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jenkins controller agent

Prerequisites​

  • Two Ubuntu servers with sudo access and connectivity
    • Controller: 192.168.64.10
    • Agent: 192.168.64.11

Step 1: Install Java (Both)​

Jenkins requires a Java Runtime Environment (JRE) to run

On controller

sudo apt update
sudo apt install openjdk-21-jdk -y
java -version

On agent

sudo apt update
sudo apt install openjdk-17-jdk -y
java --version

sudo systemctl status ssh

Step 2: Install Jenkins (Controller)​

Add repository

sudo wget -O /etc/apt/keyrings/jenkins-keyring.asc https://pkg.jenkins.io/debian-stable/jenkins.io-2023.key
echo "deb [signed-by=/etc/apt/keyrings/jenkins-keyring.asc] https://pkg.jenkins.io/debian-stable binary/" | sudo tee /etc/apt/sources.list.d/jenkins.list > /dev/null

Update and install

sudo apt-get update
sudo apt-get install jenkins -y

Start and enable service

sudo systemctl start jenkins
sudo systemctl enable jenkins
sudo systemctl status jenkins

Initial password

sudo cat /var/lib/jenkins/secrets/initialAdminPassword

Step 3: Generate SSH Key (Controller)​

sudo su - jenkins
ssh-keygen -t rsa -b 4096
cat ~/.ssh/id_rsa.pub
  • Controller stores the private key
  • Agent stores the public key

Step 4: Add Public Key (Agent)​

mkdir -p ~/.ssh
chmod 700 ~/.ssh
touch ~/.ssh/authorized_keys
chmod 600 ~/.ssh/authorized_keys
vim ~/.ssh/authorized_keys  # Paste public key

Step 5: Configure Agent (Controller)​

Get private key

sudo cat /var/lib/jenkins/.ssh/id_rsa

In Jenkins UI

  • Add credentials: SSH Username with private key (ID: agent-ssh-key, Username: ubuntu, Private key: ...)
  • Add node: Name: ubuntu-agent-1, Executors: 1, Remote dir: /home/ubuntu/jenkins-agent-ubuntu, Labels: ubuntu agent, Launch: SSH, Host: 192.168.64.11, Credentials: ubuntu (agent-ssh-key)

Step 5: Test Job​

Freestyle project

  • Label: ubuntu
  • Shell
echo "Hello from Jenkins Agent!"
echo "Running on host: $(hostname)"
echo "Workspace: $(pwd)"
echo "Java version:"
java -version
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