121 Free IT Cheat Sheets: A Complete Library from Beginner to Expert

There's a gap in free IT education that nobody talks about.

Tutorials assume you know nothing. Documentation assumes you know everything. And the space in between — where working professionals actually live — is filled with scattered blog posts, half-finished GitHub repos, and Stack Overflow threads from 2019.

I spent months building something to fix this: a structured library of 121 professional PDF guides that covers 40+ technologies across 4 distinct skill levels. The Dargslan Cheat Sheet Library is completely free — no premium tier, no gated content, no bait-and-switch.

Here's how it works and what's inside.

The Structure: 4 Tiers for 4 Different Needs

The core idea is simple: a first-year junior and a 10-year veteran need fundamentally different resources for the same technology. A beginner needs explanations and context. An expert needs a one-page command reference they can print and pin to their monitor. Most resources try to serve both and end up serving neither.

The library is split into four tiers, each designed for a specific use case.

Quick Reference — 41 One-Page PDFs

These are precision tools. One page per technology, with the most essential commands organized by task. No explanations, no tutorials — just the syntax you need, formatted for instant lookup.

41 technologies covered, including: Linux, Docker, Kubernetes (kubectl + YAML), Git, Python, PostgreSQL, MySQL, AWS CLI, Azure CLI, Terraform, Ansible, Nginx, Bash, SSH, Go, Rust, JavaScript, TypeScript, Java, Redis, MongoDB, Elasticsearch, Kafka, GitHub Actions, Jenkins, PowerShell, Regex, and more.

They're designed for three workflows:

1. Print and pin — tape it next to your monitor for zero-context-switch lookups
2. Digital quick search — keep the PDF open and hit Ctrl+F
3. Team distribution — faster onboarding than sending documentation links

Beginner's Complete Guides — 40 Structured Tutorials

These are full learning resources, not cheat sheets. Each one starts from "what is this technology and why does it matter?" and builds up systematically. No prerequisites, no assumed knowledge.

Every concept includes practical examples with real commands and real output. Each guide is designed for 2–4 hours of focused study — enough to go from zero to confidently using a technology.

40 guides covering every technology in the Quick Reference collection, plus curated learning paths:

For aspiring Linux sysadmins: Linux → Permissions → Bash → SSH → Systemd → Networking → Nginx

For DevOps engineers: Linux → Git → Docker → Docker Compose → Kubernetes → Terraform → Ansible → GitHub Actions

For backend developers: Python or JavaScript → Git → SQL → PostgreSQL → Docker → Redis

For cloud engineers: Linux → Networking → AWS or Azure → Terraform → Ansible → Docker → Kubernetes

Intermediate Guides — 20 Production-Ready Patterns

This tier exists because there's a massive gap between "I can run Docker containers" and "I can run Docker in production." The intermediate guides teach the patterns, practices, and techniques that professional engineers rely on.

Key topics include:

• Docker multi-stage builds, layer optimization, health checks, and security scanning
• Kubernetes RBAC, network policies, ConfigMaps, and horizontal pod autoscaling
• PostgreSQL query optimization with EXPLAIN ANALYZE, indexing strategies, and connection pooling
• Terraform modules, workspaces, remote state backends, and code organization
• Git interactive rebase, bisect debugging, submodules, and reflog recovery
• Python decorators, generators, context managers, type hints, and testing patterns
• Nginx load balancing, caching strategies, rate limiting, and security headers
• Ansible roles, Jinja2 templates, vault encryption, and dynamic inventory

Available for 20 core technologies: Linux, Docker, Kubernetes, PostgreSQL, MySQL, Python, Git, AWS, Azure, Terraform, Ansible, Nginx, Bash, SSH, Vim, PowerShell, Regex, Networking, Permissions, and Docker Compose.

Advanced Guides — 20 Expert Deep Dives

For senior engineers, architects, and technical leads. These cover system internals, architecture patterns, and expert-level techniques that are genuinely difficult to find in free resources anywhere.

Topics that set these apart:

• Linux kernel internals — sysctl tuning, cgroups v2, namespaces, eBPF tracing, custom kernel modules
• Kubernetes at scale — custom controllers and operators, admission webhooks, service mesh integration, etcd management, cluster federation
• Database internals — PostgreSQL WAL mechanics, logical replication, custom extensions (C/PL/pgSQL), query planner deep dives, vacuum tuning
• Container security — Docker BuildKit internals, OCI image specification, rootless containers, Falco/Seccomp profiles
• Language internals — Python metaclasses, descriptors, asyncio internals, CPython bytecode analysis
• Infrastructure architecture — SSH certificate authorities, Terraform custom providers, Nginx OpenResty/Lua scripting, HTTP/3 QUIC

These represent hundreds of hours of production experience condensed into focused, actionable references. They're the kind of knowledge that traditionally required years of trial-and-error in production or expensive conference workshops.

Technology Coverage

20 technologies have complete 4-tier coverage — you can follow a single technology from absolute beginner to expert level:

Linux · Docker · Docker Compose · Kubernetes · PostgreSQL · MySQL · Python · Git · Bash · SSH · Vim · Nginx · AWS · Azure · Terraform · Ansible · PowerShell · Regex · Networking · Permissions

An additional 20+ technologies have Quick Reference + Beginner coverage: JavaScript, TypeScript, Go, Rust, Java, PHP, Ruby, C/C++, Node.js, HTML/CSS, SQL, MongoDB, Redis, Elasticsearch, Kafka, GitHub Actions, Jenkins, Apache HTTPD, Systemd, and Helm.

Intermediate and advanced tiers for these technologies are in active development.

You can see the complete technology coverage map on the Dargslan blog.

Why It's Free

I've spent over a decade in IT, and I've been on both sides of the training gap. I've been the junior who learned everything from free blog posts because my employer had no training budget. And I've been the senior who spent years building personal reference wikis from scattered documentation.

The knowledge to become an excellent IT professional exists freely on the internet. The problem isn't access — it's organization. It's scattered across thousands of pages in different styles, at different quality levels, with no consistent structure or progression.

This library is my attempt to solve the organization problem. Every guide follows the same design principles, uses consistent formatting, and fits into a clear progression from beginner to expert.

I keep it free because I believe that structured, well-designed technical education should be available to everyone — not just those whose employers can afford premium training platforms.

What's Coming Next

The library is a living project. Currently in development:

• Prometheus and Grafana — monitoring and observability at every level
• ArgoCD — GitOps continuous delivery
• Istio — service mesh for Kubernetes
• Go and Rust — intermediate and advanced tiers to complete the coverage

Get Started

The full library is at dargslan.com/cheat-sheets.

You can download individual guides or grab complete bundles — all 41 quick references in one ZIP, all 40 beginner guides, and so on. The only thing we ask is your email, so we can let you know when new guides are published. You can unsubscribe at any time.

If you find the library useful, sharing it with a colleague or your team is the best way to support the project. And if there's a technology or topic you'd like to see covered, I'm always open to suggestions.

Originally published on the Dargslan Blog. Detailed articles for each tier: Quick References · Beginner's Guides · Intermediate Guides · Advanced Guides