg/libcontainer/nsinit"
 	"io/ioutil"
 	"log"
 	"os"
@@ -42,9 +43,9 @@ func main() {
 			}
 		}
 		if nspid > 0 {
-			exitCode, err = execinCommand(container, nspid, flag.Args()[1:])
+			exitCode, err = nsinit.ExecIn(container, nspid, flag.Args()[1:])
 		} else {
-			exitCode, err = execCommand(container, *tty, flag.Args()[1:])
+			exitCode, err = nsinit.Exec(container, *tty, flag.Args()[1:])
 		}
 		if err != nil {
 			log.Fatal(err)
@@ -54,7 +55,7 @@ func main() {
 		if flag.NArg() < 2 {
 			log.Fatal(ErrWrongArguments)
 		}
-		if err := initCommand(container, *console, os.NewFile(uintptr(*pipeFd), "pipe"), flag.Args()[1:]); err != nil {
+		if err := nsinit.Init(container, *console, os.NewFile(uintptr(*pipeFd), "pipe"), flag.Args()[1:]); err != nil {
 			log.Fatal(err)
 		}
 	default: