Deploy Jenkins on Kubernetes using K3s

After spending countless hours experimenting with different Kubernetes distributions, I've found that K3s provides an excellent lightweight platform for running Jenkins. In this guide, I'll share my hands-on experience deploying Jenkins on K3s, including the challenges I faced and how I overcame them.

Prerequisites

Before we dive in, make sure you have:

A Linux server with at least 2 CPU cores and 4GB RAM
K3s installed on your server (Follow my detailed guide: How to Install K3s on Ubuntu)
kubectl command-line tool installed on your local machine
Basic knowledge of Kubernetes concepts

Setting Up Storage

Jenkins needs persistent storage to maintain its configuration and build history. Let's create a StorageClass and PersistentVolume:


cat <<EOF | kubectl apply -f -
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: local-path
provisioner: rancher.io/local-path
volumeBindingMode: WaitForFirstConsumer
reclaimPolicy: Retain
EOF

Creating a Jenkins Namespace

I always recommend isolating Jenkins in its own namespace for better resource management:

kubectl create namespace jenkins

Deploying Jenkins

Here's the Jenkins deployment configuration I've refined through multiple iterations:

cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  name: jenkins
  namespace: jenkins
spec:
  replicas: 1
  selector:
    matchLabels:
      app: jenkins
  template:
    metadata:
      labels:
        app: jenkins
    spec:
      containers:
      - name: jenkins
        image: jenkins/jenkins:lts
        ports:
        - containerPort: 8080
        volumeMounts:
        - name: jenkins-home
          mountPath: /var/jenkins_home
      volumes:
      - name: jenkins-home
        persistentVolumeClaim:
          claimName: jenkins-pvc
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: jenkins-pvc
  namespace: jenkins
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: local-path
  resources:
    requests:
      storage: 10Gi
---
apiVersion: v1
kind: Service
metadata:
  name: jenkins
  namespace: jenkins
spec:
  type: NodePort
  ports:
    - port: 8080
      targetPort: 8080
      nodePort: 30000
  selector:
    app: jenkins
EOF

Pro Tip: I've set the nodePort to 30000, but you can choose any port between 30000-32767. Just make sure it's not being used by other services.

Accessing Jenkins

Once deployed, wait a few minutes for Jenkins to initialize. You can monitor the pod status:

kubectl get pods -n jenkins

To get the initial admin password:

kubectl exec -n jenkins $(kubectl get pods -n jenkins -l app=jenkins -o jsonpath='{.items[0].metadata.name}') -- cat /var/jenkins_home/secrets/initialAdminPassword

Access Jenkins through your browser using:

http://your-server-ip:30000

Troubleshooting Common Issues

During my deployment journey, I encountered a few hiccups. Here's how to resolve them:

Pod Stuck in Pending State

If your Jenkins pod is stuck in pending state, check the events:

kubectl describe pod -n jenkins $(kubectl get pods -n jenkins -l app=jenkins -o jsonpath='{.items[0].metadata.name}')

Common causes include:

Insufficient resources - Adjust the resource requests in the deployment YAML
PVC binding issues - Verify your StorageClass configuration
Node port conflicts - Change the nodePort value in the service configuration

Security Considerations

Before using Jenkins in production, I strongly recommend:

Setting up HTTPS using cert-manager or an ingress controller
Implementing role-based access control (RBAC)
Regularly updating Jenkins and its plugins
Backing up the Jenkins home directory regularly

Have you deployed Jenkins on K3s? I'd love to hear about your experience send me an email.

Remember: Always keep your Jenkins instance updated and secured. The configurations provided here are basic examples and should be enhanced based on your security requirements.