migration: add possibility to restore a container with a new name

The option to restore a container from an external checkpoint archive
(podman container restore -i /tmp/checkpoint.tar.gz) restores a
container with the same name and same ID as id had before checkpointing.

This commit adds the option '--name,-n' to 'podman container restore'.
With this option the restored container gets the name specified after
'--name,-n' and a new ID. This way it is possible to restore one
container multiple times.

If a container is restored with a new name Podman will not try to
request the same IP address for the container as it had during
checkpointing. This implicitly assumes that if a container is restored
from a checkpoint archive with a different name, that it will be
restored multiple times and restoring a container multiple times with
the same IP address will fail as each IP address can only be used once.

Signed-off-by: Adrian Reber <areber@redhat.com>

cmd/podman/cliconfig/config.go

@@ -428,6 +428,7 @@ type RestoreValues struct {
 	Latest         bool
 	TcpEstablished bool
 	Import         string
+	Name           string
 }
 
 type RmValues struct {

cmd/podman/restore.go

@@ -45,6 +45,7 @@ func init() {
 	flags.BoolVarP(&restoreCommand.Latest, "latest", "l", false, "Act on the latest container podman is aware of")
 	flags.BoolVar(&restoreCommand.TcpEstablished, "tcp-established", false, "Restore a container with established TCP connections")
 	flags.StringVarP(&restoreCommand.Import, "import", "i", "", "Restore from exported checkpoint archive (tar.gz)")
+	flags.StringVarP(&restoreCommand.Name, "name", "n", "", "Specify new name for container restored from exported checkpoint (only works with --import)")
 
 	markFlagHiddenForRemoteClient("latest", flags)
 }
@@ -64,6 +65,15 @@ func restoreCmd(c *cliconfig.RestoreValues, cmd *cobra.Command) error {
 		Keep:           c.Keep,
 		TCPEstablished: c.TcpEstablished,
 		TargetFile:     c.Import,
+		Name:           c.Name,
+	}
+
+	if c.Import == "" && c.Name != "" {
+		return errors.Errorf("--name can only used with --import")
+	}
+
+	if c.Name != "" && c.TcpEstablished {
+		return errors.Errorf("--tcp-established cannot be used with --name")
 	}
 
 	if (c.Import != "") && (c.All || c.Latest) {

completions/bash/podman

@@ -857,6 +857,8 @@ _podman_container_restore() {
      local options_with_args="
      -i
      --import
+     -n
+     --name
      "
      local boolean_options="
 	  -a

docs/podman-container-restore.1.md

@@ -48,6 +48,18 @@ Import a checkpoint tar.gz file, which was exported by Podman. This can be used
 to import a checkpointed container from another host. It is not necessary to specify
 a container when restoring from an exported checkpoint.
 
+**--name, -n**
+
+This is only available in combination with **--import, -i**. If a container is restored
+from a checkpoint tar.gz file it is possible to rename it with **--name, -n**. This
+way it is possible to restore a container from a checkpoint multiple times with different
+names.
+
+If the **--name, -n** option is used, Podman will not attempt to assign the same IP
+address to the container it was using before checkpointing as each IP address can only
+be used once and the restored container will have another IP address. This also means
+that **--name, -n** cannot be used in combination with **--tcp-established**.
+
 ## EXAMPLE
 
 podman container restore mywebserver

libpod/container_api.go

@@ -820,6 +820,10 @@ type ContainerCheckpointOptions struct {
 	// Import tells the API to read the checkpoint image from
 	// the filename set in TargetFile
 	TargetFile string
+	// Name tells the API that during restore from an exported
+	// checkpoint archive a new name should be used for the
+	// restored container
+	Name string
 }
 
 // Checkpoint checkpoints a container

libpod/container_internal_linux.go

@@ -681,7 +681,13 @@ func (c *Container) restore(ctx context.Context, options ContainerCheckpointOpti
 	// Read network configuration from checkpoint
 	// Currently only one interface with one IP is supported.
 	networkStatusFile, err := os.Open(filepath.Join(c.bundlePath(), "network.status"))
-	if err == nil {
+	// If the restored container should get a new name, the IP address of
+	// the container will not be restored. This assumes that if a new name is
+	// specified, the container is restored multiple times.
+	// TODO: This implicit restoring with or without IP depending on an
+	//       unrelated restore parameter (--name) does not seem like the
+	//       best solution.
+	if err == nil && options.Name == "" {
 		// The file with the network.status does exist. Let's restore the
 		// container with the same IP address as during checkpointing.
 		defer networkStatusFile.Close()

libpod/runtime_ctr.go

@@ -76,6 +76,14 @@ func (r *Runtime) initContainerVariables(rSpec *spec.Spec, config *ContainerConf
 		if err := JSONDeepCopy(config, ctr.config); err != nil {
 			return nil, errors.Wrapf(err, "error copying container config for restore")
 		}
+		// If the ID is empty a new name for the restored container was requested
+		if ctr.config.ID == "" {
+			ctr.config.ID = stringid.GenerateNonCryptoID()
+			// Fixup ExitCommand with new ID
+			ctr.config.ExitCommand[len(ctr.config.ExitCommand)-1] = ctr.config.ID
+		}
+		// Reset the log path to point to the default
+		ctr.config.LogPath = ""
 	}
 
 	ctr.config.Spec = new(spec.Spec)
@@ -189,11 +197,16 @@ func (r *Runtime) setupContainer(ctx context.Context, ctr *Container, restore bo
 	}
 
 	if restore {
-		// Remove information about /dev/shm mount
+		// Remove information about bind mount
 		// for new container from imported checkpoint
 		g := generate.Generator{Config: ctr.config.Spec}
 		g.RemoveMount("/dev/shm")
 		ctr.config.ShmDir = ""
+		g.RemoveMount("/etc/resolv.conf")
+		g.RemoveMount("/etc/hostname")
+		g.RemoveMount("/etc/hosts")
+		g.RemoveMount("/run/.containerenv")
+		g.RemoveMount("/run/secrets")
 	}
 
 	// Set up storage for the container

pkg/adapter/checkpoint_restore.go

@@ -41,7 +41,7 @@ func crImportFromJSON(filePath string, v interface{}) error {
 
 // crImportCheckpoint it the function which imports the information
 // from checkpoint tarball and re-creates the container from that information
-func crImportCheckpoint(ctx context.Context, runtime *libpod.Runtime, input string) ([]*libpod.Container, error) {
+func crImportCheckpoint(ctx context.Context, runtime *libpod.Runtime, input string, name string) ([]*libpod.Container, error) {
 	// First get the container definition from the
 	// tarball to a temporary directory
 	archiveFile, err := os.Open(input)
@@ -85,6 +85,18 @@ func crImportCheckpoint(ctx context.Context, runtime *libpod.Runtime, input stri
 		return nil, errors.Errorf("Cannot import checkpoints of containers with named volumes or dependencies")
 	}
 
+	ctrID := config.ID
+	newName := false
+
+	// Check if the restored container gets a new name
+	if name != "" {
+		config.ID = ""
+		config.Name = name
+		newName = true
+	}
+
+	ctrName := config.Name
+
 	// The code to load the images is copied from create.go
 	var writer io.Writer
 	// In create.go this only set if '--quiet' does not exist.
@@ -110,6 +122,24 @@ func crImportCheckpoint(ctx context.Context, runtime *libpod.Runtime, input stri
 		return nil, nil
 	}
 
+	containerConfig := container.Config()
+	if containerConfig.Name != ctrName {
+		return nil, errors.Errorf("Name of restored container (%s) does not match requested name (%s)", containerConfig.Name, ctrName)
+	}
+
+	if newName == false {
+		// Only check ID for a restore with the same name.
+		// Using -n to request a new name for the restored container, will also create a new ID
+		if containerConfig.ID != ctrID {
+			return nil, errors.Errorf("ID of restored container (%s) does not match requested ID (%s)", containerConfig.ID, ctrID)
+		}
+	}
+
+	// Check if the ExitCommand points to the correct container ID
+	if containerConfig.ExitCommand[len(containerConfig.ExitCommand)-1] != containerConfig.ID {
+		return nil, errors.Errorf("'ExitCommandID' uses ID %s instead of container ID %s", containerConfig.ExitCommand[len(containerConfig.ExitCommand)-1], containerConfig.ID)
+	}
+
 	containers = append(containers, container)
 	return containers, nil
 }

pkg/adapter/containers.go

@@ -539,7 +539,7 @@ func (r *LocalRuntime) Restore(ctx context.Context, c *cliconfig.RestoreValues,
 	})
 
 	if c.Import != "" {
-		containers, err = crImportCheckpoint(ctx, r.Runtime, c.Import)
+		containers, err = crImportCheckpoint(ctx, r.Runtime, c.Import, c.Name)
 	} else if c.All {
 		containers, err = r.GetContainers(filterFuncs...)
 	} else {

test/e2e/checkpoint_test.go

@@ -376,9 +376,20 @@ var _ = Describe("Podman checkpoint", func() {
 		Expect(podmanTest.NumberOfContainersRunning()).To(Equal(1))
 		Expect(podmanTest.GetContainerStatus()).To(ContainSubstring("Up"))
 
+		// Restore container a second time with different name
+		result = podmanTest.Podman([]string{"container", "restore", "-i", "/tmp/checkpoint.tar.gz", "-n", "restore_again"})
+		result.WaitWithDefaultTimeout()
+
+		Expect(result.ExitCode()).To(Equal(0))
+		Expect(podmanTest.NumberOfContainersRunning()).To(Equal(2))
+		Expect(podmanTest.GetContainerStatus()).To(ContainSubstring("Up"))
+
 		result = podmanTest.Podman([]string{"rm", "-fa"})
 		result.WaitWithDefaultTimeout()
 		Expect(result.ExitCode()).To(Equal(0))
 		Expect(podmanTest.NumberOfContainersRunning()).To(Equal(0))
+
+		// Remove exported checkpoint
+		os.Remove("/tmp/checkpoint.tar.gz")
 	})
 })