Kubernetes Port Forward Command: A Comprehensive Guide

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Introduction

In this lab, you will learn how to use the Kubernetes port-forward command to forward a local port to a port on a pod. You will start with simple examples and gradually progress to more complex scenarios.

Forwarding a Local Port to a Pod

In this step, you will learn how to forward a local port to a port on a pod.

Start by creating a deployment with one replica and an Nginx container:

   kubectl create deployment nginx --image=nginx --replicas=1

Wait for the pod to become ready:

   kubectl wait --for=condition=Ready pod -l app=nginx

Use the kubectl port-forward command to forward a local port to the pod:

   kubectl port-forward < pod_name > 19000:80

Replace <pod_name> with the name of the pod created in step 1, and you can get the <pod_name> with the kubectl get pod -l app=nginx command.

Open a web browser and go to http://localhost:19000 to view the Nginx welcome page.

Forwarding Multiple Local Ports to a Pod

In this step, you will learn how to forward multiple local ports to a pod.

Use the kubectl port-forward command to forward multiple local ports to the pod:

   kubectl port-forward 19443:443 < pod_name > 19080:80

Replace <pod_name> with the name of the pod created in step 1, and you can get the <pod_name> with the kubectl get pod -l app=nginx command.

Open another terminal and use the ss command at the Linux command line to see if ports 19080 and 19443 are on the host.

Forwarding a Local Port to a Pod with Multiple Containers

In this step, you will learn how to forward a local port to a specific container in a pod with multiple containers.

Create a pod with two containers: Nginx and BusyBox:

   cat << EOF | kubectl apply -f -
   apiVersion: v1
   kind: Pod
   metadata:
     name: nginx-busybox
   spec:
     containers:
     - name: nginx
       image: nginx
     - name: busybox
       image: busybox
       command:
         - sleep
         - "3600"
   EOF

Wait for the pod to become ready:

   kubectl wait --for=condition=Ready pod nginx

Use the kubectl port-forward command to forward a local port to the Nginx container:

   kubectl port-forward nginx-busybox 19001:80

Open a web browser and go to http://localhost:19001 to view the Nginx welcome page.

Using Port-Forward with Kubernetes Services

In this step, you will learn how to use the kubectl port-forward command with Kubernetes services.

Create a service for the Nginx deployment:

   kubectl expose deployment nginx --port=80 --type=ClusterIP

Use the kubectl port-forward command to forward a local port to the service:

   kubectl port-forward service/nginx 20000:80

Open a web browser and go to http://localhost:20000 to view the Nginx welcome page.

Summary

Congratulations, you have successfully completed the Kubernetes port-forward command lab! In this lab, you learned how to forward a local port to a pod, forward multiple local ports to a pod, forward a pod port to a local port, forward a local port to a specific container in a pod with multiple containers, and use the kubectl port-forward command with Kubernetes services. These skills are essential for debugging issues in a Kubernetes cluster.