Manually Restarting Jenkins: A Comprehensive Tutorial

Introduction

Jenkins is a powerful automation server used to implement continuous integration and continuous delivery (CI/CD) workflows. As you install new plugins or make configuration changes, restarting Jenkins can be necessary for these updates to take effect. However, sometimes automatic restarts may fail, necessitating a manual intervention. This tutorial will guide you through various methods to manually restart Jenkins across different operating systems, ensuring smooth operation and up-to-date functionality.

Restarting Jenkins on Different Platforms

1. Using Built-in Web URLs for Safe or Forced Restarts

Jenkins provides built-in web-based options to initiate a restart:

Safe Restart:
- Access URL: http://<jenkins_url>/safeRestart
- This option waits until all running jobs are completed before restarting Jenkins. Any new jobs will be queued and executed post-restart.
Forced Restart:
- Access URL: http://<jenkins_url>/restart
- This command restarts Jenkins immediately, without waiting for current builds to finish.

2. Command Line Methods

Linux Systems

Depending on how Jenkins is installed (via package manager or as a standalone application), the restart process varies slightly:

Using Systemd (Modern Debian-based systems):
```
sudo systemctl restart jenkins
```
Using Service Command:
- For RPM-based distributions like Red Hat:
```
sudo service jenkins restart
```
- For DEB-based distributions:
```
sudo /etc/init.d/jenkins restart
```

These commands are straightforward and allow you to manage Jenkins as a system service.

Windows Systems

For users on Windows, Jenkins can be managed directly through the command line interface:

Stop Jenkins:
- Navigate to your Jenkins installation directory and execute:
```
jenkins.exe stop
```
Start Jenkins:
- Use the following command to start Jenkins:
```
jenkins.exe start
```
Restart Jenkins:
- Simply use:
```
jenkins.exe restart
```

3. Using the Safe Restart Plugin

For an enhanced user experience, consider installing the SafeRestart Plugin. This plugin allows you to perform a safe restart directly from the Jenkins main menu, providing additional convenience and safety by ensuring that all running jobs are completed before restarting.

Best Practices

Backup Configuration: Before performing any major changes or restarts, ensure your Jenkins configuration is backed up.
Monitor Logs: After a restart, check Jenkins logs for any errors or warnings to confirm a successful operation.
Plan Restarts: Schedule restarts during off-peak hours if possible to minimize disruption.

Conclusion

Restarting Jenkins manually can be achieved through several methods depending on your operating system and installation type. Whether you prefer using web-based commands, command-line tools, or the Safe Restart Plugin, understanding these processes ensures that you maintain a robust CI/CD environment with Jenkins. By following this guide, you’ll be well-equipped to manage restarts effectively.