Make sure to prepare the kic volume after creation

The volume is created as empty, so make sure that we run a
container to do the initial copy of /var from the image.

This is to avoid race conditions later on, where the preload
starts to use the created volume for packing up the tarball.

pkg/drivers/kic/oci/oci.go

@@ -99,6 +99,10 @@ func PrepareContainerNode(p CreateParams) error {
 		return errors.Wrapf(err, "creating volume for %s container", p.Name)
 	}
 	glog.Infof("Successfully created a %s volume %s", p.OCIBinary, p.Name)
+	if err := prepareVolume(p.OCIBinary, p.Image, p.Name); err != nil {
+		return errors.Wrapf(err, "preparing volume for %s container", p.Name)
+	}
+	glog.Infof("Successfully prepared a %s volume %s", p.OCIBinary, p.Name)
 	return nil
 }
 

pkg/drivers/kic/oci/volumes.go

@@ -106,3 +106,14 @@ func createVolume(ociBin string, profile string, nodeName string) error {
 	}
 	return nil
 }
+
+// prepareVolume will copy the initial content of the mount point by starting a container to check the expected content
+func prepareVolume(ociBin string, imageName string, nodeName string) error {
+	cmdArgs := []string{"run", "--rm", "--entrypoint", "/usr/bin/test"}
+	cmdArgs = append(cmdArgs, "-v", fmt.Sprintf("%s:/var", nodeName), imageName, "-d", "/var/lib")
+	cmd := exec.Command(ociBin, cmdArgs...)
+	if _, err := runCmd(cmd); err != nil {
+		return err
+	}
+	return nil
+}