DevOps Fundamentals¶

📖 DevOps Roadmap - DevOps learning path 📖 Git Documentation - Official Git reference

DevOps Overview¶

What is DevOps?¶

• Cultural and technical approach combining Development and Operations
• Goals: faster delivery, improved reliability, better collaboration
• Key principles: automation, CI/CD, monitoring, collaboration, IaC
• Not a role or tool - it is a practice and culture

DevOps Lifecycle¶

Plan -> Code -> Build -> Test -> Release -> Deploy -> Operate -> Monitor
  ^                                                                  |
  |__________________________________________________________________|

Key DevOps Practices¶

Version Control with Git¶

Git Basics¶

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Configuration:

git config --global user.name "Your Name"
git config --global user.email "you@example.com"

Repository Operations:

git init                    # initialize new repository
git clone url               # clone remote repository

Daily Workflow:

git status                  # check changed files
git add file                # stage specific file
git add .                   # stage all changes
git commit -m "message"     # commit staged changes
git push                    # push to remote
git pull                    # pull from remote (fetch + merge)

Branching:

git branch                  # list branches
git branch feature-x        # create branch
git checkout feature-x      # switch to branch
git checkout -b feature-x   # create and switch
git merge feature-x         # merge branch into current
git branch -d feature-x     # delete branch (after merge)

Viewing History:

git log                     # commit history
git log --oneline           # condensed history
git diff                    # unstaged changes
git diff --staged           # staged changes

Git Workflow¶

Feature Branch Workflow: 1. Create feature branch from main: git checkout -b feature/login 2. Make changes and commit: git add . && git commit -m "Add login" 3. Push branch: git push origin feature/login 4. Create pull request for code review 5. Merge to main after approval 6. Delete feature branch

Key Concepts: | Concept | Description | |---------|-------------| | Repository | Project with complete history | | Branch | Independent line of development | | Commit | Snapshot of changes with message | | Pull Request | Request to merge changes (review) | | Merge | Combine branches together | | Remote | Server-hosted repository (GitHub, GitLab) | | Clone | Local copy of a remote repository |

Git Hosting Platforms¶

CI/CD (Continuous Integration / Continuous Delivery)¶

Pipeline Stages¶

Source -> Build -> Test -> Deploy (Staging) -> Deploy (Production)

CI vs CD¶

CI/CD Tools¶

Infrastructure as Code (IaC)¶

What is IaC?¶

• Define infrastructure using code files instead of manual setup
• Version controlled, reviewable, repeatable
• Eliminates manual configuration errors
• Enables rapid provisioning and scaling

IaC Tools¶

Terraform Example:

resource "aws_instance" "web" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
  tags = {
    Name = "web-server"
  }
}

IaC Benefits¶

• Reproducibility - Same code creates same infrastructure
• Version control - Track changes over time
• Automation - No manual steps
• Documentation - Code is the documentation
• Testing - Can validate before applying

Configuration Management¶

What is Configuration Management?¶

• Automate the installation and configuration of software on servers
• Ensure all servers are in a desired state
• Detect and correct configuration drift

Configuration Management Tools¶

Ansible Example (Playbook):

---
- hosts: webservers
  tasks:
    - name: Install nginx
      apt:
        name: nginx
        state: present
    - name: Start nginx
      service:
        name: nginx
        state: started
        enabled: yes

Key Differences: - Ansible is agentless (uses SSH) - simplest to get started - Puppet/Chef require agents installed on target servers - Ansible uses YAML (human-readable), Puppet uses its own DSL

Monitoring and Observability¶

Three Pillars of Observability¶

Monitoring Tools¶

Site Reliability Engineering (SRE)¶

Key SRE Concepts¶

Example: - SLI: "99.95% of HTTP requests return successfully" - SLO: "Maintain 99.9% availability per month" - SLA: "If below 99.9%, customer receives service credit"

Key Facts for the Exam¶

1. Git workflow: clone -> branch -> commit -> push -> pull request -> merge
2. CI builds and tests on every commit, CD automates deployment
3. Terraform is multi-cloud IaC, CloudFormation is AWS-only
4. Ansible is agentless (SSH), Puppet and Chef require agents
5. Three pillars of observability: metrics, logs, traces
6. SLA is customer-facing, SLO is internal target
7. IaC enables version-controlled, repeatable infrastructure
8. Feature branches isolate work and enable code review via pull requests