Configuring a Kubernetes Pod as a Jenkins Agent

Jenkins is an automation server that plays a crucial role in coordinating CI/CD pipelines, but traditional Jenkins agents have limitations in scalability and flexibility. Kubernetes, a container orchestration platform, can be used to run Jenkins agents as pods, enabling dynamic scaling, optimized resource usage, and simplified CI/CD workflows.

Prerequisites

Access to a Jenkins instance

A running Kubernetes cluster

Kubernetes services started

Create a simple deployment file that launches a pod and a service.

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: demo
  labels:
    app: demo
    color: green
spec:
  replicas: 1
  selector:
    matchLabels:
      app: demo
  template:
    metadata:
      labels:
        app: demo
        color: green
    spec:
      containers:
        - name: demo
          image: ubuntu18:latest
          command: ["/usr/sbin/sshd","-D"]
          imagePullPolicy: IfNotPresent
          volumeMounts:
            - name: home
              mountPath: /home/
          ports:
            - containerPort: 22
      volumes:
        - name: home
          hostPath:
            path: /home/demo/
---
apiVersion: v1
kind: Service
metadata:
  name: demo-service
spec:
  ports:
    - port: 2222
      targetPort: 22
      nodePort: 32222
  selector:
    app: demo
  sessionAffinity: None
  type: NodePort

The above file creates a pod named "demo" from the base image ubuntu18 , runs /usr/sbin/sshd -D to start an SSH daemon in debug mode, mounts the host's /home/demo directory into the pod, opens port 22 for SSH, and creates a NodePort service demo-service exposing port 32222 to the outside of the Kubernetes cluster.

Run the following command to launch the pod and service:

kubectl apply -f <yaml_file_name>

Verify that the pod and service started successfully with:

kubectl get deployments

Configure Jenkins Agent

In the Jenkins console, navigate to Manage Jenkins → Manage Nodes and Clouds → New Node , provide a node name, select Permanent Agent , and click Create . Then fill in the following details and save:

Remote root directory: /home/demo/ (dedicated to this node)

Launch method: Launch agents via SSH

Host: Public IP address of the Kubernetes host

Credentials: Credentials of the user used to start the container

Host key verification strategy: Non-verifying strategy

Port: 32222 (the NodePort opened for external access)

JavaPath: /usr/lib/jvm/java-11-openjdk-amd64/bin/java (path to OpenJDK)

After creating the node, start it so that the Kubernetes pod functions as a Jenkins agent. Screenshots in the original article illustrate the node details and the final configuration.