Jenkins Slave on AWS EC2 instances with SSH configuration

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

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

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

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

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

After configuring the slave settings, Save the Project. 

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

References:

1. Jenkins Master Configuration on AWS ec2 instance Ubuntu
2. Jenkins Master and Build server on EC2 instance with BeanStalk