Merge pull request #205 from tonistiigi/exec

Add exec command

exec.go

@@ -0,0 +1,72 @@
+// +build linux
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"github.com/Sirupsen/logrus"
+	"github.com/codegangsta/cli"
+	"github.com/opencontainers/specs"
+)
+
+var execCommand = cli.Command{
+	Name:  "exec",
+	Usage: "execute new process inside the container",
+	Action: func(context *cli.Context) {
+		config, err := loadProcessConfig(context.Args().First())
+		if err != nil {
+			fatal(err)
+		}
+		if os.Geteuid() != 0 {
+			logrus.Fatal("runc should be run as root")
+		}
+		status, err := execProcess(context, config)
+		if err != nil {
+			logrus.Fatalf("exec failed: %v", err)
+		}
+		os.Exit(status)
+	},
+}
+
+func execProcess(context *cli.Context, config *specs.Process) (int, error) {
+	container, err := getContainer(context)
+	if err != nil {
+		return -1, err
+	}
+	process := newProcess(*config)
+
+	rootuid, err := container.Config().HostUID()
+	if err != nil {
+		return -1, err
+	}
+	tty, err := newTty(config.Terminal, process, rootuid)
+	if err != nil {
+		return -1, err
+	}
+	handler := newSignalHandler(tty)
+	defer handler.Close()
+	if err := container.Start(process); err != nil {
+		return -1, err
+	}
+	return handler.forward(process)
+}
+
+// loadProcessConfig loads the process configuration from the provided path.
+func loadProcessConfig(path string) (*specs.Process, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, fmt.Errorf("JSON configuration file for %s not found", path)
+		}
+		return nil, err
+	}
+	defer f.Close()
+	var s *specs.Process
+	if err := json.NewDecoder(f).Decode(&s); err != nil {
+		return nil, err
+	}
+	return s, nil
+}

main.go

@@ -63,6 +63,7 @@ func main() {
 		specCommand,
 		pauseCommand,
 		resumeCommand,
+		execCommand,
 	}
 	app.Before = func(context *cli.Context) error {
 		if context.GlobalBool("debug") {