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>

3 files changed, 25 insertions, 2 deletions

diff --git a/libpod/container_api.go b/libpod/container_api.go
index 72c4d7f37..c27cb85ea 100644
--- a/libpod/container_api.go
+++ b/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
diff --git a/libpod/container_internal_linux.go b/libpod/container_internal_linux.go
index d471d4191..4acc77afa 100644
--- a/libpod/container_internal_linux.go
+++ b/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()
diff --git a/libpod/runtime_ctr.go b/libpod/runtime_ctr.go
index 9d0bbf7e8..cf1f5701d 100644
--- a/libpod/runtime_ctr.go
+++ b/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