Configuration Management

Chef (Week 9)

Chef is a Configuration Management and Infrastructure as Code (IaC) tool used to automate the installation and configuration of software on servers using code. Instead of manually installing software on each server, you write code called recipes and Chef installs automatically.

Why Chef?

Chef Architecture

Model 1: Chef Server Model (Enterprise)

Model 2: Chef Solo / Local Mode

Simpler version with no Chef Server. Recipes stored locally and run using chef-client --local-mode. Best for learning, small projects, or 2–5 servers.

Chef Terminology

Sample Recipe (Ruby DSL)

package 'nginx' do
  action :install
end

service 'nginx' do
  action [:enable, :start]
end

Chef Step-by-Step Procedure

Step 1: Install Chef Workstation

wget https://packages.chef.io/files/stable/chef-workstation/...
sudo dpkg -i chef-workstation_*.deb
chef --version

Step 2: Create Cookbook

chef generate cookbook java_cookbook
# Creates structure:
# java_cookbook/
#   recipes/default.rb
#   metadata.rb

Step 3: Write Recipe

# java_cookbook/recipes/default.rb
package 'openjdk-17-jdk' do
  action :install
end

Step 4: Transfer Cookbook to Node

scp -r java_cookbook ubuntu@<node-ip>:/home/ubuntu/

Step 5: Fix Directory Structure on Node

mkdir ~/cookbooks
mv java_cookbook cookbooks/
# Chef local-mode expects: ~/cookbooks/java_cookbook/

Step 6: Run Chef in Local Mode

sudo chef-client --local-mode -o recipe[java_cookbook]
# Nginx node:
sudo chef-client --local-mode --runlist 'recipe[nginx_cookbook]'

Puppet (Week 10)

Puppet is a Configuration Management and Infrastructure as Code (IaC) tool that manages servers automatically using code instead of manual configuration.

Puppet Architecture — Pull Model

Puppet Terminology

Manifest (.pp file)

package { 'nginx':
  ensure => installed,
}

service { 'nginx':
  ensure => running,
  enable => true,
}

Node-specific Configuration

node 'ec2-nginx' {
  package { 'nginx': ensure => installed }
  service { 'nginx': ensure => running }
}

node default {
  package { 'openjdk-17-jdk': ensure => installed }
}

Puppet Step-by-Step Procedure

Step 1–2: Install Puppet Master & Agents

# On Master (EC2-1):
sudo apt install puppetserver -y
sudo systemctl start puppetserver

# On Nodes (EC2-2, EC2-3):
sudo apt install puppet-agent -y

Step 3: Configure Agent to Point to Master

# On each node — edit puppet.conf:
[main]
server = <master-hostname>

Step 4: Sign Certificates on Master

# On Master — list pending requests:
sudo puppetserver ca list

# Sign all agents:
sudo puppetserver ca sign --all

Step 5: Run Puppet Agent on Nodes

sudo puppet agent -t
# Output: Notice: Applied catalogue in X seconds

Ansible (Week 11)

Ansible (by Red Hat) is an agentless automation and configuration management tool used to install software, configure servers, deploy applications, and manage cloud infrastructure. It uses SSH — no agent installation needed on target nodes.

Why Ansible?

Ansible Architecture — Push Model

Ansible Concepts

Inventory File

[java_servers]
192.168.1.10

[nginx_servers]
192.168.1.20

Playbook (YAML)

- name: Install Java on all java servers
  hosts: java_servers
  become: yes
  tasks:
    - name: Install OpenJDK 17
      apt:
        name: openjdk-17-jdk
        state: present

    - name: Start Java verification
      command: java -version

Key Ansible Commands

# Run a playbook:
ansible-playbook setup.yml

# Test connectivity:
ansible all -m ping

# Run ad-hoc command on all hosts:
ansible all -m shell -a "java -version"

SaltStack (Week 12)

SaltStack is a fast configuration management and remote execution tool that manages large-scale infrastructure using a Master–Minion architecture. It supports both push and pull models and uses ZeroMQ for very fast communication.

Salt Architecture

Push Model (Remote Execution)

# Master pushes command to all minions instantly:
salt '*' test.ping
salt '*' cmd.run 'apt update'

Pull Model (State Application)

# Minions apply states from master:
salt '*' state.apply

Salt State File

# install_java.sls
install_java:
  pkg.installed:
    - name: openjdk-17-jdk

start_java_check:
  cmd.run:
    - name: java -version

SaltStack Setup

# Install Master (EC2-1):
sudo apt install salt-master -y

# Install Minion (EC2-2, EC2-3):
sudo apt install salt-minion -y

# Configure minion to point to master:
# Edit /etc/salt/minion → master: <master-ip>

# Accept minion keys on master:
salt-key -L        # List pending
salt-key -A        # Accept all

# Test:
salt '*' test.ping

Tool Comparison