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Add a simple pod manifest to pod overview #5986

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Oct 25, 2017
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Add a simple pod manifest to pod overview #5986

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16 changes: 16 additions & 0 deletions docs/concepts/workloads/pods/pod-overview.md
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Expand Up @@ -74,6 +74,22 @@ In general, Controllers use a Pod Template that you provide to create the Pods f
Pod templates are pod specifications which are included in other objects, such as
[Replication Controllers](/docs/concepts/workloads/controllers/replicationcontroller/), [Jobs](/docs/concepts/jobs/run-to-completion-finite-workloads/), and
[DaemonSets](/docs/concepts/workloads/controllers/daemonset/). Controllers use Pod Templates to make actual pods.
The sample below is a simple manifest for a Pod which contains a container that prints
a message.

```yaml
apiVersion: v1
kind: Pod
metadata:
name: myapp-pod
labels:
app: myapp
spec:
containers:
- name: myapp-container
image: busybox
command: ['sh', '-c', 'echo Hello Kubernetes! && sleep 3600']
```

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Suggestion: Call this a Pod manifest instead of a Pod template. Otherwise, readers could confuse this with PodTemplate.

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+1

Rather than specifying the current desired state of all replicas, pod templates are like cookie cutters. Once a cookie has been cut, the cookie has no relationship to the cutter. There is no quantum entanglement. Subsequent changes to the template or even switching to a new template has no direct effect on the pods already created. Similarly, pods created by a replication controller may subsequently be updated directly. This is in deliberate contrast to pods, which do specify the current desired state of all containers belonging to the pod. This approach radically simplifies system semantics and increases the flexibility of the primitive.

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