Setup Dynamic Jenkins Agents in Kubernetes

Note This post is part of the DevOps Journey

We want to use a Kubernetes Cluster with Jenkins, so that Jenkins can fire up slaves in the cluster as required and perform the pipeline tasks. Instead of paying a lot of money for the Kubernetes Cluster, we will set it up locally using Kind.

Kubernetes Kind

Install

Install Kind with Homebrew:

brew install kind

Setup the Cluster

Create a yaml config file called kind-config.yaml for kind:

kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
networking:
  # WARNING: It is _strongly_ recommended that you keep this the default
  # (127.0.0.1) for security reasons. However it is possible to change this.
  apiServerAddress: "127.0.0.1"
  # By default the API server listens on a random open port.
  # You may choose a specific port but probably don't need to in most cases.
  # Using a random port makes it easier to spin up multiple clusters.
  apiServerPort: 53850

Create the cluster with kind-config.yaml file:

kind create cluster --config kind-config.yaml

Verify the cluster:

kubectl cluster-info --context kind-kind

In Kubernetes, namespaces provide a mechanism for isolating groups of resources within a single cluster. Create Namespace jenkins:

kubectl create namespace jenkins

A ServiceAccount will allow Jenkins to spin up the required slave pods as needed. Create a ServiceAccount named jenkins:

kubectl create serviceaccount jenkins --namespace=jenkins

Create a token for the ServiceAccount created above, this token will be used in the Jenkins for authentication:

kubectl create token jenkins --duration=999999h --namespace=jenkins

Copy this token, we will use it later in Jenkins.

Create admin role for the ServiceAccount:

kubectl create rolebinding jenkins-admin-binding --clusterrole=admin --serviceaccount=jenkins:jenkins --namespace=jenkins

Kubernetes cluster is setup to be used in Jenkins now.

Jenkins Setup

Now we’ll configure Jenkins to use our Kubernetes cluster for dynamic agent provisioning.

Install the Kubernetes Plugin

1. Go to Jenkins Dashboard → Manage Jenkins → Manage Plugins
2. Search for “Kubernetes” plugin and install it
3. Restart Jenkins if required

Configure Kubernetes Cloud

1. Navigate to Manage Jenkins → Configure System
2. Scroll down to “Cloud” section and click “Add a new cloud” → “Kubernetes”
3. Configure the following settings:

Kubernetes Cloud Details:

• Name: kubernetes
• Kubernetes URL: https://127.0.0.1:53850 (from our Kind cluster)
• Kubernetes Namespace: jenkins
• Credentials: Add → Jenkins → Secret text
  • Secret: (paste the token we created earlier)
  • ID: kubernetes-token
  • Description: Kubernetes ServiceAccount Token

Test Connection: Click “Test Connection” to verify the setup.

Create Pod Template

In the same Kubernetes cloud configuration:

1. Scroll down to “Pod Templates” and click “Add Pod Template”
2. Configure:
   • Name: jenkins-agent
   • Namespace: jenkins
   • Labels: jenkins-agent
   • Usage: “Use this node as much as possible”

Container Template:

• Name: jnlp
• Docker Image: jenkins/inbound-agent:latest
• Working Directory: /home/jenkins/agent
• Command to run: (leave empty)
• Arguments to pass: (leave empty)

Volume Mounts: Add if needed for Docker-in-Docker or specific tools.

Test Dynamic Agent

Create a simple pipeline to test:

pipeline {
    agent {
        kubernetes {
            label 'jenkins-agent'
        }
    }
    stages {
        stage('Test') {
            steps {
                sh 'echo "Running on Kubernetes agent"'
                sh 'kubectl version --client'
            }
        }
    }
}

The Jenkins agent pod will be created automatically in the Kubernetes cluster when the pipeline runs and destroyed after completion.

Verification

• Check pods in the jenkins namespace: kubectl get pods -n jenkins
• Monitor Jenkins logs for any connection issues
• Verify agents are created and destroyed dynamically

This setup provides scalable, on-demand Jenkins agents using Kubernetes resources efficiently.