Add support for checkpoint image

This is an enhancement proposal for the checkpoint / restore feature of
Podman that enables container migration across multiple systems with
standard image distribution infrastructure.

A new option `--create-image <image>` has been added to the
`podman container checkpoint` command. This option tells Podman to
create a container image.  This is a standard image with a single layer,
tar archive, that that contains all checkpoint files. This is similar to
the current approach with checkpoint `--export`/`--import`.

This image can be pushed to a container registry and pulled on a
different system.  It can also be exported locally with `podman image
save` and inspected with `podman inspect`. Inspecting the image would
display additional information about the host and the versions of
Podman, criu, crun/runc, kernel, etc.

`podman container restore` has also been extended to support image
name or ID as input.

Suggested-by: Adrian Reber <areber@redhat.com>
Signed-off-by: Radostin Stoyanov <radostin@redhat.com>

2 files changed, 8 insertions, 5 deletions

diff --git a/pkg/checkpoint/checkpoint_restore.go b/pkg/checkpoint/checkpoint_restore.go
index 270b5b6c4..396b521a1 100644
--- a/pkg/checkpoint/checkpoint_restore.go
+++ b/pkg/checkpoint/checkpoint_restore.go
@@ -22,9 +22,7 @@ import (
 
 // Prefixing the checkpoint/restore related functions with 'cr'
 
-// 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, restoreOptions entities.RestoreOptions) ([]*libpod.Container, error) {
+func CRImportCheckpointTar(ctx context.Context, runtime *libpod.Runtime, restoreOptions entities.RestoreOptions) ([]*libpod.Container, error) {
 	// First get the container definition from the
 	// tarball to a temporary directory
 	dir, err := ioutil.TempDir("", "checkpoint")
@@ -39,7 +37,12 @@ func CRImportCheckpoint(ctx context.Context, runtime *libpod.Runtime, restoreOpt
 	if err := crutils.CRImportCheckpointConfigOnly(dir, restoreOptions.Import); err != nil {
 		return nil, err
 	}
+	return CRImportCheckpoint(ctx, runtime, restoreOptions, dir)
+}
 
+// 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, restoreOptions entities.RestoreOptions, dir string) ([]*libpod.Container, error) {
 	// Load spec.dump from temporary directory
 	dumpSpec := new(spec.Spec)
 	if _, err := metadata.ReadJSONFile(dumpSpec, dir, metadata.SpecDumpFile); err != nil {
@@ -48,7 +51,7 @@ func CRImportCheckpoint(ctx context.Context, runtime *libpod.Runtime, restoreOpt
 
 	// Load config.dump from temporary directory
 	ctrConfig := new(libpod.ContainerConfig)
-	if _, err = metadata.ReadJSONFile(ctrConfig, dir, metadata.ConfigDumpFile); err != nil {
+	if _, err := metadata.ReadJSONFile(ctrConfig, dir, metadata.ConfigDumpFile); err != nil {
 		return nil, err
 	}
 
diff --git a/pkg/checkpoint/crutils/checkpoint_restore_utils.go b/pkg/checkpoint/crutils/checkpoint_restore_utils.go
index 6a8a7894a..76c868cee 100644
--- a/pkg/checkpoint/crutils/checkpoint_restore_utils.go
+++ b/pkg/checkpoint/crutils/checkpoint_restore_utils.go
@@ -54,7 +54,6 @@ func CRImportCheckpointConfigOnly(destination, input string) error {
 	options := &archive.TarOptions{
 		// Here we only need the files config.dump and spec.dump
 		ExcludePatterns: []string{
-			"volumes",
 			"ctr.log",
 			"artifacts",
 			stats.StatsDump,
@@ -62,6 +61,7 @@ func CRImportCheckpointConfigOnly(destination, input string) error {
 			metadata.DeletedFilesFile,
 			metadata.NetworkStatusFile,
 			metadata.CheckpointDirectory,
+			metadata.CheckpointVolumesDirectory,
 		},
 	}
 	if err = archive.Untar(archiveFile, destination, options); err != nil {