Jenkins cheatsheet

Service and access

Check	Description
`systemctl status jenkins`	Service status (package install)
`ss -tlnp \| grep 8080`	Default HTTP port
`echo $JENKINS_HOME`	Data directory
`cat /var/lib/jenkins/secrets/initialAdminPassword`	First-time admin password

CLI (jenkins-cli.jar)

wget -q $JENKINS_URL/jnlpJars/jenkins-cli.jar
java -jar jenkins-cli.jar -s $JENKINS_URL -auth user:token help
java -jar jenkins-cli.jar -s $JENKINS_URL list-jobs
java -jar jenkins-cli.jar -s $JENKINS_URL build JOB_NAME -s -v

Pipeline Jenkinsfile snippets

pipeline {
  agent { label 'docker' }
  environment {
    REGISTRY = 'harbor.example.com/project'
  }
  stages {
    stage('Checkout') {
      steps { checkout scm }
    }
    stage('Build image') {
      steps {
        sh 'docker build -t $REGISTRY/app:$BUILD_NUMBER .'
      }
    }
    stage('Push') {
      steps {
        withCredentials([usernamePassword(credentialsId: 'harbor', usernameVariable: 'U', passwordVariable: 'P')]) {
          sh 'echo $P | docker login $REGISTRY -u $U --password-stdin'
          sh 'docker push $REGISTRY/app:$BUILD_NUMBER'
        }
      }
    }
  }
}

Useful Groovy / steps

Snippet	Description
`sh 'command'`	Run shell on agent
`checkout scm`	Clone configured SCM
`withCredentials([...]) { }`	Inject secrets
`when { branch 'main' }`	Conditional stage
`parallel { ... }`	Concurrent stages
`timeout(time: 30, unit: 'MINUTES')`	Stage timeout

Agent and executor checks

# UI: Manage Jenkins → Nodes
# CLI:
java -jar jenkins-cli.jar -s $JENKINS_URL list-nodes
java -jar jenkins-cli.jar -s $JENKINS_URL get-node AGENT_NAME

Logs and disk

Path / command	Description
`tail -f /var/log/jenkins/jenkins.log`	Server log (Debian)
`journalctl -u jenkins -f`	systemd journal
`du -sh $JENKINS_HOME/workspace/*`	Workspace disk use
Build → Console Output	Per-build log in UI

Safe restart

# UI: Manage Jenkins → Prepare for Shutdown / Restart
java -jar jenkins-cli.jar -s $JENKINS_URL safe-restart
# Or: systemctl restart jenkins (running builds may abort)

Pro tips

Console Output is the first log to read on any failed build
Pin plugins — document versions before upgrading Jenkins LTS
Use labels (agent { label 'linux' }) to target the right executors
Clean old builds and workspaces — disk fills silently under JENKINS_HOME
Store secrets in Credentials, not in the Jenkinsfile in Git

Practice scenarios

Hands-on Jenkins scenarios on live Linux VMs: jenkins