Jenkins fundamental architecture is ‘Master+Slave’ which is distributed in nature.
Master is designed for co-ordination and handling tasks such as scheduling jobs, monitoring slave nodes, dispatching builds to slave nodes, recording and representing the build result and executing build jobs directly.
Slave is designed to perform the work. Agent can run on different operating systems such as Windows and Linux and doesn’t require Jenkins installation on it.
Following document provides details to setup Master Slave configuration in Jenkins. Windows is configured as Master and Linux as Slave node.
Steps to be executed on Master server/Windows
Install Jenkins on Master server
Since the agent node is setup on Linux, it will be launched through ssh.
Secure Shell(ssh) is a network that provides authentication and encrypted data communications between two machines connecting over open network such as the internet.
ssh key authentication is needed to setup agent node.
Generate ssh key
‘id_rsa’ private and ‘id_rsa.pub’ public key will be created in the ‘.ssh’ directory
Steps to be executed on Slave server/Linux
Setup of slave node requires Java to be installed. Install Java from Oracle Website.
Installed java version can be checked by executing ‘java -version’
Set up environmental variables for the installed java
Create a new user Jenkins and user group named Jenkins
sudo useradd jenkins -U -s /bin/bash
set password jenkins
Verify by checking in /etc/passwd and /etc/group files
Configure sudo privileges by configuring in /etc/sudousers
jenkins ALL=(ALL) NOPASSWD: ALL
Command to copy ssh-id from Windows to LINUX
After the generation of ssh key, place the public key into the slave machine’s authorized_keys file by executing below command
C:\Users\admin\.ssh> ssh jenkins@<slave machine IP>”umask 077; test -d .ssh || mkdir .ssh ; cat >> .ssh/authorized_keys || exit 1″ < “umask 077; test -d .ssh || mkdir .ssh ; cat >> .ssh/authorized_keys || exit 1” < C:\Users\admin\.ssh\id_rsa.pub
After the copy of ssh-id to Slave machine > Try logging into the slave machine by executing following command in Jenkins master machine ssh ‘jenkins@<slave machine IP>’.
Setup of Credentials on Jenkins
On Jenkins dashboard click on the Credentials.
Click on Global
Click on Add Credentials
Kind: SSH Username with private Key
Private Key: Enter directly and paste the id_rsa private key
Click on OK
Jenkins user with SSH key is created.
Setup of New Node in Jenkins
Click on Manage Nodes
Click on New Node
Enter Node name LINUX_DEMO, choose Permanent Agent and click OK
- Description: Slave node
- Remote root directory: /home/jenkins
- Launch method: Launch slave agent via SSH
- Host: IP address
- Credentials- Jenkins
- Host Key Verification Strategy – Known hosts file Verification strategy
Click on Save
Slave node LINUX_DEMO is created
Click on Log to see the connection status details
If all the above steps are executed successfully, connection to slave machine will be established.
To test a cross-platform code base with a different operating system, you can configure different OS slaves and run the job against it. Also, a distributed architecture will reduce the load on the master server.
In this blog, we have learned how to setup master slave configuration for Jenkins on different operating systems.