Using kubectl logs and exec

1. Introduction

Kubernetes is an open-source platform for automating deployment, scaling, and operations of application containers. Monitoring and logging are critical for troubleshooting and ensuring the health of applications running in a Kubernetes cluster. In this lesson, we will explore two essential commands: kubectl logs for viewing logs of your pods and kubectl exec for executing commands inside a container.

2. kubectl logs

The kubectl logs command retrieves logs from a container in a pod. This is essential for debugging issues in your applications.

2.1 Syntax

kubectl logs [POD_NAME] [-c CONTAINER_NAME] [OPTIONS]

2.2 Example Usage

kubectl logs my-pod
kubectl logs my-pod -c my-container
kubectl logs my-pod --previous

In this example:

• The first command fetches logs from the default container in my-pod.
• The second command fetches logs from a specific container my-container.
• The third command retrieves logs from the previous instance of the container if it has crashed.

2.3 Important Notes

3. kubectl exec

The kubectl exec command allows you to execute commands directly inside a running container. This is useful for debugging and troubleshooting.

3.1 Syntax

kubectl exec [POD_NAME] [-c CONTAINER_NAME] -- COMMAND [ARG...]

3.2 Example Usage

kubectl exec my-pod -- ls /app
kubectl exec my-pod -c my-container -- /bin/bash

In this example:

• The first command lists files in the /app directory of the my-pod.
• The second command opens a bash shell in the specified container.

3.3 Important Notes

4. Best Practices

• Integrate a centralized logging solution (e.g., ELK stack, Fluentd) for persistent log storage.
• Use kubectl logs with filters to narrow down logs based on time or severity.
• Limit the use of kubectl exec to troubleshooting; prefer automated solutions.
• Regularly monitor logs for anomalies to proactively address issues.

5. FAQ