How to Change Image Pull Policy in Kubernetes

Kubernetes, the open-source container orchestration platform, has become a cornerstone in modern application deployment. Managing containerized applications efficiently is crucial, and understanding image pull policies is an integral part of this process. In this guide, we will delve into the intricacies of changing the image pull policy in Kubernetes, empowering you to optimize your containerized workloads.

Understanding Image Pull Policy:
Before we embark on the journey of changing the image pull policy, it's imperative to comprehend what this policy entails. In Kubernetes, the image pull policy dictates when to fetch the container images associated with your pods. The three primary policies are 'Always,' 'IfNotPresent,' and 'Never.' Each policy caters to different use cases and scenarios.

1. Checking the Current Image Pull Policy:
   To determine the current image pull policy for a deployment, pod, or replica set, you can use the following command:

   kubectl get deployment <deployment-name> -o=jsonpath='{.spec.template.spec.containers[0].imagePullPolicy}'
   

   Replace <deployment-name> with the name of your deployment. This command extracts the image pull policy from the deployment's specification.

2. Changing Image Pull Policy:
   To modify the image pull policy, you need to update the deployment or pod definition. Let's say you want to change the policy to 'IfNotPresent.' Use the following command:

   kubectl patch deployment <deployment-name> -p '{"spec":{"template":{"spec":{"containers":[{"name":"<container-name>","imagePullPolicy":"IfNotPresent"}]}}}}'
   

   Remember to replace <deployment-name> and <container-name> with your deployment and container names, respectively.

Step-by-Step Instructions:

1. Identify the Deployment:
   Begin by identifying the deployment for which you want to change the image pull policy. Execute:

   kubectl get deployments
   

   Choose the deployment you wish to modify.

2. Inspect Current Image Pull Policy:
   Run the command mentioned under "Checking the Current Image Pull Policy" to understand the current policy.

3. Update the Image Pull Policy:
   Utilize the command from "Changing Image Pull Policy" section, adjusting the policy as needed.

4. Verify the Changes:
   After updating the policy, verify the changes with:

   kubectl get deployment <deployment-name> -o=jsonpath='{.spec.template.spec.containers[0].imagePullPolicy}'
   

   Ensure that the image pull policy now reflects your modifications.

More Examples:

• If you want to set the policy to 'Always,' replace "imagePullPolicy":"IfNotPresent" with "imagePullPolicy":"Always" in the update command.
• For the 'Never' policy, use "imagePullPolicy":"Never" in the same command.