Ubuntu 18.04 LTS安装Jenkins失败：无法启动LSB开机自启服务

Hey there, let's work through this Jenkins startup issue you're facing. That error message is a common one, and it typically stems from a few key problems—let's go through each fix step by step.

1. Verify Java Version Compatibility #

Jenkins 2.107.2 requires Java 8 (either OpenJDK or Oracle JDK) to run properly. If your system has a newer Java version (9+), this will almost certainly cause startup failures.

First, check your current Java version:

java -version

If it's not Java 8, install OpenJDK 8:

sudo apt install openjdk-8-jre-headless

Then set Java 8 as your default version:

sudo update-alternatives --config java

Select the option corresponding to OpenJDK 8 when prompted.

2. Check for Port Conflicts #

Jenkins uses port 8080 by default. If another application is hogging this port, Jenkins won't be able to start up.

Check if port 8080 is occupied:

sudo lsof -i :8080
# Or alternatively:
sudo netstat -tulpn | grep 8080

If you see a process using the port, you have two options:

• Kill the conflicting process (replace <PID> with the process ID from the output):

  sudo kill -9 <PID>
  

• Change Jenkins' default port:
  Edit the Jenkins config file:

  sudo nano /etc/default/jenkins
  

  Find the line HTTP_PORT=8080 and change it to a free port (e.g., HTTP_PORT=8081). Save the file, then restart Jenkins:

  sudo systemctl restart jenkins
  

3. Inspect Jenkins Logs & Fix Permissions #

Detailed logs will often tell you exactly what's going wrong. Let's check two key log sources:

Systemd Service Logs #

sudo journalctl -u jenkins

Jenkins Application Logs #

tail -n 50 /var/log/jenkins/jenkins.log

If you see permission errors (e.g., "Permission denied" when writing to logs or directories), fix the ownership and permissions:

sudo chown -R jenkins:jenkins /var/log/jenkins
sudo chmod -R 755 /var/log/jenkins

4. Refresh Systemd Configuration #

Sometimes the systemd service definition can get messed up during installation. Refresh it and re-enable the service:

sudo systemctl daemon-reload
sudo systemctl enable jenkins
sudo systemctl start jenkins

After trying these steps, check if Jenkins is running with:

sudo systemctl status jenkins

内容的提问来源于stack exchange，提问作者Gaspar Cheng