Sefism DevOps and Cloud Cheat Sheet

What this cheat sheet is

The DevOps and cloud cheat sheet is the quick-revision companion to Sefism's DevOps and cloud roadmap. It puts Linux, Git workflows, networking, Docker, AWS, Terraform, CI/CD, Kubernetes, observability and security basics in one place: ten chapters and 79 concepts, with an A to Z glossary of 142 further terms.

It is written for the moment before you touch a server, a pipeline or a cluster. Each concept says what it is and why it matters, 22 of them include a command or config snippet, and many name the mistake that causes real incidents. There is one edition for everyone.

Chapter by chapter

1. Linux, the shell and scripting (8 concepts)

File permissions, users, groups and sudo, processes and signals, systemd services, system logs, pipes with grep, sed and awk, safe Bash scripts, and cron and systemd timers. Most concepts here come with the commands you actually type.

2. Git workflows (6 concepts)

Branches and pull requests, merge versus rebase, trunk-based development, undoing changes with revert or reset, tags and semantic versioning, and .gitignore and secrets in Git. In DevOps, infrastructure and pipeline definitions live in Git too, so this chapter matters as much as any cloud one.

3. Networking for engineers (8 concepts)

IP addresses, subnets and CIDR, TCP, UDP and ports, DNS records, HTTP, TLS and certificates, firewalls, SSH and key-based login, Nginx as a reverse proxy and load balancer, and debugging with dig, curl, ss and traceroute. The chapter's premise: most outages that look like app bugs are DNS, ports, firewalls or certificates.

4. Containers with Docker (9 concepts)

Containers versus virtual machines, images, layers and tags, the Dockerfile, layer caching and instruction order, multi-stage builds, volumes and bind mounts, Docker Compose, registries and container networking.

5. Cloud on AWS: the core services (11 concepts)

Regions and availability zones, the shared responsibility model, IAM users, roles and policies, EC2 and EBS, VPC, subnets and NAT, security groups and network ACLs, S3, load balancers and Auto Scaling, RDS, Lambda, SQS and other managed building blocks, and CloudWatch. The sheet notes that the ideas carry over to Azure and Google Cloud under different names.

6. Infrastructure as code with Terraform (6 concepts)

What infrastructure as code is, the init, plan and apply workflow, Terraform state, remote state and locking, modules, variables and outputs, and environments, drift and import.

7. CI/CD pipelines (7 concepts)

Continuous integration, continuous delivery versus continuous deployment, GitHub Actions workflows, pipeline stages and building once, secrets and OIDC in pipelines, config in the environment, and rolling, blue-green and canary deploys.

8. Kubernetes and GitOps (10 concepts)

Cluster architecture, pods, Deployments and ReplicaSets, Services, ConfigMaps and Secrets, Ingress and the Gateway API, resource requests and limits, liveness, readiness and startup probes, the Horizontal Pod Autoscaler, and Helm with GitOps through Argo CD.

9. Observability and incident response (8 concepts)

Metrics, logs and traces, Prometheus and PromQL, golden signals and Grafana dashboards, centralised logging, tracing with OpenTelemetry, SLOs and error budgets, alerting that respects on-call, and incident roles with blameless postmortems.

10. Security basics (6 concepts)

Least privilege, secrets management, image scanning and supply chain security, container hardening, patching and updates, and encryption in transit and at rest: the habits that prevent most real-world breaches in cloud and DevOps work.

Nine rules of thumb

• If you did it twice by hand, script it; if it matters in production, put it in Git.
• Debug networks layer by layer: DNS, then port, then process, then HTTP, then the app.
• Build an artifact once and promote the same one through every environment.
• Read every Terraform plan before applying, and stop at any unexpected destroy or replace.
• Prefer short-lived credentials from roles and OIDC over stored access keys.
• Tag images with a version or commit SHA, never deploy latest.
• Alert on symptoms users feel, not on every metric that moves.
• Practise restores: a backup you have never restored is only a hope.
• Keep costs visible: tag resources and set a billing alarm on day one.

How to use it with the roadmap

The roadmap's seven stages line up with the chapters: Linux with chapter 1, networking with chapter 3, Docker with chapter 4, AWS with chapter 5, infrastructure as code and CI/CD with chapters 6 and 7, Kubernetes with chapter 8, and observability with chapter 9. Git workflows and security basics run through every stage.

• After each stage: read the matching chapter and explain each concept without notes; redo any snippet you could not have written yourself.
• Before a change in production: skim the relevant chapter's pitfalls, then the rules of thumb. Reading a Terraform plan or a probe definition with those in mind catches a lot.
• During an incident drill: chapter 3's debugging order and chapter 9's incident roles are the two pages to have open.
• Before a DevOps technical round: chapters 4, 6 and 8 cover topics that come up often, such as image layers, Terraform state and probes.

How it works on Sefism

The public page at /cheatsheets/devops-cloud/ shows every chapter's title and introduction, with the first chapters open to read in full. Everything on Sefism is free to learn from. Keeping a cheat sheet uses credits; new members get starting credits, and anyone learning seriously who runs out can ask for more. Keeping the sheet opens every chapter in the member area.

Following the DevOps and cloud roadmap also unlocks this sheet, and your first roadmap is free. Roadmap topics link to the concepts here that cover them.

Related on Sefism

• The DevOps and cloud roadmap this sheet accompanies.
• The Cloud engineering cheat sheet and Platform engineering and SRE cheat sheet for the next step.
• The Linux Command Line and Pro Git for chapters 1 and 2.
• Kubernetes documentation and Killercoda for chapter 8.
• What is platform engineering, and how is it different from DevOps?

Frequently asked questions

Is this sheet only for AWS? The cloud chapter uses AWS names because the roadmap teaches AWS, but the sheet notes the ideas carry over to Azure and Google Cloud. The other nine chapters are not tied to a provider.

Does it cover Ansible or Jenkins? Not as chapters. It follows the roadmap's stack: Terraform for infrastructure and GitHub Actions for pipelines. Ansible appears as a glossary entry, and the CI/CD concepts apply to any pipeline tool.

Can I use it to prepare for a Kubernetes certification? It is a revision aid, not exam material. Chapter 8 covers the core objects and practices, and links to the Kubernetes documentation and hands-on labs for depth.