# Jenkins on RHEL 9

Login to the node in root and perform the following steps.

Its always better to use the dnf than yum.

> `dnf` is the recommended package manager for Red Hat-based distributions because it offers improved performance, dependency handling, user experience, and compatibility with modern software management practices. While you might still encounter `yum` on older systems or in legacy documentation, it's advisable to use `dnf` for package management on newer distributions.

```bash
sudo dnf update -y
```

In order to run Jenkins, we need to have Java installed on the node.

## Install Temurin JDK

```bash
cat <<EOF > /etc/yum.repos.d/adoptium.repo
[Adoptium]
name=Adoptium
baseurl=https://packages.adoptium.net/artifactory/rpm/${DISTRIBUTION_NAME:-$(. /etc/os-release; echo $ID)}/\$releasever/\$basearch
enabled=1
gpgcheck=1
gpgkey=https://packages.adoptium.net/artifactory/api/gpg/key/public
EOF
```

Install Temurin 11

```bash
dnf -y install temurin-11-jdk
```

## Install Jenkins

Lets add the Jenkins RPM repository!

* Create RPM repository
    
    * ```bash
          wget -O /etc/yum.repos.d/jenkins.repo <https://pkg.jenkins.io/redhat-stable/jenkins.repo>
        ```
        
* Add repository key
    
    * ```bash
          rpm --import <https://pkg.jenkins.io/redhat-stable/jenkins.io.key>
        ```
        
* Add repository key
    
    * ```bash
              rpm --import <https://pkg.jenkins.io/redhat-stable/jenkins.io.key>
        ```
        
* Install Jenkins
    
    * ```bash
             dnf -y install jenkins
        ```
        

## Configure Jenkins

```bash
systemctl --full status jenkins
systemctl edit jenkins
```

* lets add the service with the timezone
    
* ```bash
      [Service]
      Environment="JAVA_OPTS=-Djava.awt.headless=true -Djava.net.preferIPv4Stack=true -Djava.io.tmpdir=/var/cache/jenkins/tmp/ -Dorg.apache.commons.jelly.tags.fmt.timeZone=Asia/Kolkata -Duser.timezone=Asia/Kolkata"
      Environment="JENKINS_OPTS=--pluginroot=/var/cache/jenkins/plugins"
    ```
    
* lets create a tmp directory so that all the created tmp directories will reside here rather than having a pile of everything at one place
    
* ```bash
      mkdir -p /var/cache/jenkins/tmp`
      chown -R jenkins:jenkins /var/cache/jenkins/tmp`
    ```
    
* check if Jenkins is running or not
    
* ```bash
          systemctl show jenkins
    ```
    
* check the service
    
* ```bash
          systemctl show jenkins
    ```
    
* verify and start the Jenkins
    
* ```bash
          systemd-analyze verify jenkins.service
          systemctl start jenkins
          systemctl --full status jenkins
    ```
    
* Check the auto-generated admin password
    
* ```bash
          journalctl -u jenkins
    ```
    
* and add the jenkins service
    
* ```bash
          systemctl enable jenkins
    ```
    
* lets make sure that the firewall does not stop us from viewing the jenkins dashboard
    
* ```bash
      sudo firewall-cmd --zone=public --add-port=8080/tcp --permanent
      sudo firewall-cmd --zone=public --add-port=8443/tcp --permanent
      sudo firewall-cmd --reload
    ```
    
* and if you are using cloud services make sure to add an inbound NSG rule for 8080