Add config command to nsinit

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

nsinit/config.go

@@ -0,0 +1,106 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"os"
+	"path/filepath"
+	"syscall"
+
+	"github.com/codegangsta/cli"
+	"github.com/docker/libcontainer/configs"
+)
+
+var configCommand = cli.Command{
+	Name:  "config",
+	Usage: "generate a standard configuration file for a container",
+	Flags: []cli.Flag{
+		cli.StringFlag{Name: "file,f", Value: "stdout", Usage: "write the configuration to the specified file"},
+	},
+	Action: func(context *cli.Context) {
+		template := getTemplate()
+		data, err := json.MarshalIndent(template, "", "\t")
+		if err != nil {
+			fatal(err)
+		}
+		var f *os.File
+		filePath := context.String("file")
+		switch filePath {
+		case "stdout", "":
+			f = os.Stdout
+		default:
+			if f, err = os.Create(filePath); err != nil {
+				fatal(err)
+			}
+			defer f.Close()
+		}
+		if _, err := io.Copy(f, bytes.NewBuffer(data)); err != nil {
+			fatal(err)
+		}
+	},
+}
+
+func getTemplate() *configs.Config {
+	cwd, err := os.Getwd()
+	if err != nil {
+		panic(err)
+	}
+	return &configs.Config{
+		Rootfs:            cwd,
+		ParentDeathSignal: int(syscall.SIGKILL),
+		Capabilities: []string{
+			"CHOWN",
+			"DAC_OVERRIDE",
+			"FSETID",
+			"FOWNER",
+			"MKNOD",
+			"NET_RAW",
+			"SETGID",
+			"SETUID",
+			"SETFCAP",
+			"SETPCAP",
+			"NET_BIND_SERVICE",
+			"SYS_CHROOT",
+			"KILL",
+			"AUDIT_WRITE",
+		},
+		Namespaces: configs.Namespaces([]configs.Namespace{
+			{Type: configs.NEWNS},
+			{Type: configs.NEWUTS},
+			{Type: configs.NEWIPC},
+			{Type: configs.NEWPID},
+			{Type: configs.NEWNET},
+		}),
+		Cgroups: &configs.Cgroup{
+			Name:            filepath.Base(cwd),
+			Parent:          "nsinit",
+			AllowAllDevices: false,
+			AllowedDevices:  configs.DefaultAllowedDevices,
+		},
+
+		Devices:  configs.DefaultAutoCreatedDevices,
+		Hostname: "nsinit",
+		Networks: []*configs.Network{
+			{
+				Type:    "loopback",
+				Address: "127.0.0.1/0",
+				Gateway: "localhost",
+			},
+		},
+		Rlimits: []configs.Rlimit{
+			{
+				Type: syscall.RLIMIT_NOFILE,
+				Hard: uint64(1024),
+				Soft: uint64(1024),
+			},
+		},
+		Mounts: []*configs.Mount{
+			{
+				Type:        "tmpfs",
+				Destination: "/tmp",
+			},
+		},
+	}
+
+}

nsinit/main.go

@@ -24,6 +24,7 @@ func main() {
 		pauseCommand,
 		statsCommand,
 		unpauseCommand,
+		configCommand,
 	}
 	if err := app.Run(os.Args); err != nil {
 		log.Fatal(err)