cr: Add an ability to specify path for images

the emptye /ROOT/CTID/checkpoint file is created to
support the Checkpointed state.

Signed-off-by: Andrey Vagin <avagin@openvz.org>

container.go

@@ -115,13 +115,13 @@ type Container interface {
 	//
 	// errors:
 	// Systemerror - System error.
-	Checkpoint() error
+	Checkpoint(string) error
 
 	// Restore restores the checkpointed container to a running state using the criu(8) utiity.
 	//
 	// errors:
 	// Systemerror - System error.
-	Restore(*Process) error
+	Restore(*Process, string) error
 
 	// Destroys the container after killing all running processes.
 	//

container_linux.go

@@ -289,7 +289,7 @@ func (c *linuxContainer) checkCriuVersion() error {
 	return nil
 }
 
-func (c *linuxContainer) Checkpoint() error {
+func (c *linuxContainer) Checkpoint(imagePath string) error {
 	c.m.Lock()
 	defer c.m.Unlock()
 
@@ -297,12 +297,6 @@ func (c *linuxContainer) Checkpoint() error {
 		return err
 	}
 
-	imagePath := filepath.Join(c.root, "checkpoint")
-	// Since a container can be C/R'ed multiple times,
-	// the checkpoint directory may already exist.
-	if err := os.Mkdir(imagePath, 0655); err != nil && !os.IsExist(err) {
-		return err
-	}
 	workPath := filepath.Join(c.root, "criu.work")
 	if err := os.Mkdir(workPath, 0655); err != nil && !os.IsExist(err) {
 		return err
@@ -322,6 +316,11 @@ func (c *linuxContainer) Checkpoint() error {
 				"--ext-mount-map", fmt.Sprintf("%s:%s", m.Destination, m.Destination))
 		}
 	}
+	f, err := os.Create(filepath.Join(c.root, "checkpoint"))
+	if err != nil {
+		return err
+	}
+	f.Close()
 	addArgsFromEnv("CRIU_C", &args) // XXX debug
 	if err := exec.Command(c.criuPath, args...).Run(); err != nil {
 		return err
@@ -330,7 +329,7 @@ func (c *linuxContainer) Checkpoint() error {
 	return nil
 }
 
-func (c *linuxContainer) Restore(process *Process) error {
+func (c *linuxContainer) Restore(process *Process, imagePath string) error {
 	c.m.Lock()
 	defer c.m.Unlock()
 
@@ -338,13 +337,6 @@ func (c *linuxContainer) Restore(process *Process) error {
 		return err
 	}
 
-	pidfile := filepath.Join(c.root, "restoredpid")
-	// Make sure pidfile doesn't already exist from a
-	// previous restore.  Otherwise, CRIU will fail.
-	if err := os.Remove(pidfile); err != nil && !os.IsNotExist(err) {
-		return err
-	}
-
 	fds, err := syscall.Socketpair(syscall.AF_LOCAL, syscall.SOCK_SEQPACKET|syscall.SOCK_CLOEXEC, 0)
 	if err != nil {
 		return err
@@ -367,7 +359,6 @@ func (c *linuxContainer) Restore(process *Process) error {
 	}
 	defer workDir.Close()
 
-	imagePath := filepath.Join(c.root, "checkpoint")
 	imageDir, err := os.Open(imagePath)
 	if err != nil {
 		return err
@@ -563,7 +554,7 @@ func (c *linuxContainer) updateState(process parentProcess) error {
 		return err
 	}
 	defer f.Close()
-	os.RemoveAll(filepath.Join(c.root, "checkpoint"))
+	os.Remove(filepath.Join(c.root, "checkpoint"))
 	return json.NewEncoder(f).Encode(state)
 }
 

nsinit/checkpoint.go

@@ -1,19 +1,34 @@
 package main
 
-import "github.com/codegangsta/cli"
+import (
+	"fmt"
+	"os"
+
+	"github.com/codegangsta/cli"
+)
 
 var checkpointCommand = cli.Command{
 	Name:  "checkpoint",
 	Usage: "checkpoint a running container",
 	Flags: []cli.Flag{
 		cli.StringFlag{Name: "id", Value: "nsinit", Usage: "specify the ID for a container"},
+		cli.StringFlag{Name: "image-path", Value: "", Usage: "path where to save images"},
 	},
 	Action: func(context *cli.Context) {
+		imagePath := context.String("image-path")
+		if imagePath == "" {
+			fatal(fmt.Errorf("The --image-path option isn't specified"))
+		}
 		container, err := getContainer(context)
 		if err != nil {
 			fatal(err)
 		}
-		if err := container.Checkpoint(); err != nil {
+		// Since a container can be C/R'ed multiple times,
+		// the checkpoint directory may already exist.
+		if err := os.Mkdir(imagePath, 0655); err != nil && !os.IsExist(err) {
+			fatal(err)
+		}
+		if err := container.Checkpoint(imagePath); err != nil {
 			fatal(err)
 		}
 	},

nsinit/restore.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"fmt"
 	"os"
 	"os/exec"
 	"syscall"
@@ -15,8 +16,13 @@ var restoreCommand = cli.Command{
 	Usage: "restore a container from a previous checkpoint",
 	Flags: []cli.Flag{
 		cli.StringFlag{Name: "id", Value: "nsinit", Usage: "specify the ID for a container"},
+		cli.StringFlag{Name: "image-path", Value: "", Usage: "path where to save images"},
 	},
 	Action: func(context *cli.Context) {
+		imagePath := context.String("image-path")
+		if imagePath == "" {
+			fatal(fmt.Errorf("The --image-path option isn't specified"))
+		}
 		container, err := getContainer(context)
 		if err != nil {
 			fatal(err)
@@ -38,7 +44,7 @@ var restoreCommand = cli.Command{
 		if err := tty.attach(process); err != nil {
 			fatal(err)
 		}
-		err = container.Restore(process)
+		err = container.Restore(process, imagePath)
 		if err != nil {
 			fatal(err)
 		}