Jenkins Setup - Install Java , Jenkins Slave machine on Ubuntu EC2 Instance

Basic information about Jenkins Master and Slave
Jenkins Master

Your main Jenkins server is the Master. The Master’s job is to handle:

• Scheduling build jobs.
• Dispatching builds to the slaves for the actual execution.
• Monitor the slaves (possibly taking them online and offline as required).
• Recording and presenting the build results.
• A Master instance of Jenkins can also execute build jobs directly.

Jenkins Slave

A Slave is a Java executable that runs on a remote machine. Following are the characteristics of Jenkins Slaves:

• It hears requests from the Jenkins Master instance.
• Slaves can run on a variety of operating systems.
• The job of a Slave is to do as they are told to, which involves executing build jobs dispatched by the Master.
• You can configure a project to always run on a particular Slave machine, or a particular type of Slave machine, or simply let Jenkins pick the next available Slave.

Let's see how to configure both Jenkins master and slave nodes on Ubuntu EC2.

Jenkins Master Creation link: How to Create Jenkins Master

Step 1 : Create another Jenkins Slave machine instance in AWS EC2 

Create another user in the Jenkins Slave machine as Jenkins-slave and follow the below commands
Step 2 - $ sudo su
Step 3 -  sudo adduser --home /home/jenkins-slave --shell /bin/bash --ingroup admin jenkins-slave


Logged into  created user using
Step 4 - $ sudo su - jenkins-slave

Step 5 : Now type  ssh-keygen (and then simply enter four times, do not give any password)

Set no password authentication  in /etc/sudoers
Step 6 - vi /etc/sudoers and type the following command in the sudoers file, hit the "Esc" key from keyboard and save the file by typing "wq!"

Step 7 : Copy the "Private key (id_rsa)" from ~/.ssh/id_rsa file by typing below commad

         cat ~/.ssh/id_rsa  or Go To ---> .ssh folder "cd .ssh"
         

Step 8 : Go to Master Jenkins and type the jenkins URL like "http://3.19.211.7:8080/"

Step 9 : Add SSH Keys from Master to Slave

Execute the below command in Jenkins master Ec2.
sudo cat ~/.ssh/id_rsa.pub

Copy the output of the above command:

Step 10 : Now go to Slave node and execute the below command and paste the "id_rsa.pub" key to authorized_keys

jenkins-slave@ip-172-31-33-151:~/.ssh$ vi authorized_keys

Once you pasted the public keys in the above file in Slave, come out of the file by entering wq! and enter again

Now go into master node
ubuntu@ip-172-31-41-76:~$ sudo ssh jenkins-slave@172.31.33.151

this is to make sure the master is able to connect the slave node. once you are successfully logged into the slave, type exit to come out of the slave.

And type the below commands 

Step # Register slave node in Jenkins:
Now to go Jenkins Master, manage jenkins, manage nodes.

1. Click on new node. 
2. give the name and check permanent agent, 
3. give a name and no of executors as 1 or 2 or based on your requirement. 
4. enter /home/Jenkins-slave as a remote directory.
5. select launch method as Launch slaves nodes via SSH.
6. enter Slave node private ip address as Host.

       7. Click on [Add] and click on [Jenkins] it will redirect to another window

        8.  Select the "SSH Username with Private Key" and fill the necessary information as below image

   

    9. type the command cat ~/.ssh/id_rsa  looks like the below image (text hidden in the image) 
    (Make sure you copy the whole key including the below without missing anything)
-----BEGIN RSA PRIVATE KEY-----

-----END RSA PRIVATE KEY----


 10 . Paste in the "Private key" in the text area as mentioned in below image

11. After that Select the "Username" from [Credentials] drop-down list as shown in below image and click on [SAVE] button.

Step # : Create a new Jenkins Job in Jenkins Master 

Step #: Type Project Name and Project Type  and click on the [OK] button

Step #: Go To -> General tab and check the [Restrict where this project can be run] and enter the slave machine name

Step #: Click on "Build Environment" and select Build type as "Execute Shell" and click on [save] button by typing some as like in below 

Step #: Go To Jenkins Dashboard and click on [Build Now] to run the job and check the output

Step #: Go to Jenkins Slave Machine and type the below commands 

             sudo su - jenkins-slave and press "ls"

 Type "cd workspace" and press "ls"  select desired  like "Jenkins-Slave-job" and press "ls" again to verify the text file created or not.

Now you can kick start building the jobs, you will see Jenkins master runs jobs in slave nodes.