Jenkins Slave on AWS EC2 instances with SSH configuration

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After configuring the  Jenkins Master we need to configure the slave or agent on EC2 instance. There are various methods to connect with the Slave node. In this post, 

I would like to share the SSH key-based remoting method.

Pre-requisites

  • Jenkins Master already Up and Running
  • Java (JDK) installed on the Slave node


Jenkins master slave configuration on EC2

Here we are in the slave machine and proceed with the following steps for configure a SSH based Jenkins slave.

How to create user and generate ssh-key on Slave?

Login to slave node terminal using ssh or PuTTY switch to root user. 
useradd jenkins_slave
mkdir -p /home/jenkins_slave
usermod -d /home/jenkins_slave jenkins_slave
tail -1 /etc/passwd # To check useradded to userlist
Now switch to the newly created user 'jenkins_slave'. 
sudo su - jenkins_slave
SSH Key generate for 'jenkins_slave' user with the following command: 
cd .ssh
ssh-keygen -t rsa -N ""
The above command will create two files in /home/jenkins_slave/.ssh folder id_rsa (private key) and id_rsa.pub (public key). Now navigate to the .ssh folder then push the public key content into authorized_keys file. 
cat id_rsa.pub>authorized_keys
Now make the authorized_keys file permission to 700. 
chmod 600 authorized_keys

How to Configure known_hosts on Master node?

Login to the "Master machine" and switch to user 'jenkins' and then create .ssh folder. Add the slave host to the known_hosts file using following command(ssh-keyscn). 
cd .ssh;
ssh-keyscan -H 172.31.37.235>>known_hosts
chmod 600 known_hosts
Jenkins Master node ssh-keyscan


All set on the master node about the slave node. Now go to the Jenkins dashboard. On the left pane select the "Manage Jenkins" > Manage Nodes and Cloud > New Node Enter the following values:

    1. Name: node1
    2. Description: Build server
    3. # of executors: 5
    4. Remote root directory: /tmp/slave 
    5. Labels: node1
    6. Usage: Use this node as much as possible
    7. Launch method : Launch agents via SSH
    a. Host: ip-address
    b. Credentials: jenkins_slave
    c. Host Key Verification Strategy: Known host file Verification Strategy
        1. Availability: Keep this agent online as much as possible

        Node configuration on Jenkins


        Now go to the slave node and fetch the content of the id_rsa file (that is private key content).

        ssh-key private key

        In the Jenkins Dashboard  - On the left pane section select : Credentials 

        Global Credentials(unrestricted)

        Add Jenkins Global credentials
        Scope: Global
        Username : jenkins_slave (which was created in the above top step)
        Private key copy the above content to the Jenkins Private key Text box from the slave node ~/.ssh/id_rsa

        Global credentials

        After configuring the slave settings, Save the Project. 

        Finally, you can see the Node is active state as shown below:

        Active Node on Jenkins



        References:




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