DevOps Classroom notes 22/Jul/2025

Why Configuration Management

• Consider a scenario where your organization is building an ecommerce application
• System overview
  
• To run this application, we need two ubuntu linux servers
  • db server: configuring this server involves
    • update linux
    • add necessary users on linux
    • install postgres
    • configure postgres to create a database and user
  • application server:
    • update linux
    • add necessary users on linux
    • install java
    • install tomcat
    • deploy your application
      
• Now to ensure the application is deployed on every change to ST environment (also other environments). Possible options
  • Manual: It is time consuming
  • Automation: Its a better approach
• How to do this automation and what are possible ways?
  • Procedural: It is expressed in a procedural way where we define steps on how to do.
    • Example: Scripting
    • lets say we want to install apache server
      bash
sudo apt update
sudo apt install apache2 -y
sudo systemctl enable apache2
sudo systemctl start apache2
  • Declarative: It is expressed in a declartive way where we define a desired state (what we want)
    • Example: Configuration Management using Ansible, Chef, Puppet
      ensure package definitions are upto date
ensure apache is present
ensure apache is enabled
ensure apache is running
      
      
• Declarative approach ensures we get same result on every execution, This property is called as idempotence.
• Configuration Management is a software which allows to configure systems in a declarative approach and ensure idempotence.
• Softwares:
  • Ansible
  • Chef
  • Puppet
  • Salt

Steps for Learning Configuration Mangement using Ansible

• Good with command line
• Ensuring whatever you are automating you know how to do it manually.
• Learning YAML & Ansible concepts

Linux Basics

• Kernel: It is core of the operating system, It enables hardware integrations.
• Distributions: Most of the linux distributions are from
  • debian:
    • ubuntu
    • kali linux
    • mint
  • redhat (fedora)
    • redhat enterprise linux
    • amazon linux
    • rocky linux
• Distributions add softwares and will have package manager.
  • debian => apt
  • redhat => yum (dnf)
• Shell: It helps in interacting with kernel by executing commands (application)
  
  
• Exercise: What is daemon in linux?