Commands and Arguments in Kubernetes

In this tutorial, you’ll learn how to configure commands and arguments in a Kubernetes Pod. We’ll use a simple ubuntu-sleeper image that demonstrates how ENTRYPOINT and CMD from a Dockerfile map to the command and args fields in a Pod spec.

Table of Contents

1. Recap: ubuntu-sleeper Docker Image
2. Create a Pod with the Default Command
3. Override CMD with args
4. Override ENTRYPOINT with command
5. Summary & Mapping Table
6. References

Recap: ubuntu-sleeper Docker Image

We built a minimal Docker image called ubuntu-sleeper:

FROM ubuntu
ENTRYPOINT ["sleep"]
CMD ["5"]

• Running without extra arguments uses the default sleep duration (5 seconds):

  docker run --name ubuntu-sleeper ubuntu-sleeper
  

• Providing an argument overrides CMD (for example, sleep 10):

  docker run --name ubuntu-sleeper ubuntu-sleeper 10
  

In Docker CLI, anything after the image name replaces the CMD instruction.

Create a Pod with the Default Command

Here’s the simplest Pod manifest that runs sleep 5 by default:

apiVersion: v1
kind: Pod
metadata:
  name: ubuntu-sleeper-pod
spec:
  containers:
    - name: ubuntu-sleeper
      image: ubuntu-sleeper

Apply the Pod:

kubectl create -f pod-definition.yml

By default, Kubernetes uses the image’s ENTRYPOINT + CMD (sleep 5), and the container will exit after 5 seconds.

Override CMD with args

To change the sleep duration without touching the entrypoint, specify an args array in your Pod spec:

apiVersion: v1
kind: Pod
metadata:
  name: ubuntu-sleeper-pod
spec:
  containers:
    - name: ubuntu-sleeper
      image: ubuntu-sleeper
      args: ["10"]

This runs sleep 10. Update the Pod:

kubectl apply -f pod-definition.yml

Override ENTRYPOINT with command

If you need to override both the entrypoint and its arguments, use the command field for the entrypoint and args for its parameters:

apiVersion: v1
kind: Pod
metadata:
  name: ubuntu-sleeper-pod
spec:
  containers:
    - name: ubuntu-sleeper
      image: ubuntu-sleeper
      command: ["sleep2.0"]
      args: ["10"]

• command replaces the Dockerfile ENTRYPOINT.
• args replaces the Dockerfile CMD.

Apply this configuration:

kubectl create -f pod-definition.yml

Summary & Mapping Table

The table below summarizes how Dockerfile instructions map to Kubernetes Pod spec fields:

Use these fields to precisely control the process invoked inside your containers.

References

• Kubernetes Official Documentation
• Dockerfile reference
• Managing Containers in Pods