centos jenkins如何使用Docker

Prerequisites
Before using Jenkins with Docker on CentOS, ensure Docker is installed and running. If not, follow these steps:

1. Update system packages: sudo yum update -y.
2. Install Docker dependencies: sudo yum install -y yum-utils device-mapper-persistent-data lvm2.
3. Add Docker’s official repository: sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo.
4. Install Docker CE: sudo yum install -y docker-ce docker-ce-cli containerd.io.
5. Start and enable Docker: sudo systemctl start docker & & sudo systemctl enable docker.

Install Jenkins via Docker
You can install Jenkins in two ways: using the official Jenkins image or a custom CentOS-based image.

Option 1: Use Official Jenkins Image (Recommended)

The official jenkins/jenkins:lts image (LTS = Long-Term Support) is the most stable choice.

1. Pull the Jenkins Image:
   Run docker pull jenkins/jenkins:lts to download the latest LTS version.
2. Run the Jenkins Container:
   Use the following command to start a container with persistent storage (to retain data after restarts) and port mappings:

   docker run -d \
     --name jenkins \
     -p 8080:8080 \          # Map host port 8080 to container's Jenkins web UI
     -p 50000:50000 \        # Map host port 50000 for Jenkins agent communication
     -v jenkins_home:/var/jenkins_home \  # Persistent volume for Jenkins data
     --restart=on-failure \   # Auto-restart container if it fails
     jenkins/jenkins:lts
   

   Key flags:
   • -d: Run in detached mode (background).
   • -v jenkins_home:/var/jenkins_home: Mount a Docker volume to persist Jenkins configurations, jobs, and plugins.
   • --restart=on-failure: Ensures the container restarts automatically if it crashes.

Option 2: Create a Custom CentOS-Based Jenkins Image

If you need a CentOS-specific environment (e.g., for compatibility with existing CentOS-based tools), create a custom image using a Dockerfile:

1. Create a Directory for the Dockerfile:
   mkdir custom-jenkins & & cd custom-jenkins.
2. Write the Dockerfile:
   Create a file named Dockerfile with the following content:

   FROM centos:7
   RUN yum install -y java-1.8.0-openjdk-devel git wget &
       &
        yum clean all
   RUN wget -O /etc/yum.repos.d/jenkins.repo http://pkg.jenkins-ci.org/redhat/jenkins.repo &
       &
        \
       rpm --import https://pkg.jenkins.io/redhat/jenkins.io.key &
       &
        \
       yum install -y jenkins &
       &
        yum clean all
   ENV JENKINS_HOME /var/lib/jenkins
   EXPOSE 8080
   CMD ["/usr/bin/java", "-Djava.awt.headless=true", "-jar", "/usr/lib/jenkins/jenkins.war", "--webroot=/var/cache/jenkins/war", "--httpPort=8080"]
   

   This installs Java (required for Jenkins), Git (for source control), and Jenkins on CentOS 7.
3. Build the Image:
   Run docker build -t custom-jenkins . to create the image.
4. Run the Container:
   Use docker run -d -p 8080:8080 --name jenkins custom-jenkins to start the container.

Initialize Jenkins
After starting the container, complete the initial setup:

1. Get the Initial Admin Password:
   Run docker logs jenkins to view the logs, then copy the auto-generated password (e.g., 447a868d1fd64cbc8dbf66792f31425d).
2. Access the Jenkins Web UI:
   Open a browser and navigate to http://< your_server_ip> :8080. Paste the password into the “Unlock Jenkins” page.
3. Install Recommended Plugins:
   Select “Install suggested plugins” to install essential plugins (e.g., Git, Pipeline, SSH). This may take a few minutes.
4. Create an Admin User:
   Fill in the user details (username, password, full name, email) and click “Save and Finish”.
5. Start Using Jenkins:
   Click “Start using Jenkins” to access the dashboard.

Integrate Jenkins with Docker
To use Docker within Jenkins (e.g., building/publishing Docker images), configure the Docker plugin and connect to the Docker daemon:

1. Install Docker Plugin:
   Go to “Manage Jenkins” > “Manage Plugins” > “Available”. Search for “Docker Pipeline” and install it.
2. Configure Docker Cloud:
   Navigate to “Manage Jenkins” > “Configure System”. Under the “Cloud” section, click “Add a new cloud” > “Docker”.
   • Enter a name (e.g., “Local Docker”).
   • Set “Docker Host URI” to unix:///var/run/docker.sock (default for local Docker).
   • Click “Test Connection” to verify access (should return “Connection successful”).
3. Create a Pipeline Job:
   • Go to “New Item” > enter a job name (e.g., “Docker Build”) > select “Pipeline” > click “OK”.
   • In the pipeline script, add a stage to build a Docker image:

     pipeline {
     
         agent any
         stages {
     
             stage('Build Docker Image') {
     
                 steps {
     
                     script {
     
                         def imageName = "my-app:${
     env.BUILD_ID}
     "
                         docker.build(imageName)
                         echo "Built image: ${
     imageName}
     "
                     }
     
                 }
     
             }
     
         }
     
     }
         
     

   • Save and run the job. The pipeline will build a Docker image tagged with the build ID.

Key Tips for Production Use

• Use Specific Image Tags: Avoid latest (e.g., jenkins/jenkins:lts instead of jenkins/jenkins:latest) for stability.
• Secure Jenkins: Change the default admin password, restrict access via firewall (e.g., allow only internal IPs to port 8080), and consider enabling HTTPS.
• Backup Data: Regularly back up the jenkins_home volume (e.g., docker run --rm -v jenkins_home:/volume -v $(pwd):/backup ubuntu tar cvf /backup/jenkins_backup.tar /volume).
• Resource Limits: Allocate CPU/memory limits to the Jenkins container (e.g., --cpus="2" --memory="4g" in the docker run command) to prevent resource exhaustion.

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