Add start subcommand in ctr.

Signed-off-by: Yanqiang Miao <miao.yanqiang@zte.com.cn>

cmd/ctr/main.go

@@ -81,6 +81,7 @@ containerd CLI
 		rootfsCommand,
 		runCommand,
 		snapshotCommand,
+		startCommand,
 		taskListCommand,
 		versionCommand,
 	}, extraCmds...)

cmd/ctr/start.go

@@ -0,0 +1,87 @@
+package main
+
+import (
+	"github.com/containerd/console"
+	"github.com/opencontainers/go-digest"
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+	"github.com/urfave/cli"
+)
+
+var startCommand = cli.Command{
+	Name:      "start",
+	Usage:     "start a container that have been created",
+	ArgsUsage: "CONTAINER",
+	Action: func(context *cli.Context) error {
+		var (
+			err error
+
+			ctx, cancel = appContext(context)
+			id          = context.Args().Get(0)
+		)
+
+		defer cancel()
+
+		if id == "" {
+			return errors.New("container id must be provided")
+		}
+		client, err := newClient(context)
+		if err != nil {
+			return err
+		}
+		container, err := client.LoadContainer(ctx, id)
+		if err != nil {
+			return err
+		}
+
+		spec, err := container.Spec()
+		if err != nil {
+			return err
+		}
+
+		tty := spec.Process.Terminal
+
+		task, err := newTask(ctx, container, digest.Digest(""), tty)
+		if err != nil {
+			return err
+		}
+		defer task.Delete(ctx)
+
+		statusC := make(chan uint32, 1)
+		go func() {
+			status, err := task.Wait(ctx)
+			if err != nil {
+				logrus.WithError(err).Error("wait process")
+			}
+			statusC <- status
+		}()
+		var con console.Console
+		if tty {
+			con = console.Current()
+			defer con.Reset()
+			if err := con.SetRaw(); err != nil {
+				return err
+			}
+		}
+		if err := task.Start(ctx); err != nil {
+			return err
+		}
+		if tty {
+			if err := handleConsoleResize(ctx, task, con); err != nil {
+				logrus.WithError(err).Error("console resize")
+			}
+		} else {
+			sigc := forwardAllSignals(ctx, task)
+			defer stopCatch(sigc)
+		}
+
+		status := <-statusC
+		if _, err := task.Delete(ctx); err != nil {
+			return err
+		}
+		if status != 0 {
+			return cli.NewExitError("", int(status))
+		}
+		return nil
+	},
+}