diff --git a/pkg/kubelet/container/runtime.go b/pkg/kubelet/container/runtime.go
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+++ b/pkg/kubelet/container/runtime.go
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+/*
+Copyright 2015 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package container
+
+import (
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/kubelet/volume"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/types"
+)
+
+// Runtime interface defines the interfaces that should be implemented
+// by a container runtime.
+type Runtime interface {
+	// Version returns a map of version information of the container runtime.
+	Version() (map[string]string, error)
+	// GetPods returns a list containers group by pods. The boolean parameter
+	// specifies whether the runtime returns all containers including those already
+	// exited and dead containers (used for garbage collection).
+	GetPods(all bool) ([]*Pod, error)
+	// RunPod starts all the containers of a pod within a namespace.
+	RunPod(*api.Pod, map[string]volume.Interface) error
+	// KillPod kills all the containers of a pod.
+	KillPod(*api.Pod) error
+	// RunContainerInPod starts a container within the same namespace of a pod.
+	RunContainerInPod(api.Container, *api.Pod, map[string]volume.Interface) error
+	// KillContainerInPod kills a container in the pod.
+	KillContainerInPod(api.Container, *api.Pod) error
+	// GetPodStatus retrieves the status of the pod, including the information of
+	// all containers in the pod.
+	GetPodStatus(*Pod) (api.PodStatus, error)
+	// GetContainers returns all containers on the node, including those are
+	// not managed by kubelet. If 'all' is false, then only running containers
+	// are returned.
+	GetContainers(all bool) ([]*Container, error)
+	// TODO(yifan): Pull/Remove images
+}
+
+// Pod is a group of containers, with the status of the pod.
+type Pod struct {
+	// The ID of the pod, which can be used to retrieve a particular pod
+	// from the pod list returned by GetPods().
+	ID types.UID
+	// The name and namespace of the pod, which is readable by human.
+	Name      string
+	Namespace string
+	// List of containers that belongs to this pod. It may contain only
+	// running containers, or mixed with dead ones (when GetPods(true)).
+	Containers []*Container
+	// The status of the pod.
+	// TODO(yifan): Inspect and get the statuses for all pods can be expensive,
+	// maybe we want to get one pod's status at a time (e.g. GetPodStatus()
+	// for the particular pod after we GetPods()).
+	Status api.PodStatus
+}
+
+// Container provides the runtime information for a container, such as ID, hash,
+// status of the container.
+type Container struct {
+	// The ID of the container, used by the container runtime to identify
+	// a container.
+	ID types.UID
+	// The name of the container, which should be the same as specified by
+	// api.Container.
+	Name string
+	// The image name of the container.
+	Image string
+	// Hash of the container, used for comparison. Optional for containers
+	// not managed by kubelet.
+	Hash uint64
+}