Editing Jenkins Node Addition

= Jenkins Node Addition and Configuration Guide =

This guide describes how to add and configure a new Jenkins node, install Java 11 on it, configure SSH keys, and connect it successfully to the Jenkins master.

== 1. Install Java 11 on the New Node ==
On the new Jenkins node server, install Java 11 (required for Jenkins agents to run).

Example (Debian/Ubuntu):
 apt update
 apt install openjdk-11-jdk -y

Verify installation:
 java -version

== 2. Configure SSH Keys for Jenkins Connection ==
Jenkins communicates with the node over SSH. We use the Jenkins master’s SSH key to connect to the node.

=== Step 2.1: Locate the Jenkins Master SSH Key ===
On the Jenkins master server, the SSH key pair for Jenkins is typically stored in:
 /var/lib/jenkins/.ssh/id_rsa   (private key)
 /var/lib/jenkins/.ssh/id_rsa.pub   (public key)

=== Step 2.2: Add Jenkins Master Public Key to Node ===
On the node server, add the Jenkins master’s public key to:
 /var/lib/jenkins/.ssh/authorized_keys

Ensure correct permissions:
 chmod 700 /var/lib/jenkins/.ssh
 chmod 600 /var/lib/jenkins/.ssh/authorized_keys
 chown -R jenkins:jenkins /var/lib/jenkins/.ssh

== 3. Add Jenkins Node in Jenkins UI ==
1. Open Jenkins master web UI.
2. Go to **Manage Jenkins → Nodes → New Node**.
3. Enter the node name (e.g., ci-node).
4. Select "Permanent Agent".
5. Configure:
   - Remote root directory: `/var/lib/jenkins`
   - Number of executors: `2`
   - Labels: `ci-node`
   - Launch method: "Launch agents via SSH"

== 4. Configure Node SSH Credentials ==
1. In Jenkins, go to **Manage Jenkins → Credentials → (Global)**.
2. Add new credentials:
   - Kind: SSH Username with private key
   - Username: jenkins
   - Private key: Enter directly → paste contents of:
     /var/lib/jenkins/.ssh/id_rsa  (from Jenkins master)
3. Save credentials.

== 5. Link Node with Credentials ==
In the node configuration page:
1. Set the host to the node's IP address.
2. Select the SSH credentials saved earlier.
3. Save the node configuration.

== 6. Update /etc/hosts (If Required) ==
If the node or deployment server requires name resolution, update the `/etc/hosts` file on both servers to map hostnames to IPs.

Example:
 192.168.1.100   ci-node

== 7. Permissions on Node ==
Ensure that the Jenkins user on the node has:
- Access to `/var/lib/jenkins`
- Proper ownership and permissions for SSH files
- Ability to run Java 11

== 8. Verify Connection ==
After saving the configuration, Jenkins will attempt to connect to the node:
- Logs will display Java startup commands
- If successful, status will show "Agent connected"

== Final Result ==
Once connected, the node will be available for Jenkins builds and deployments.
You can now assign jobs to run on this node by using the label: ci-node