What is Jenkins?
Jenkins is an open-source automation server that helps automate parts of the software development process. It is commonly used for continuous integration and delivery of projects, although it can also be used to automate other tasks. Jenkins provides hundreds of plugins to support building, deploying, and automating any project. Some common use cases for Jenkins include building and testing software projects continuously, running automated tests, deploying software to production, and more
Here are some important topics related to Jenkins:
Jenkins important plugins
Jenkins plugins are add-ons that extend the functionality of Jenkins. There are hundreds of plugins available, which provide integration with a wide range of tools and services. Some common Jenkins plugins include:
These are just a few examples, but there are many more Jenkins plugins available that you can use to customize Jenkins to meet your specific needs.
Jenkins Backup
There are several ways you can back up your Jenkins instance:
It is important to regularly back up your Jenkins instance to protect against data loss. You should determine the best backup strategy for your needs based on your specific requirements and available resources.
Declarative VS Scripted pipeline
In Jenkins, a pipeline is a suite of plugins that supports implementing and integrating continuous delivery pipelines into Jenkins. There are two types of pipelines in Jenkins: Declarative and Scripted.
Declarative Pipeline?is a more recent feature of Jenkins that provides a more simplified and efficient syntax for defining pipelines as code. It is based on a?Domain Specific Language (DSL)?that is written in Groovy and uses a more structured and concise syntax. Declarative pipelines are?easier to read and understand, and they can be more flexible and powerful than traditional scripted pipelines.
Scripted Pipeline?is the older, more traditional way of defining pipelines in Jenkins. It is a more powerful and flexible way of defining pipelines, but it requires you to?write code in the Groovy programming language. Scripted pipelines can be?more complex?to write and maintain than declarative pipelines.
Both Declarative and Scripted pipelines can be used to create Jenkins pipelines, and the choice between the two will depend on your specific needs and preferences.
Declarative Pipeline
In Jenkins, a Declarative Pipeline is a way to define a Jenkins pipeline using a?more structured and simplified syntax. Declarative Pipelines are defined using a?Groovy-based DSL?(Domain Specific Language).
A Declarative Multi-Stage Pipeline is a Declarative Pipeline that is divided into multiple stages. Each stage represents a phase in the delivery pipeline, and it specifies the actions that need to be executed in that phase. For example, a multi-stage pipeline might have stages for building, testing, and deploying a software application.
Here is an example of a Declarative Multi-Stage Pipeline:
pipeline {
agent {
docker {
image 'maven:3.6.3-jdk-11'
args '-v /root/.m2:/root/.m2'
}
}
stages {
stage('Build') {
steps {
sh 'mvn -B -DskipTests clean package'
}
}
stage('Test') {
steps {
sh 'mvn test'
}
}
stage('Deploy') {
steps {
sh './deploy.sh'
}
}
}
}
In this example, the pipeline has three stages: Build, Test, and Deploy. The Build stage runs the Maven clean and package goals, the Test stage runs the Maven test goal, and the Deploy stage runs a script called?deploy.sh.
Scripted Pipeline
In Jenkins, a Scripted Pipeline is a way to define a Jenkins pipeline using the?Groovy programming language. A Scripted Pipeline is typically written in a Jenkinsfile, which is checked into source control.
A Scripted Multi-Stage Pipeline is a Scripted Pipeline that is divided into multiple stages. Each stage represents a phase in the delivery pipeline, and it specifies the actions that need to be executed in that phase. For example, a multi-stage pipeline might have stages for building, testing, and deploying a software application.
Here is an example of a Scripted Multi-Stage Pipeline:
node {
stage('Build') {
sh 'mvn -B -DskipTests clean package'
}
stage('Test') {
sh 'mvn test'
}
stage('Deploy') {
sh './deploy.sh'
}
}
In this example, the pipeline has three stages: Build, Test, and Deploy. The Build stage runs the Maven clean and package goals, the Test stage runs the Maven test goal, and the Deploy stage runs a script called?deploy.sh.
Scripted pipelines offer more flexibility and power than Declarative Pipelines, but they can be more difficult to write and maintain. You should choose the type of pipeline that is best suited to your needs based on your specific requirements and expertise.
Declarative pipeline with an example
This is an example of a Declarative Pipeline that can be used to build, test, and deploy a Java application using Maven, SonarQube, Docker, and Ansible:
pipeline {
agent {
docker {
image 'maven:3.6.3-jdk-11'
args '-v /root/.m2:/root/.m2'
}
}
stages {
stage('Build') {
steps {
sh 'mvn -B -DskipTests clean package'
}
}
stage('Test') {
steps {
sh 'mvn test'
sh 'sonar-scanner'
}
}
stage('Containerize') {
steps {
sh './containerize.sh'
}
}
stage('Deploy') {
steps {
withCredentials([usernamePassword(credentialsId: 'kubernetes-deploy', passwordVariable: 'KUBERNETES_PASSWORD', usernameVariable: 'KUBERNETES_USERNAME')]) {
sh 'ansible-playbook deploy.yml -e "kubernetes_username=${KUBERNETES_USERNAME} kubernetes_password=${KUBERNETES_PASSWORD}"'
}
}
}
}
}
In this example, the pipeline has four stages: Build, Test, Containerize, and Deploy. The Build stage runs the Maven clean and package goals, the Test stage runs the Maven test goal and runs a SonarQube scan, the Containerize stage runs a script called?containarize.sh?to create a Docker container, and the Deploy stage uses Ansible to deploy the container to Kubernetes.
This pipeline assumes that the necessary credentials for deploying to Kubernetes are stored in Jenkins and are configured with the ID kubernetes-deploy. It also assumes that the sonar-scanner command is available on the PATH and that an Ansible playbook called deploy.yml exists in the Jenkins workspace.
Restart Jenkins Server
There are several ways to restart a Jenkins server:
Restart from the Jenkins UI:
Restart from the command line:
Restart from the Jenkins CLI:
It is important to note that restarting the Jenkins server will interrupt any running builds and may cause other disruptions. You should only restart the Jenkins server if it is necessary for maintenance or troubleshooting purposes.
Jenkins Password Reset
If you have forgotten the admin password for your Jenkins instance and you are unable to log in, you can try resetting the password using the following steps:
Check if you have access to the Jenkins server file system:
Reset the password:
It is important to note that resetting the Jenkins admin password will also reset the passwords of any other users who have forgotten their passwords. You should only reset the password if you are unable to log in and you do not have any other options.
Jenkins Job types
Jenkins is an open-source automation tool that allows users to build, test, and deploy software. It supports various job types, including:
These are just a few examples of the many job types available in Jenkins. Depending on the version you are using, you may have access to other job types as well.
Adding Slave node to Jenkins server
To add a slave node to a Jenkins server, you will need to follow these steps:
After saving the configuration, Jenkins will display the command that you need to run on the slave machine to launch the slave agent. You will need to run this command on the slave machine to launch the agent and connect it to the Jenkins server.
It is important to note that the slave node will need to be able to communicate with the Jenkins server over the network in order to be able to connect. You may need to configure your firewall and network settings to allow communication between the slave and the Jenkins server.
Integrate Jenkins with other DevOps tools.
1. To add Git to Jenkins, you will need to follow these steps:
a. Install Git:
b. Install the Git Plugin:
c. Configure Git:
After you have completed these steps, you should be able to use Git in your Jenkins builds. You can specify the Git installation that you configured in the "Global Tool Configuration" page as a build tool in your Jenkins projects.
2. To integrate GitHub with a Jenkins pipeline, you will need to follow these steps:
a. Install the GitHub Plugin:
b. Configure the GitHub Webhook:
c. Create a Jenkins pipeline and add a step to fetch the code from GitHub.
Here is an example of how you can fetch code from GitHub and build it in a Jenkins pipeline:
pipeline {
agent any
stages {
stage('Fetch') {
steps {
git url: 'https://github.com/user/repo.git'
}
}
stage('Build') {
steps {
// Build steps go here
}
}
}
}
In this example, the git step is used to fetch the code from GitHub. The url parameter specifies the URL of the Git repository.
It is important to note that you will need to have the GitHub Plugin installed and the GitHub webhook configured for the pipeline to be triggered when code is pushed to or a pull request is created in the GitHub repository. You can configure the GitHub webhook as described in step 2.
3. To add SonarQube to Jenkins, you will need to follow these steps:
a. Install the SonarQube Plugin:
b. Configure the SonarQube Server:
c. Analyze Your Code:
4. To add Maven to Jenkins, you will need to follow these steps:
a. Install Maven:
b. Install the Maven Plugin:
c. Configure Maven:
5. To add Docker to Jenkins, you will need to follow these steps:
a. Install Docker:
b. Install the Docker Plugin:
c. Configure Docker:
After you have completed these steps, you should be able to use.
6. To use Kubernetes in Jenkins, you will need to follow these steps:
a. Install the Kubernetes Plugin:
b. Configure the Kubernetes Plugin:
After you have completed these steps, you should be able to use Kubernetes in your Jenkins builds. You can use the Kubernetes Plugin to run Jenkins agents in Kubernetes pods and to dynamically provision and manage the resources required for your Jenkins builds.
7. To use Ansible in Jenkins, you will need to follow these steps:
a. Install Ansible:
b. Install the Ansible Plugin:
c. Configure Ansible:
After you have completed these steps, you should be able to use Ansible in your Jenkins builds. You can specify the Ansible installation that you configured in the "Global Tool Configuration" page as a build tool in your Jenkins projects. You can also use the Ansible Plugin to run Ansible playbook tasks as part of your Jenkins builds.
8. To configure email notifications in Jenkins, you will need to follow these steps:
a. Install the Email Extension Plugin:
b. Configure the SMTP Server:
c. Configure the Email Notifications:
Create a Jenkins pipeline and add a step to send an email notification.
Here is an example of how you can send an email notification in a Jenkins pipeline:
pipeline {
agent any
stages {
stage('Build') {
steps {
// Build steps go here
}
}
stage('Notify') {
steps {
script {
// Send an email notification
emailext attachmentsPattern: '**/build.log', body: 'The build has completed. See attached build log for details.', subject: 'Build Results - ${currentBuild.fullDisplayName}', to: '[email protected]'
}
}
}
}
}
In this example, the emailext step is used to send an email notification. The attachmentsPattern parameter specifies the pattern of the files to be attached to the email. The body parameter specifies the content of the email, and the subject parameter specifies the subject of the email. The to parameter specifies the recipients of the email. You can customize the email notification by using variables such as ${currentBuild.fullDisplayName} and ${currentBuild.status} in the subject and body of the mail.