Installation

Installation on Fedora:

$ sudo dnf install jenkins

Run in a container - this will make Jenkins available at http://localhost:49001:

$ podman run --rm --name jenkins -d -p 49001:8080 jenkins/jenkins:lts

Pipelines

  • Declarative Pipelines are a more simplified and opinionated syntax on top of the Pipeline sub-system.

Example - declarative pipeline using OpenShift/Kubernetes pods

pipeline {
    agent {
      label "master"
    }
    stages {
        stage('build') {
            steps {
                sh 'echo HEY YALL'
            }
        }
    }
}

Pipeline cookbook

Cloning a Git repository at a specific tag

Due to JENKINS-27018, you can’t check out a tag using the git step. You need to use the checkout step, e.g.:

checkout([
    $class: 'GitSCM',
    branches: [[name: 'refs/tags/my-tag-name']],
    userRemoteConfigs: [[
        credentialsId: 'my-git-credentials-id',
        url: 'https://gitlab.examplecat.com/team/my-repo.git'
    ]]
])

Store the contents of a file in a variable

script {
    env.SOME_FILE_CONTENT="cat path/to/some_file.txt".execute().text
}

Starting a job

To run another Jenkins build job from your pipeline:

build job: 'my-job-name',
      parameters: [[$class: 'StringParameterValue', name: 'APP_NAME', value: "${APP_NAME}" ],
                   [$class: 'StringParameterValue', name: 'PORT', value: "8080" ]],
      wait: false

Curl a list of URLs with variable expansion

withCredentials([usernamePassword(credentialsId: 'my-credentials', usernameVariable: 'GIT_USER', passwordVariable: 'GIT_PASS')]) {
  sh 'while read -r line; do eval curl -s -k "\$line" -u $GIT_USER:$GIT_PASS; done < urls.txt'
}

Waiting for a StatefulSet to become ready

Grant Jenkins permissions to view objects in the namespace:

oc policy add-role-to-user view -z jenkins

Then:

pipeline {
  agent {
    label "master"
  }
  stages {
    stage('deploy statefulset') {
      steps {
        sh 'echo WELCOME TO MY PIPELINE YALL'

        // DO SOMETHING here to create the StatefulSet first...

        script {
          openshift.withCluster() {
            openshift.withProject("tad-cicd") {
              echo 'Checking StatefulSet pods are all ready...'
              def sts = openshift.selector("sts", "sleepy-python")

              // If the time limit is reached, the build will be aborted with a FlowInterruptedException
              timeout (time: 5, unit: 'MINUTES') {
                sts.untilEach(1){
                  def stsMap = it.object()
                  return (stsMap.status.replicas.equals(stsMap.status.readyReplicas))
                }
              }

              echo 'We think the StatefulSet is now ready!'
            }
          }
        }
      }
    }
  }
}

Shared libraries

Fetching a shared library from a private repo. Firstly add credentials into Jenkins, and then:

library identifier: 'mylibraryname@master', //'master' refers to a valid git-ref
retriever: modernSCM([
  $class: 'GitSCMSource',
  credentialsId: 'your-credentials-id',
  remote: 'https://github.com/monodot/private-jenkins-library.git'
])

pipeline {
    agent any
    stages {
        stage('Demo') {
            steps {
                echo 'Hello world'
                sayHello 'Dave'
            }
        }
    }
}

REST API

To use the Jenkins REST API, you’ll first need the user’s API token:

  1. Go to the user Configure page ($JENKINS_URL/user/$USER/configure)
  2. Click the button to get your API Token.

Then you can access the API using curl.

API Cookbook

The following examples expect these environment variables to be set:

export JENKINS_URL=http://myjenkins.example.com
export JENKINS_USER=myusername
export JENKINS_TOKEN=xyzyxzyxzyxzyzy
export JENKINS_FOLDER=foldername
export JENKINS_JOB_NAME=myjobname

Get a crumb token (if Cross Site Request Forgery protection is enabled):

$ curl -s --user $JENKINS_USER:$JENKINS_PASSWORD $JENKINS_URL/crumbIssuer/api/json
{"_class":"hudson.security.csrf.DefaultCrumbIssuer","crumb":"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa","crumbRequestField":"Jenkins-Crumb"}
$ export JENKINS_CRUMB=$(curl -s --user $JENKINS_USER:$JENKINS_PASSWORD $JENKINS_URL/crumbIssuer/api/json | jq -r '.crumb')

Start a job using default parameters (these don’t work….yet):

$ curl -X POST $JENKINS_URL/job/$JENKINS_FOLDER/job/$JENKINS_JOB_NAME/build \
    -H Jenkins-Crumb:$JENKINS_CRUMB \
    --user $JENKINS_USER:$JENKINS_TOKEN

$ curl -X POST -H Jenkins-Crumb:$JENKINS_CRUMB \
    $JENKINS_URL/job/$JENKINS_FOLDER/job/$JENKINS_JOB_NAME/build?token=$JENKINS_TOKEN

Troubleshooting

“java.io.IOException: Failed to dynamically deploy this plugin” when starting up Jenkins:

  • This may be caused by Jenkins failing to install one of the plugin’s dependencies.
  • Check the first occurrence of this error in the logs.
  • e.g. “SSH Credentials Plugin v1.16 failed to load. You must update Jenkins from v2.60.3 to v2.73.3 or later to run this plugin” => update Jenkins.