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>

2 files changed, 42 insertions, 34 deletions

diff --git a/libpod/container_api.go b/libpod/container_api.go
index 00467d2bf..c6e478846 100644
--- a/libpod/container_api.go
+++ b/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
diff --git a/libpod/container_internal_linux.go b/libpod/container_internal_linux.go
index 77f607f0b..399220b9a 100644
--- a/libpod/container_internal_linux.go
+++ b/libpod/container_internal_linux.go
@@ -510,41 +510,44 @@ 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")
-	rootfsDiffFile, err := os.Create(rootfsDiffPath)
-	if err != nil {
-		return errors.Wrapf(err, "error creating root file-system diff file %q", rootfsDiffPath)
-	}
-	tarStream, err := c.runtime.GetDiffTarStream("", c.ID())
-	if err != nil {
-		return errors.Wrapf(err, "error exporting root file-system diff to %q", rootfsDiffPath)
-	}
-	_, err = io.Copy(rootfsDiffFile, tarStream)
-	if err != nil {
-		return errors.Wrapf(err, "error exporting root file-system diff to %q", rootfsDiffPath)
+	if !ignoreRootfs {
+		rootfsDiffFile, err := os.Create(rootfsDiffPath)
+		if err != nil {
+			return errors.Wrapf(err, "error creating root file-system diff file %q", rootfsDiffPath)
+		}
+		tarStream, err := c.runtime.GetDiffTarStream("", c.ID())
+		if err != nil {
+			return errors.Wrapf(err, "error exporting root file-system diff to %q", rootfsDiffPath)
+		}
+		_, err = io.Copy(rootfsDiffFile, tarStream)
+		if err != nil {
+			return errors.Wrapf(err, "error exporting root file-system diff to %q", rootfsDiffPath)
+		}
+		tarStream.Close()
+		rootfsDiffFile.Close()
+		includeFiles = append(includeFiles, "rootfs-diff.tar")
 	}
-	tarStream.Close()
-	rootfsDiffFile.Close()
-
 
 	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
 		}
 	}
@@ -816,17 +819,19 @@ func (c *Container) restore(ctx context.Context, options ContainerCheckpointOpti
 	}
 
 	// Before actually restarting the container, apply the root file-system changes
-	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
-		rootfsDiffFile, err := os.Open(rootfsDiffPath)
-		if err != nil {
-			return errors.Wrapf(err, "Failed to open root file-system diff file %s", rootfsDiffPath)
-		}
-		if err := c.runtime.ApplyDiffTarStream(c.ID(), rootfsDiffFile); err != nil {
-			return errors.Wrapf(err, "Failed to apply root file-system diff file %s", rootfsDiffPath)
+	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
+			rootfsDiffFile, err := os.Open(rootfsDiffPath)
+			if err != nil {
+				return errors.Wrapf(err, "Failed to open root file-system diff file %s", rootfsDiffPath)
+			}
+			if err := c.runtime.ApplyDiffTarStream(c.ID(), rootfsDiffFile); err != nil {
+				return errors.Wrapf(err, "Failed to apply root file-system diff file %s", rootfsDiffPath)
+			}
+			rootfsDiffFile.Close()
 		}
-		rootfsDiffFile.Close()
 	}
 
 	if err := c.ociRuntime.createContainer(c, c.config.CgroupParent, &options); err != nil {