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---
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---
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{% capture overview %}
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This page shows how to define commands and arguments when you run a container
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in a Kubernetes Pod.
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{% endcapture %}
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{% capture prerequisites %}
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{% include task-tutorial-prereqs.md %}
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{% endcapture %}
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{% capture steps %}
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### Defining a command and arguments when you create a Pod
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When you create a Pod, you can define a command and arguments for the
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containers that run in the Pod. To define a command, include the `command`
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field in the configuration file. To define arguments for the command, include
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the `args` field in the configuration file. The command and arguments that
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you define cannot be changed after the Pod is created.
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The command and arguments that you define in the configuration file
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override the default command and arguments provided by the container image.
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If you define args, but do not define a command, the default command is used
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with your new arguments. For more information, see
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[Commands and Capabilities](/docs/user-guide/containers/).
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In this exercise, you create a Pod that runs one container. The configuration
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file for the Pod defines a command and two arguments:
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{% include code.html language="yaml" file="commands.yaml" ghlink="/docs/tasks/configure-pod-container/commands.yaml" %}
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1. Create a Pod based on the YAML configuration file:
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export REPO=https://raw.githubusercontent.com/kubernetes/kubernetes.github.io/master
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kubectl create -f $REPO/docs/tasks/configure-pod-container/commands.yaml
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1. List the running Pods:
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kubectl get pods
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The output shows that the container that ran in the command-demo Pod has
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completed.
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1. To see the output of the command that ran in the container, view the logs
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from the Pod:
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kubectl logs command-demo
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The output shows the values of the HOSTNAME and KUBERNETES_PORT environment
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variables:
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command-demo
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tcp://10.3.240.1:443
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### Using environment variables to define arguments
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In the preceding example, you defined the arguments directly by
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providing strings. As an alternative to providing strings directly,
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you can define arguments by using environment variables:
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env:
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- name: MESSAGE
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value: "hello world"
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command: ["/bin/echo"]
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args: ["$(MESSAGE)"]
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This means you can define an argument for a Pod using any of
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the techniques available for defining environment variables, including
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[ConfigMaps](/docs/user-guide/configmap/)
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and
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[Secrets](/docs/user-guide/secrets/).
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NOTE: The environment variable appears in parentheses, `"$(VAR)"`. This is
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required for the variable to be expanded in the `command` or `args` field.
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### Running a command in a shell
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In some cases, you need your command to run in a shell. For example, your
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command might consist of several commands piped together, or it might be a shell
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script. To run your command in a shell, wrap it like this:
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command: ["/bin/sh"]
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args: ["-c", "while true; do echo hello; sleep 10;done"]
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{% endcapture %}
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{% capture whatsnext %}
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* Learn more about [containers and commands](/docs/user-guide/containers/).
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* Learn more about [configuring containers](/docs/user-guide/configuring-containers/).
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* Learn more about [running commands in a container](/docs/user-guide/getting-into-containers/).
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* See [Container](/docs/api-reference/v1/definitions/#_v1_container).
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{% endcapture %}
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{% include templates/task.md %}
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Phillip Wittrock