How to Run Jenkins Container as Systemd Service with Docker

Repetitive tasks are usually tedious and end up taking up a lot of your time and energy. Over time, multiple automation tools have been developed to help alleviate the hassle of executing repetitive jobs. One such automation tool is Jenkins. Jenkins is an opensource automation server that is designed to help software developers build, test and deploy applications and thereby streamline the continuous integration and delivery process.

We have penned an article before on how to install Jenkins on CentOS 8/ RHEL 8. In this article, we will do things a little different and run the Jenkins container as systemd service with docker.

Prerequisites

A few things are required before you continue.

Docker installed on your Linux system.
A regular user with sudo privileges.

Step 1) Install Docker Engine

To begin, you need to have Docker engine installed on your system. We have a detailed article on how to install Docker on CentOS 8 / RHEL 8. Run below docker command to display the docker version

$ sudo docker version

From the snippet above, we have confirmed that docker is installed and that we are running docker version 19.03.13.

Step 2) Create a Jenkins user

Next, we will create a ‘Jenkins’ system user that will manage Jenkins service. But first, create a system group for Jenkins:

$ sudo groupadd --system jenkins

Then create Jenkins system user

$ sudo useradd -s /sbin/nologin --system -g jenkins jenkins

And finally add Jenkins user to docker group as shown:

$ sudo usermod -aG docker jenkins

To confirm that Jenkins user is added to the docker group, run the id command as shown

$ id jenkins

Output will be,

[linuxtechi@centos8 ~]$ id jenkins
uid=991(jenkins) gid=986(jenkins) groups=986(jenkins),989(docker)
[linuxtechi@centos8 ~]$

Fantastic! Let’s proceed and pull a Jenkins image.

Step 3) Pull Jenkins Image from Docker hub

Invoke the following command to pull the latest Jenkins image from Docker hub.

$ sudo docker pull jenkins/jenkins:lts

This usually takes a few seconds on a fairly stable internet connection. Once downloaded, verify that the Jenkins image is present by invoking the following command:

$ sudo docker images | grep jenkins

Output of above command would be:

[linuxtechi@centos8 ~]$ sudo docker images | grep jenkins
jenkins/jenkins     lts                 f669140ba6ec        6 days ago          711MB
[linuxtechi@centos8 ~]$

Jenkins requires a persistent storage to store data and re-use even in the event of a container crash. Therefore, we will create a storage directory as shown.

$ sudo mkdir /var/jenkins
$ sudo chown -R 1000:1000 /var/jenkins

Step 4) Create a systemd service for Jenkins

Using your preferred text editor, create a Jenkins systemd file as shown:

$ sudo vi /etc/systemd/system/jenkins-docker.service

Paste the following contents & save the file.

[Unit]
Description=Jenkins Server
Documentation=https://jenkins.io/doc/
After=docker.service
Requires=docker.service

[Service]
Type=simple
User=jenkins
Group=jenkins
TimeoutStartSec=0
Restart=on-failure
RestartSec=30s
ExecStartPre=-/usr/bin/docker kill jenkins-server
ExecStartPre=-/usr/bin/docker rm jenkins-server
ExecStartPre=/usr/bin/docker pull jenkins/jenkins:lts
ExecStart=/usr/bin/docker run  --name jenkins-server  --publish 8080:8080 --publish 50000:50000  --volume /var/jenkins:/var/jenkins_home  jenkins/jenkins:lts
SyslogIdentifier=jenkins
ExecStop=/usr/bin/docker stop jenkins-server

[Install]
WantedBy=multi-user.target

To start Jenkins service, reload systemd first and thereafter start Jenkins.

$ sudo systemctl daemon-reload
$ sudo systemctl start jenkins-docker

Let’s now check if Jenkins is running. To do so, we will execute:

$ sudo systemctl status jenkins-docker

Great ! Jenkins is up and running as a systemd service. Since Jenkins will be running on port 8080, open the port on the firewall as shown:

$ sudo firewall-cmd --permanent --add-port=8080/tcp
$ sudo firewall-cmd --reload

To set up Jenkins, simply browse the server’s URL as shown

http://server-ip:8080

You will get the ‘Unlock Jenkins’ page as shown. To proceed, you need to provide the password that is located in the file shown

[linuxtechi@centos8 ~]$ cat /var/jenkins/secrets/initialAdminPassword
9c61bd823a404056bf0a408f4622aafc
[linuxtechi@centos8 ~]$

Once done, Click on ‘Continue’

Next, select ‘Install suggested plugins’ option as shown.

Thereafter, create an administrative user for the Jenkins account and click ‘Save and continue’

The installer will guide you through the remaining steps right to the very end. After successfull Installation, we will get the following Jenkins dashboard