Add --ignore-rootfs option for checkpoint/restore

The newly added functionality to include the container's root
file-system changes into the checkpoint archive can now be explicitly
disabled. Either during checkpoint or during restore.

If a container changes a lot of files during its runtime it might be
more effective to migrated the root file-system changes in some other
way and to not needlessly increase the size of the checkpoint archive.

If a checkpoint archive does not contain the root file-system changes
information it will automatically be skipped. If the root file-system
changes are part of the checkpoint archive it is also possible to tell
Podman to ignore these changes.

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

cmd/podman/checkpoint.go

@@ -46,6 +46,7 @@ func init() {
 	flags.BoolVarP(&checkpointCommand.All, "all", "a", false, "Checkpoint all running containers")
 	flags.BoolVarP(&checkpointCommand.Latest, "latest", "l", false, "Act on the latest container podman is aware of")
 	flags.StringVarP(&checkpointCommand.Export, "export", "e", "", "Export the checkpoint image to a tar.gz")
+	flags.BoolVar(&checkpointCommand.IgnoreRootfs, "ignore-rootfs", false, "Do not include root file-system changes when exporting")
 	markFlagHiddenForRemoteClient("latest", flags)
 }
 

cmd/podman/cliconfig/config.go

@@ -92,6 +92,7 @@ type CheckpointValues struct {
 	All            bool
 	Latest         bool
 	Export         string
+	IgnoreRootfs   bool
 }
 
 type CommitValues struct {
@@ -433,6 +434,7 @@ type RestoreValues struct {
 	TcpEstablished bool
 	Import         string
 	Name           string
+	IgnoreRootfs   bool
 }
 
 type RmValues struct {

cmd/podman/restore.go

@@ -45,6 +45,7 @@ func init() {
 	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)")
+	flags.BoolVar(&restoreCommand.IgnoreRootfs, "ignore-rootfs", false, "Do not apply root file-system changes when importing from exported checkpoint")
 
 	markFlagHiddenForRemoteClient("latest", flags)
 }
@@ -60,6 +61,10 @@ func restoreCmd(c *cliconfig.RestoreValues, cmd *cobra.Command) error {
 	}
 	defer runtime.DeferredShutdown(false)
 
+	if c.Import == "" && c.IgnoreRootfs {
+		return errors.Errorf("--ignore-rootfs can only be used with --import")
+	}
+
 	if c.Import == "" && c.Name != "" {
 		return errors.Errorf("--name can only be used with --import")
 	}

completions/bash/podman

@@ -758,6 +758,7 @@ _podman_container_checkpoint() {
      -R
      --leave-running
      --tcp-established
+     --ignore-rootfs
      "
      case "$prev" in
         -e|--export)
@@ -870,6 +871,7 @@ _podman_container_restore() {
 	  -l
 	  --latest
 	  --tcp-established
+	  --ignore-rootfs
      "
      case "$prev" in
         -i|--import)

docs/podman-container-checkpoint.1.md

@@ -42,7 +42,15 @@ connections.
 
 Export the checkpoint to a tar.gz file. The exported checkpoint can be used
 to import the container on another system and thus enabling container live
-migration.
+migration. This checkpoint archive also includes all changes to the container's
+root file-system, if not explicitly disabled using **--ignore-rootfs**
+
+**--ignore-rootfs**
+
+This only works in combination with **--export, -e**. If a checkpoint is
+exported to a tar.gz file it is possible with the help of **--ignore-rootfs**
+to explicitly disable including changes to the root file-system into
+the checkpoint archive file.
 
 ## EXAMPLE
 

docs/podman-container-restore.1.md

@@ -60,6 +60,13 @@ address to the container it was using before checkpointing as each IP address ca
 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**.
 
+**--ignore-rootfs**
+
+This is only available in combination with **--import, -i**. If a container is restored
+from a checkpoint tar.gz file it is possible that it also contains all root file-system
+changes. With **--ignore-rootfs** it is possible to explicitly disable applying these
+root file-system changes to the restored container.
+
 ## EXAMPLE
 
 podman container restore mywebserver

libpod/container_api.go

@@ -799,6 +799,9 @@ type ContainerCheckpointOptions struct {
 	// checkpoint archive a new name should be used for the
 	// restored container
 	Name string
+	// IgnoreRootfs tells the API to not export changes to
+	// the container's root file-system (or to not import)
+	IgnoreRootfs bool
 }
 
 // Checkpoint checkpoints a container

libpod/container_internal_linux.go

@@ -510,14 +510,23 @@ func (c *Container) addNamespaceContainer(g *generate.Generator, ns LinuxNS, ctr
 	return nil
 }
 
-func (c *Container) exportCheckpoint(dest string) (err error) {
+func (c *Container) exportCheckpoint(dest string, ignoreRootfs bool) (err error) {
 	if (len(c.config.NamedVolumes) > 0) || (len(c.Dependencies()) > 0) {
 		return errors.Errorf("Cannot export checkpoints of containers with named volumes or dependencies")
 	}
 	logrus.Debugf("Exporting checkpoint image of container %q to %q", c.ID(), dest)
 
+	includeFiles := []string{
+		"checkpoint",
+		"artifacts",
+		"ctr.log",
+		"config.dump",
+		"spec.dump",
+		"network.status"}
+
 	// Get root file-system changes included in the checkpoint archive
 	rootfsDiffPath := filepath.Join(c.bundlePath(), "rootfs-diff.tar")
+	if !ignoreRootfs {
 		rootfsDiffFile, err := os.Create(rootfsDiffPath)
 		if err != nil {
 			return errors.Wrapf(err, "error creating root file-system diff file %q", rootfsDiffPath)
@@ -532,19 +541,13 @@ func (c *Container) exportCheckpoint(dest string) (err error) {
 		}
 		tarStream.Close()
 		rootfsDiffFile.Close()
-
+		includeFiles = append(includeFiles, "rootfs-diff.tar")
+	}
 
 	input, err := archive.TarWithOptions(c.bundlePath(), &archive.TarOptions{
 		Compression:      archive.Gzip,
 		IncludeSourceDir: true,
-		IncludeFiles: []string{
-			"checkpoint",
-			"artifacts",
-			"ctr.log",
-			"config.dump",
-			"spec.dump",
-			"rootfs-diff.tar",
-			"network.status"},
+		IncludeFiles:     includeFiles,
 	})
 
 	if err != nil {
@@ -627,7 +630,7 @@ func (c *Container) checkpoint(ctx context.Context, options ContainerCheckpointO
 	}
 
 	if options.TargetFile != "" {
-		if err = c.exportCheckpoint(options.TargetFile); err != nil {
+		if err = c.exportCheckpoint(options.TargetFile, options.IgnoreRootfs); err != nil {
 			return err
 		}
 	}
@@ -816,6 +819,7 @@ func (c *Container) restore(ctx context.Context, options ContainerCheckpointOpti
 	}
 
 	// Before actually restarting the container, apply the root file-system changes
+	if !options.IgnoreRootfs {
 		rootfsDiffPath := filepath.Join(c.bundlePath(), "rootfs-diff.tar")
 		if _, err := os.Stat(rootfsDiffPath); err == nil {
 			// Only do this if a rootfs-diff.tar actually exists
@@ -828,6 +832,7 @@ func (c *Container) restore(ctx context.Context, options ContainerCheckpointOpti
 			}
 			rootfsDiffFile.Close()
 		}
+	}
 
 	if err := c.ociRuntime.createContainer(c, c.config.CgroupParent, &options); err != nil {
 		return err

pkg/adapter/containers.go

@@ -524,6 +524,10 @@ func (r *LocalRuntime) Checkpoint(c *cliconfig.CheckpointValues) error {
 		KeepRunning:    c.LeaveRunning,
 		TCPEstablished: c.TcpEstablished,
 		TargetFile:     c.Export,
+		IgnoreRootfs:   c.IgnoreRootfs,
+	}
+	if c.Export == "" && c.IgnoreRootfs {
+		return errors.Errorf("--ignore-rootfs can only be used with --export")
 	}
 	if c.All {
 		containers, err = r.Runtime.GetRunningContainers()
@@ -560,6 +564,7 @@ func (r *LocalRuntime) Restore(ctx context.Context, c *cliconfig.RestoreValues)
 		TCPEstablished: c.TcpEstablished,
 		TargetFile:     c.Import,
 		Name:           c.Name,
+		IgnoreRootfs:   c.IgnoreRootfs,
 	}
 
 	filterFuncs = append(filterFuncs, func(c *libpod.Container) bool {

pkg/adapter/containers_remote.go

@@ -668,6 +668,9 @@ func (r *LocalRuntime) Checkpoint(c *cliconfig.CheckpointValues) error {
 	if c.Export != "" {
 		return errors.New("the remote client does not support exporting checkpoints")
 	}
+	if c.IgnoreRootfs {
+		return errors.New("the remote client does not support --ignore-rootfs")
+	}
 
 	var lastError error
 	ids, err := iopodman.GetContainersByContext().Call(r.Conn, c.All, c.Latest, c.InputArgs)
@@ -708,6 +711,9 @@ func (r *LocalRuntime) Restore(ctx context.Context, c *cliconfig.RestoreValues)
 	if c.Import != "" {
 		return errors.New("the remote client does not support importing checkpoints")
 	}
+	if c.IgnoreRootfs {
+		return errors.New("the remote client does not support --ignore-rootfs")
+	}
 
 	var lastError error
 	ids, err := iopodman.GetContainersByContext().Call(r.Conn, c.All, c.Latest, c.InputArgs)