Added support to migrate containers

This commit adds an option to the checkpoint command to export a
checkpoint into a tar.gz file as well as importing a checkpoint tar.gz
file during restore. With all checkpoint artifacts in one file it is
possible to easily transfer a checkpoint and thus enabling container
migration in Podman. With the following steps it is possible to migrate
a running container from one system (source) to another (destination).

 Source system:
  * podman container checkpoint -l -e /tmp/checkpoint.tar.gz
  * scp /tmp/checkpoint.tar.gz destination:/tmp

 Destination system:
  * podman pull 'container-image-as-on-source-system'
  * podman container restore -i /tmp/checkpoint.tar.gz

The exported tar.gz file contains the checkpoint image as created by
CRIU and a few additional JSON files describing the state of the
checkpointed container.

Now the container is running on the destination system with the same
state just as during checkpointing. If the container is kept running
on the source system with the checkpoint flag '-R', the result will be
that the same container is running on two different hosts.

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

3 files changed, 14 insertions, 4 deletions

diff --git a/cmd/podman/checkpoint.go b/cmd/podman/checkpoint.go
index 234d683bb..86bc8b973 100644
--- a/cmd/podman/checkpoint.go
+++ b/cmd/podman/checkpoint.go
@@ -46,6 +46,7 @@ func init() {
 	flags.BoolVar(&checkpointCommand.TcpEstablished, "tcp-established", false, "Checkpoint a container with established TCP connections")
 	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")
 	markFlagHiddenForRemoteClient("latest", flags)
 }
 
@@ -64,6 +65,7 @@ func checkpointCmd(c *cliconfig.CheckpointValues) error {
 		Keep:           c.Keep,
 		KeepRunning:    c.LeaveRunning,
 		TCPEstablished: c.TcpEstablished,
+		TargetFile:     c.Export,
 	}
 	return runtime.Checkpoint(c, options)
 }
diff --git a/cmd/podman/cliconfig/config.go b/cmd/podman/cliconfig/config.go
index aaa4513d8..d742830ee 100644
--- a/cmd/podman/cliconfig/config.go
+++ b/cmd/podman/cliconfig/config.go
@@ -89,6 +89,7 @@ type CheckpointValues struct {
 	TcpEstablished bool
 	All            bool
 	Latest         bool
+	Export         string
 }
 
 type CommitValues struct {
@@ -426,6 +427,7 @@ type RestoreValues struct {
 	Keep           bool
 	Latest         bool
 	TcpEstablished bool
+	Import         string
 }
 
 type RmValues struct {
diff --git a/cmd/podman/restore.go b/cmd/podman/restore.go
index 36ae16183..828ae682f 100644
--- a/cmd/podman/restore.go
+++ b/cmd/podman/restore.go
@@ -24,10 +24,10 @@ var (
 			restoreCommand.InputArgs = args
 			restoreCommand.GlobalFlags = MainGlobalOpts
 			restoreCommand.Remote = remoteclient
-			return restoreCmd(&restoreCommand)
+			return restoreCmd(&restoreCommand, cmd)
 		},
 		Args: func(cmd *cobra.Command, args []string) error {
-			return checkAllAndLatest(cmd, args, false)
+			return checkAllAndLatest(cmd, args, true)
 		},
 		Example: `podman container restore ctrID
   podman container restore --latest
@@ -44,11 +44,12 @@ func init() {
 	flags.BoolVarP(&restoreCommand.Keep, "keep", "k", false, "Keep all temporary checkpoint files")
 	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)")
 
 	markFlagHiddenForRemoteClient("latest", flags)
 }
 
-func restoreCmd(c *cliconfig.RestoreValues) error {
+func restoreCmd(c *cliconfig.RestoreValues, cmd *cobra.Command) error {
 	if rootless.IsRootless() {
 		return errors.New("restoring a container requires root")
 	}
@@ -62,6 +63,11 @@ func restoreCmd(c *cliconfig.RestoreValues) error {
 	options := libpod.ContainerCheckpointOptions{
 		Keep:           c.Keep,
 		TCPEstablished: c.TcpEstablished,
+		TargetFile:     c.Import,
 	}
-	return runtime.Restore(c, options)
+
+	if (c.Import != "") && (c.All || c.Latest) {
+		return errors.Errorf("Cannot use --import and --all or --latest at the same time")
+	}
+	return runtime.Restore(getContext(), c, options)
 }