Mastering Kubernetes: A Guide on How to SSH into Kubernetes Pods

Kubernetes has revolutionized container orchestration, enabling scalable and resilient applications. While it abstracts away much of the underlying infrastructure complexity, there are times when direct access to a pod is essential for debugging or maintenance. In this guide, we'll explore the process of SSHing into a Kubernetes pod step by step.

Prerequisites:

Before diving into the SSH process, ensure the following:

1. kubectl Installed: Make sure you have kubectl installed on your local machine.
2. Access Permissions: Ensure you have the necessary permissions to execute commands on the target pod.

Step 1: Identify the Pod:

Use the following command to list all pods in your Kubernetes cluster:

kubectl get pods

Identify the pod you want to access from the list.

Step 2: Get Pod's Namespace:

Run the following command to determine the namespace of your pod:

kubectl get pods <pod-name> -o=jsonpath='{.metadata.namespace}'

Step 3: Generate SSH Key Pair:

Generate an SSH key pair if you don't have one. This will be used for authentication.

ssh-keygen -t rsa -b 2048

Step 4: Copy Public Key to Pod:

Copy the public key to the pod using kubectl cp:

kubectl cp ~/.ssh/id_rsa.pub <namespace>/<pod-name>:/tmp/id_rsa.pub

Step 5: SSH into the Pod:

Now, SSH into the pod using the copied public key:

kubectl exec -it <pod-name> --namespace=<namespace> -- /bin/sh

Step 6: Install SSH Server (if needed):

If the pod doesn't have an SSH server installed, you might need to install one. For example, using apk for Alpine Linux:

apk update && apk add openssh

Step 7: Configure SSH Access:

Add the copied public key to the authorized keys file:

cat /tmp/id_rsa.pub >> ~/.ssh/authorized_keys

Step 8: SSH into the Pod (Again):

Now, SSH into the pod without a password prompt:

kubectl exec -it <pod-name> --namespace=<namespace> -- /bin/sh

Congratulations! You're now inside the Kubernetes pod.

More Examples:

Example 1: SSH with Specific User:

Specify the username when executing the kubectl exec command:

kubectl exec -it <pod-name> --namespace=<namespace> -- /bin/sh -c 'su - <username>'

Example 2: SSH into a Pod with Multiple Containers:

If your pod has multiple containers, choose the desired container:

kubectl exec -it <pod-name> -c <container-name> --namespace=<namespace> -- /bin/sh