Cheatsheet Index

Every page on the site that is useful as a fast lookup during a ticket. Grouped by topic. When you are mid-incident, you want this page open in a second tab.

Ansible

• Ansible Cheatsheet — CLI flags, ad-hoc modules, task/handler boilerplate, loops, precedence, Jinja filters, vault.
• Review checklist — paste into every MR template.
• Anti-pattern table — grep for these before you ship.
• Variable precedence table — where does this var come from?
• Error handling patterns — block/rescue/always, failed_when, assert.
• Performance knobs — forks, pipelining, strategies, fact caching.
• Tags reference — selective runs and inheritance.

Services

• Service Cheatsheets (hub) — quick-reference one-pagers for common services.
• Nginx / Nginx Config / Nginx Reverse Proxy
• Apache / Apache GSSAPI SSO
• Postfix / Postfix Config / Postfix TLS & DKIM
• Dovecot / Dovecot Sieve & Quotas
• Rsyslog / Rsyslog Forwarding
• Squid / Squid SSL-Bump
• Chrony — time sync commands.

Platform

• systemd & journalctl / systemd Unit Authoring
• SELinux / SELinux Debugging
• firewalld / firewalld Rich Rules
• Linux Networking / Bonding & Bridges
• LVM / LVM Thin & Snapshots

Identity

• Kerberos commands — kinit/klist/kdestroy, common errors.
• Keytab Rotation — KVNO bumps, ktutil recipes.
• SSSD & Auth Flow — PAM/NSS/SSSD order, sssd.conf debugging.
• FreeIPA / HBAC & Sudo / Replication / Dogtag Certs
• Windows 11 + FreeIPA / FreeIPA CLI on Windows

Linux tools

• Linux CLI — navigation, perms, services, networking, DNS, packages.
• Bash Scripting — set -euo pipefail, traps, common patterns.
• lsof & strace — find what's listening, debug open files, trace syscalls.
• Wireshark & tshark — capture vs display filters, follow streams.
• NMAP — host discovery, service detection, NSE.
• rsync — safe flags, SSH transport, --delete, --dry-run.
• cron & Timers — syntax, logging, @reboot caveats.

Certificates & TLS

• Certificates — openssl commands, expiry checks, formats.
• PKI Design — root vs intermediate, SANs vs CN, OCSP.
• SSH Keys / SSH CA Certs
• ACME & Certbot

GitLab & CI

• CI/CD Pipelines — .gitlab-ci.yml structure, cache, needs, matrix.
• Merge Requests — reviewing diffs, approvals, squash/rebase.
• Git for Infra — branch conventions, reverting bad merges.
• CI for Ansible — lint + syntax + molecule + check-mode skeleton.
• Secrets & OIDC
• Runner Setup

Troubleshooting flows

• Troubleshooting Workflow — the top-level "what do I do now" checklist.
• Service Troubleshooting — per-service diagnosis steps.
• Generic — reusable cross-ticket cheat sheet.
• Incident: First 15 Minutes
• Change Window Runbook

Data plane & backup

• Backup & Restore
• Postgres Ops / Postgres Backup
• MySQL Ops / MySQL Backup
• Redis Ops

Observability

• Observability Overview
• Prometheus & node_exporter
• Grafana Basics
• Loki Logs
• SLOs & On-Call

Reference

• Site Map — every page grouped by section.
• Glossary — short definitions of terms and tools.
• Start Here — the recommended reading order.