Course: Introduction to DevOps

1. What is DevOps?

DevOps is a cultural and technical movement that aims to bridge the gap between development (Dev) and operations (Ops) teams. It emphasizes collaboration, automation, measurement, and sharing to deliver software faster and more reliably.

1.1 The CALMS Framework

CALMS is the foundational framework for understanding DevOps:

• C - Culture: Shared responsibility, collaboration, trust, and blameless post-mortems.
• A - Automation: Automate repetitive tasks — builds, tests, deployments, infrastructure provisioning.
• L - Lean: Apply lean principles — reduce waste, amplify learning, decide as late as possible, deliver as fast as possible.
• M - Measurement: Measure everything — lead time, deployment frequency, MTTR, change failure rate.
• S - Sharing: Share knowledge, tools, and practices across teams.

1.2 The Three Ways (Gene Kim)

Gene Kim, author of The Phoenix Project, defined The Three Ways:

1. Flow / Systems Thinking: Optimize the entire value stream, not just individual silos.
2. Feedback Loops: Create rapid feedback from operations back to development.
3. Continuous Learning: Foster a culture of experimentation, risk-taking, and continuous improvement.

2. History of DevOps

2.1 Pre-DevOps Era (Before 2007)

• Development and Operations were strictly separated.
• "Throw it over the wall" mentality.
• Deployments were rare, risky, and manual.
• Waterfall methodology dominated.

2.2 The 2009 DevOpsDays

• October 2009: Patrick Debois organized the first DevOpsDays in Ghent, Belgium.
• The term "DevOps" was coined as a contraction of "Development" and "Operations".
• John Allspaw and Paul Hammond's presentation "10+ Deploys Per Day: Dev and Ops Cooperation at Flickr" was a seminal influence.

2.3 Key Milestones

2.4 The Phoenix Project

The Phoenix Project (2013), by Gene Kim, Kevin Behr, and George Spafford, is a business novel that illustrates DevOps principles through the story of an IT manager named Bill Palmer. Key takeaways:

• IT is not a cost center but a value creator.
• The Three Ways provide a path to transformation.
• DevOps is about improving the entire value stream.

3. DORA Metrics

The DevOps Research and Assessment (DORA) team identified four key metrics that measure DevOps performance:

3.1 The Four Key Metrics

3.2 Capabilities Driving Performance

DORA research identified 25+ capabilities that predict software delivery performance:

• Continuous Delivery: Branching, CI, trunk-based development
• Architecture: Loosely coupled teams and systems
• Product: Customer-centric approach, visibility of work
• Lean: Small batch sizes, limiting WIP
• Culture: Generative culture (Westrum model), job satisfaction

4. DevOps vs SRE vs Platform Engineering

4.1 Site Reliability Engineering (SRE)

SRE applies software engineering principles to operations. Core concepts:

• Service Level Indicators (SLIs): Measured metrics (latency, error rate, throughput).
• Service Level Objectives (SLOs): Target values for SLIs.
• Service Level Agreements (SLAs): Contracts with consequences for SLO breaches.
• Error Budgets: (1 - SLO) defines how much "unreliability" is allowed.
• Toil: Manual, repetitive, automatable work — SREs aim to keep toil below 50%.

4.2 Platform Engineering

Platform Engineering focuses on building internal developer platforms (IDPs) that abstract infrastructure complexity:

• Developer Experience (DX): Self-service capabilities, golden paths.
• Backstage: Spotify's open-source platform builder (CNCF).
• Crossplane: Control plane platform framework.
• Humanitec, Port, Cortex: Commercial platform tools.

4.3 Comparison

5. Learning Roadmap

5.1 Chapter Progression

00 - Introduction   →  01 - Linux   →  02 - Docker   →  03 - Kubernetes
                                                                      ↓
06 - AWS →  05 - Terraform  →  04 - CI/CD
07 - GCP ↗                  ↗
08 - Azure ↗

5.2 Prerequisites

• Basic command-line proficiency
• Understanding of software development lifecycle
• Familiarity with version control (Git)

5.3 Estimated Time per Chapter

6. DevSecOps

Security is integrated throughout the DevOps lifecycle, not bolted on at the end:

• Shift Left: Security testing early in development.
• Policy as Code: Automated compliance (OPA, Sentinel).
• Supply Chain Security: SBOM, Sigstore, Cosign.
• Runtime Security: Falco, AppArmor, seccomp.

7. GitOps

GitOps uses Git as the single source of truth for declarative infrastructure and applications:

• Principles: Declarative, versioned, immutable, automatically reconciled.
• Tools: ArgoCD, Flux, Rancher Fleet.
• Benefits: Audit trail, rollback, team collaboration.

Summary

DevOps is a cultural and technical movement that has evolved significantly since 2009. The CALMS framework and The Three Ways provide the philosophical foundation. DORA metrics offer a way to measure performance. Modern practices like SRE and Platform Engineering complement DevOps rather than replace it. This curriculum builds from Linux fundamentals through containers, orchestration, CI/CD, infrastructure as code, and cloud platforms.