80 lines
2.9 KiB
Markdown
80 lines
2.9 KiB
Markdown
---
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---
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{% assign concept="Pod" %}
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{% capture what_is %}
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A pod is the vehicle for running containers in Kubernetes. A pod consists of:
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- One or more containers
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- An IP address that is unique within the cluster
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- Optionally: Environment variables, storage volumes, and enterprise features (such as health checking)
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Resources are shared amongst containers in the pod. Containers within a pod also share an IP address and port space, and can find each other via localhost, or interprocess communications (such as semaphores).
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{: style="max-width: 25%" }
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{% comment %}https://drive.google.com/open?id=1pQe4-s76fqyrzB8f3xoJo4MPLNVoBlsE1tT9MyLNINg{% endcomment %}
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{% endcapture %}
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{% capture when_to_use %}
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Pods are used any time you need a container to be run. However, they are rarely created by a user, and are instead automatically created by controllers such as jobs, replication controllers, deployments, daemon set. The following table describes the strategy each controller uses to create pods.
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| Controller | Usage Strategy |
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|------------|----------------|
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| Deployment | For running pods as a continuous and healthy application |
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| Replication Controller | Used for the same purpose as Deployments (superseded Replication Controllers) |
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| Jobs | For running pods "to completion" (which are then shut down) |
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| Daemon Set | Mainly for performing operations on any nodes that match given parameters |
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{% endcapture %}
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{% capture when_not_to_use %}
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Do not use pods directly. Pods should always be managed by a controller.
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{% endcapture %}
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{% capture status %}
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To retrieve the status of a pod, run the following command:
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```shell
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kubectl get pod <name>
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```
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| Return Value | Description |
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|--------------|-------------|
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| `READY` | Describes the number of containers that are ready to recieve traffic. |
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| `STATUS` | A value from the `PodPhase` enum describing the current status of the pod. Can be `Running`, `Pending`, `Succeeded`, `Failed`, and `Unknown`. |
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TODO: Link to refpage for `kubectl get pod`
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To get a full description of a pod, including past events, run the following command:
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```shell
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kubectl describe pod <name>
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```
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TODO: Link to refpage for `kubectl describe pod`
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#### Possible status results
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| Value | Description |
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|------------|----------------|
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| Deployment | For running pods as a continuous and healthy application |
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| Replication Controller | Used for the same purpose as Deployments (superseded Replication Controllers) |
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| Jobs | For running pods "to completion" (which are then shut down) |
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| Daemon Set | Mainly for performing operations on any nodes that match given parameters |
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{% endcapture %}
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{% capture usage %}
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Pods are defined when configuring the controller of your choice. In controller specifications,
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the parts that define the contents of the pod are inside the `template:` section.
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```yaml
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YAML EXAMPLE HERE
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```
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{% endcapture %}
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{% include templates/concept-overview.md %} |