K8S Mastering: Debug environment variables for a pod

To debug environment variables for a pod in a MicroK8s cluster, you can use a script that retrieves the pod’s environment variables using kubectl exec. This script allows you to inspect the environment variables of all containers in the pod or a specific container.

Here’s the script:

Script: debug-pod-env.sh

#!/bin/bash

# Function to display usage
usage() {
  echo "Usage: $0 -n <namespace> -p <pod-name> [-c <container-name>]"
  echo
  echo "  -n <namespace>       Kubernetes namespace of the pod"
  echo "  -p <pod-name>        Name of the pod"
  echo "  -c <container-name>  (Optional) Name of the container in the pod"
  echo
  echo "Example: $0 -n default -p my-pod"
  echo "         $0 -n default -p my-pod -c my-container"
  exit 1
}

# Check if kubectl is available
if ! command -v kubectl &>/dev/null; then
  echo "kubectl is required but not installed. Please install kubectl."
  exit 1
fi

# Parse command-line arguments
while getopts "n:p:c:" opt; do
  case ${opt} in
    n)
      namespace=${OPTARG}
      ;;
    p)
      pod_name=${OPTARG}
      ;;
    c)
      container_name=${OPTARG}
      ;;
    *)
      usage
      ;;
  esac
done

# Validate required arguments
if [[ -z "${namespace}" || -z "${pod_name}" ]]; then
  usage
fi

# Fetch environment variables
echo "Fetching environment variables for pod: ${pod_name} in namespace: ${namespace}"
if [[ -z "${container_name}" ]]; then
  echo "No container name specified. Fetching for all containers..."
  kubectl -n "${namespace}" exec "${pod_name}" -- printenv
else
  echo "Fetching environment variables for container: ${container_name}"
  kubectl -n "${namespace}" exec "${pod_name}" -c "${container_name}" -- printenv
fi

Usage Instructions:

1. Save the script: Copy the script into a file, e.g., debug-pod-env.sh.
2. Make it executable: Run the following command: chmod +x debug-pod-env.sh
3. Run the script:
   • For all containers in the pod: ./debug-pod-env.sh -n <namespace> -p <pod-name>
   • For a specific container in the pod: ./debug-pod-env.sh -n <namespace> -p <pod-name> -c <container-name>

Example:

If you want to debug a pod named my-app-pod in the default namespace:

./debug-pod-env.sh -n default -p my-app-pod

To debug the environment variables of a container named my-container within the same pod:

./debug-pod-env.sh -n default -p my-app-pod -c my-container

Debug mongo database secrets

kubectl exec -it sample-node-app-6945c8c546 -- printenv | grep "MONGO"

./debug-pod-env.sh -n default -p sample-node-app-6945c8c546 | grep "MONGO"

This script leverages kubectl exec to run the printenv command inside the pod or container, allowing you to see the environment variables in real-time.