All-Things-Docker-and-Kubernetes

Lab 010: Running a Jenkins Container

• Pre-requisites
• Introduction
• Docker run
• Cleanup

Pre-requisites

• Install Docker

Introduction

In this lab, we’ll mix up the Docker concepts we’ve played around so far. This is a fairly simple lab as no dockerfile is required and the official container image is already available.

Docker run

We will spin up a Jenkins container with a specified name and mapped ports. We’ll only use a single docker run commmand:

$ docker run -d --name my-jenkins-svr -u root -p 81:8080 -v /root/new-folder:/var/jenkins_home jenkins/jenkins 

Here’s the breakdown:

• This pull is optional as the run command will automtically pull down the Jenkins image from Dockerhub. Note that you’ll come across the first deprecated version. You’ll have to pull the new one - jenkins/jenkins

  docker pull jenkins/jenkins
  

  docker run jenkins/jenkins 
  

• Specifies a name for our container

  --name my-jenkins-svr
  

• Maps a port using the “-p” flag (8080 is the default port of container, and 81 is a port in our local machine)

  -p 81:8080
  

• Maps the default jenkins directory (that will be created in the container) to a directory in our linux machine by using the “-v” flag

  -v /root/new-folder:/var/jenkins_home
  

• We might encounter a permission error when we try to run the container with the flags. Use the “-u” flag, followed by the user in our linux machine

  -u root
  

  Notice that we use a “-d” flag which means the container will run in the background. To check if the container is running,

$ docker ps

CONTAINER ID   IMAGE             COMMAND                  CREATED         STATUS         PORTS
                    NAMES
fb5f7a292cf9   jenkins/jenkins   "/usr/bin/tini -- /u…"   3 seconds ago   Up 2 seconds   50000/tcp, 0.0.0.0:81->8080/tcp, :::81->8080/tcp   my-jenkins-svr 

Open a web browser and navigate to the IP address of your local machine followed by port 81, like this:

54.151.154.238:81/ 

You should see the “Unlock Jenkins” page. Before we can use Jenkins, we would need to get the password from the terminal first.

Back in our terminal, use the exec instruction to cat the file specified. Notice that we don’t need to specify the entire container ID and just the first three since no other container IDs have the same first three containers, in fact there are no other containers running.

$ docker ps
CONTAINER ID   IMAGE             COMMAND                  CREATED         STATUS         PORTS
                    NAMES
fb5f7a292cf9   jenkins/jenkins   "/usr/bin/tini -- /u…"   3 minutes ago   Up 3 minutes   50000/tcp, 0.0.0.0:81->8080/tcp, :::81->8080/tcp   my-jenkins-svr 

$ docker exec -it fb5 cat /var/jenkins_home/secrets/initialAdminPassword

a1abcdefghijklmnop123456789qrst

Paste the password to the “Unlock Jenkins” page. It should succeed and you should now see the “Customize Jenkins” page.

We’ve successfully deployed a Jenkins container and we’ve verified that it is running by accessing the Jenkins UI console. We’ll end this lab here for now but we’ll have an entire set of labs for Jenkins in another repository which I will link here soon.

Cleanup

When you’re done with the lab, you can stop all running containers by running the command below.

$ docker stop $(docker ps) 

Once all containers have “Exited” status, remove them.

$ docker ps  -a 

$ docker container prune -f 

Finally, remove all images.

$ docker image prune -af 

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