How to uninstall Jenkins in RHEL?

To uninstall Jenkins on Red Hat Enterprise Linux (RHEL), you need to systematically stop its services, remove its associated files and directories, and then uninstall the Jenkins package itself. This process ensures a clean removal of the application and its data.

How to Uninstall Jenkins in RHEL?

Uninstalling Jenkins in RHEL involves a few critical steps: stopping the running service, removing configuration and data files, and finally, uninstalling the core package.

Prerequisites

Before you begin, ensure you have sudo privileges or are logged in as the root user to execute system-level commands.

Step-by-Step Uninstallation Process

Follow these steps for a complete removal of Jenkins from your RHEL system:

1. Stop Jenkins Services

The first crucial step is to stop any running Jenkins processes to prevent data corruption and allow files to be removed.

Open your terminal.
Execute the following command to stop the Jenkins service:
```
sudo systemctl stop jenkins
```
To ensure the service is disabled from starting automatically on boot, run:
```
sudo systemctl disable jenkins
```
You can verify the service status using:
```
sudo systemctl status jenkins
```
It should show "inactive (dead)".

2. Remove Jenkins Files and Directories

Jenkins creates various files and directories for its data, configurations, logs, and more. These need to be manually removed for a clean uninstallation.

Jenkins Home Directory: This directory contains all your Jenkins configurations, build history, plugins, and workspace data.
- The default location is /var/lib/jenkins.
- To remove it, use:
```
sudo rm -rf /var/lib/jenkins
```
Jenkins Log Files: Logs are typically stored in a separate directory.
- The default location is /var/log/jenkins.
- To remove it, use:
```
sudo rm -rf /var/log/jenkins
```
Jenkins Configuration Files: System-wide configuration files for Jenkins are usually found here.
- The default location is /etc/sysconfig/jenkins.
- To remove it, use:
```
sudo rm -f /etc/sysconfig/jenkins
```
Other Potential Files: Depending on your setup, you might find a Jenkins WAR file (if installed manually) or other related files. If you installed from a .war file, locate and remove that file as well.

3. Uninstall Jenkins Package

After stopping the service and cleaning up files, the next step is to remove the Jenkins RPM package installed on your system. RHEL uses yum or dnf as its package manager.

To uninstall the Jenkins package, use the following command:

sudo yum remove jenkins
# OR if you are using dnf
sudo dnf remove jenkins

Confirm the removal when prompted.

4. Clean Up Remaining Dependencies (Optional but Recommended)

Sometimes, uninstalling a package might leave behind dependencies that are no longer needed by any other installed software. These are known as orphaned packages.

To remove these orphaned dependencies, you can use the autoremove command:
```
sudo yum autoremove
# OR
sudo dnf autoremove
```

Verifying Uninstallation

To confirm that Jenkins has been completely removed, you can try the following:

Check for the Jenkins package:

sudo yum list installed | grep jenkins
# OR
sudo dnf list installed | grep jenkins

This command should not return any results.

Check for Jenkins service:
```
sudo systemctl status jenkins
```
This should report that the service could not be found or is inactive.
Verify directory removal:
- ls /var/lib/jenkins
- ls /var/log/jenkins
- ls /etc/sysconfig/jenkins
These commands should indicate that the directories or files do not exist.

Summary of Key Commands

Action	Command (Yum/DNF)	Description
Stop Service	`sudo systemctl stop jenkins`	Halts the running Jenkins service.
Disable Service	`sudo systemctl disable jenkins`	Prevents Jenkins from starting on boot.
Remove Data Directory	`sudo rm -rf /var/lib/jenkins`	Deletes all Jenkins data, configurations, etc.
Remove Log Directory	`sudo rm -rf /var/log/jenkins`	Clears all Jenkins log files.
Remove Config File	`sudo rm -f /etc/sysconfig/jenkins`	Deletes the Jenkins system configuration file.
Uninstall Package	`sudo yum remove jenkins` or `sudo dnf remove jenkins`	Uninstalls the Jenkins RPM package.
Remove Orphaned Deps	`sudo yum autoremove` or `sudo dnf autoremove`	Cleans up unneeded dependencies.

For more information on yum or dnf package management, you can refer to the Red Hat documentation.