Continuous Deployment to Kubernetes with Dynamic Jenkins Slave and Docker

Fasten your safety belt, and departing …..

1. Create a pipeline job.
2. Setup your SCM and build from Jenkinsfile (sample provided below).

//Sample Jenkinsfile 

def AGENT_LABEL = "slave-${UUID.randomUUID().toString()}"
def K8S_DEPLOYMENT_FILE = "k8s-service.yml"

// This is where the dynamic slave magic happen, 
// it launch the agent using randomly generated number as k8s pod 
pipeline {
    agent {
        kubernetes {
            label "${AGENT_LABEL}"
            defaultContainer 'jenkins-jnlp-slave-docker'
            yamlFile 'k8s-jnlp-slave.yml'

    stages {
        stage('Build artifacts') {
            steps {
                // maven3 need to pre-configure in Jenkins
                // mavenSettingsConfig is optional when you have customize settings.xml file using Config File Management plugin
                withMaven(maven: 'maven3', mavenSettingsConfig: 'maven-settings') {                    
                    sh "mvn clean install -Dmaven.test.skip=true"

        stage('Build Docker Image') {
            steps {
                script {
                    withEnv(["WORKSPACE=${pwd()}"]) {                                            
                        //docker-credential is credential set in Jenkins to authenticate against your docker registry
                        docker.withRegistry("YOUR_NEXUS_REGISTRY", 'docker-credential') {
                            def image ="YOUR_IMAGE_NAME", "PROJECT_DIR/Dockerfile .")   

        stage('Run kubernetes deployment') {
            steps {                
                // kubeconfig is your kube config file which need to pre-configure in Jenkins as secret file
                // check step 5 below
                withKubeConfig([credentialsId: 'kubeconfig']) {                    
                    sh "kubectl create -f ${K8S_DEPLOYMENT_FILE}"                    
#Sample k8s-jnlp-slave.yml

apiVersion: v1
kind: Pod
    name: jenkins-jnlp-slave-docker
  - name: jenkins-jnlp-slave-docker
    image: d1ck50n/jenkins-jnlp-slave-docker:latest
    command: ['cat']
    tty: true
    imagePullPolicy: Always    
    - name: dockersock
      mountPath: "/var/run/docker.sock"
  - name: tntcred
  - name: dockersock
      path: /var/run/docker.sock

Jenkins slave is docker, and we will use it to build our docker images, which means we will need to have a docker engine inside Jenkins slave docker (a.k.a docker in docker). Since I’m not able to make use of ready made docker image available @ docker hub as my jenkins slave (I need jdk, maven, kubectl… too as my jenkins slave) , so I created my own based on jenkins/jnlp-slave image.
To achieve DoD, we map the docker.sock from the host to our container (‘dockersock’ in k8s-jnlp-slave.yml).

3. Install plugins as below:
4.Create jenkins kubernetes plugin by adding new entry.

5. Fill in configuration according to your kubernetes cluster or use your kube config file by adding credential as highlighted below:

6. Regardless you configure manually or using your customize kube config file, you need to test the connection.
7. Build your job and you should see a new node created and start building.
Source available @ github.

Credits to authors and websites below:


Docker: exec user process caused “no such file or directory”

Have no idea why Docker showing this (un-friendly) error message.
In fact, it caused by the bash script file created in Windows having different line ending and cannot run properly in Linux container.

standard_init_linux.go:190: exec user process caused "no such file or directory"

Here is the fix using Notepad++.
First show the linefeed symbol.

You will see this.

Convert the linefeed from Windows to Unix.

You will get this, and save it 🙂


3 minutes Docker Introduction


Many years ago, what we do when we want to deploy and run our application after development? Typically we will setup physical machine, this normally including but not limited to system tools, jdk, python, database, application server etc..etc.. then deploy and run.

If we have multiple environment to deploy and run, then we repeat the same step for all environment, eg: dev, qa, staging, production.

After few years, people tend to make their life easier by not setup, deploy and run the application directly on physical machine, but using virtual machine where they can easily clone it for other environment (figure 1 show architecture of virtual machine).

docker1figure 1
image from:

When more and more application run with different runtime environment, framework version, database vendor, server etc… Of cause deploying and running on top of virtual machine still works fine, but virtual machine is an operating system imitates dedicated hardware, meaning it shared host hardware system’s resources, which will then no longer available to the hosted applications.

Emerged of Docker container in perfect timing is good fit for this. It is a process that talks directly to the Linux kernel. And run as isolated process in host operating system. Meaning, we can now deploy our application in smaller container instead of virtual machine. (figure 2 show architecture of Docker).

docker2figure 2
image from:

If you still confuse Docker is just another type of virtual machine, figure 3 might clear your doubts.

figure 3

p/s: Docker looks promising and it is really a good match for microservices, nevertheless, it has some security concern as they are sharing same kernel with host.
Container and virtual machine have different strength, hence should not viewed as competitors, but complimentary.

Docker documentation
Self-pace video tutorial
Virtualization vs. Containers: What You Need to Know