Catalogue map
Every area, topic and subtopic, with how many entries exist at each level and of each kind. Pick a number to open exactly those entries.
- Guided project
- Build something small from start to finish, step by step.
- Explains an idea
- Plain words on how something works and why.
- Step by step
- Numbered steps to get one task done.
- Cheat sheet
- Commands and options in a table, to look up fast.
- Fixes an error
- An error message, what it means, and how to solve it.
- You are new to this topic.
- You use it, and want to get better.
- You know it well and need the details.
- Repos have no level or kind, so those columns can add up to less than All.
| Level | Kind | Type | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Class | Topic | Beg. | Int. | Adv. | Project | Explainer | How-to | Cheat sheet | Fix | Articles | Scripts | Repos | All |
| 1 | Languages | 29 | 11 | 3 | 3 | 8 | 23 | 4 | 5 | 33 | 10 | 10 | 53 |
| 1.1 | Python | 13 | 5 | 1 | 2 | 5 | 7 | 2 | 3 | 15 | 4 | 5 | 24 |
| 1.1.1 | Basics | 2 | none | 1 | 1 | 1 | none | 1 | none | 3 | none | none | 3 |
| 1.1.2 | Environments & packages | 6 | none | none | 1 | 3 | 1 | none | 1 | 6 | none | 1 | 7 |
| 1.1.3 | Files & automation | 4 | 4 | none | 1 | 1 | 5 | 1 | none | 4 | 4 | 1 | 9 |
| 1.1.4 | Testing | 1 | 1 | none | 1 | none | 1 | none | none | 2 | none | 2 | 4 |
| 1.1.5 | Common errors | 3 | none | none | none | none | none | none | 3 | 3 | none | 1 | 4 |
| 1.2 | JavaScript | 6 | 6 | 2 | 1 | 2 | 7 | 2 | 2 | 8 | 6 | 4 | 18 |
| 1.2.1 | Basics | 4 | none | none | none | 1 | none | 2 | 1 | 4 | none | none | 4 |
| 1.2.2 | Async code | none | 2 | 2 | none | 1 | 3 | none | none | 1 | 3 | 1 | 5 |
| 1.2.3 | Patterns | none | 1 | none | none | none | 1 | none | none | none | 1 | 1 | 2 |
| 1.2.4 | Node.js | 2 | 3 | none | 1 | none | 3 | none | 1 | 3 | 2 | 2 | 7 |
| 1.2.5 | Common errors | 1 | 1 | none | none | none | none | none | 2 | 2 | none | none | 2 |
| 1.3 | TypeScript | 1 | none | none | none | 1 | none | none | none | 1 | none | 1 | 2 |
| 1.3.1 | Basics | 1 | none | none | none | 1 | none | none | none | 1 | none | 1 | 2 |
| 1.4 | Regular expressions | 1 | none | none | none | none | none | 1 | none | 1 | none | none | 1 |
| 1.4.1 | Basics | 1 | none | none | none | none | none | 1 | none | 1 | none | none | 1 |
| 1.5 | Installing languages & tools | 11 | none | none | none | none | 11 | none | none | 11 | none | none | 11 |
| 2 | Version control | 20 | 10 | 1 | 3 | 10 | 9 | 3 | 6 | 28 | 3 | 7 | 38 |
| 2.1 | Git | 15 | 7 | 1 | 2 | 8 | 7 | 1 | 5 | 21 | 2 | 3 | 26 |
| 2.1.1 | Setup | 6 | none | none | 1 | 1 | 3 | none | 1 | 5 | 1 | none | 6 |
| 2.1.2 | Branching & rebasing | 4 | 2 | none | 1 | 4 | none | none | 1 | 6 | none | none | 6 |
| 2.1.3 | Undoing changes | none | 1 | none | none | 1 | none | none | none | 1 | none | none | 1 |
| 2.1.4 | Finding bugs | none | none | 1 | none | none | 1 | none | none | 1 | none | none | 1 |
| 2.1.5 | Housekeeping | 2 | 1 | none | none | 1 | 2 | none | none | 2 | 1 | 1 | 4 |
| 2.1.6 | Reading history | none | none | 1 | none | none | 1 | none | none | 1 | none | none | 1 |
| 2.1.7 | Common errors | 2 | 3 | none | none | none | none | none | 5 | 5 | none | none | 5 |
| 2.1.8 | CI/CD & automation | 4 | 1 | none | 1 | 2 | 2 | none | none | 5 | none | 2 | 7 |
| 2.1.8.1 | Pipelines, runners & hooks | 4 | 1 | none | 1 | 2 | 2 | none | none | 5 | none | 2 | 7 |
| 2.2 | GitHub & collaboration | 6 | 3 | none | 3 | 2 | 2 | 1 | 1 | 9 | none | 2 | 11 |
| 2.2.1 | Pull requests | 4 | none | none | 1 | 2 | 1 | none | none | 4 | none | 1 | 5 |
| 2.2.2 | GitHub Actions | 2 | 3 | none | 2 | none | 1 | 1 | 1 | 5 | none | 1 | 6 |
| 2.3 | Git tools | 1 | none | none | none | none | none | 1 | none | none | 1 | 6 | 7 |
| 3 | Shell & command line | 12 | 3 | none | none | 6 | 4 | 2 | 3 | 14 | 1 | 6 | 21 |
| 3.1 | Shell & Linux | 9 | none | none | none | 6 | 1 | none | 2 | 9 | none | none | 9 |
| 3.1.1 | Basics | 6 | none | none | none | 4 | 1 | none | 1 | 6 | none | none | 6 |
| 3.1.2 | Finding files & text nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 3.1.3 | Text processing nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 3.1.4 | Shell scripting | 1 | none | none | none | none | none | none | 1 | 1 | none | none | 1 |
| 3.1.5 | Backups & syncing nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 3.1.6 | Processes & ports | 2 | none | none | none | 1 | none | none | 1 | 2 | none | none | 2 |
| 3.1.7 | cron & timers | 1 | none | none | none | 1 | none | none | none | 1 | none | none | 1 |
| 3.1.8 | Modern command-line tools nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 3.2 | Command-line tools | 1 | 1 | none | none | none | 1 | 1 | none | 1 | 1 | 6 | 8 |
| 3.3 | SSH & servers | 2 | 2 | none | none | none | 2 | 1 | 1 | 4 | none | none | 4 |
| 3.3.1 | Keys & config | 2 | 2 | none | none | none | 2 | 1 | 1 | 4 | none | none | 4 |
| 4 | Systems & infrastructure | 49 | 25 | 2 | 6 | 31 | 27 | 6 | 6 | 73 | 3 | 29 | 105 |
| 4.1 | Linux administration | 3 | none | none | none | 3 | none | none | none | 3 | none | 1 | 4 |
| 4.1.1 | Services & systemd | 1 | none | none | none | 1 | none | none | none | 1 | none | none | 1 |
| 4.1.2 | Disks, LVM & filesystems | 1 | none | none | none | 1 | none | none | none | 1 | none | none | 1 |
| 4.1.3 | Networking & firewalls nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 4.1.4 | Packages & updates | 1 | none | none | none | 1 | none | none | none | 1 | none | none | 1 |
| 4.1.5 | Users, sudo & hardening nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 4.2 | Containers | 7 | 5 | none | 2 | 3 | 5 | 1 | 1 | 12 | none | 4 | 16 |
| 4.2.1 | Docker basics | 6 | 3 | none | 2 | 3 | 3 | 1 | none | 9 | none | 1 | 10 |
| 4.2.2 | Docker Compose | none | 3 | none | 1 | none | 2 | none | none | 3 | none | 2 | 5 |
| 4.2.3 | Images & registries | 1 | 2 | none | 1 | none | 2 | none | none | 3 | none | 1 | 4 |
| 4.2.4 | Docker fixes | 1 | none | none | none | none | none | none | 1 | 1 | none | none | 1 |
| 4.3 | Proxmox VE | 1 | none | none | none | 1 | none | none | none | 1 | none | none | 1 |
| 4.3.1 | Installation & first steps nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 4.3.2 | VMs & containers nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 4.3.3 | Storage nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 4.3.4 | Clusters & high availability | 1 | none | none | none | 1 | none | none | none | 1 | none | none | 1 |
| 4.3.5 | Backup & restore nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 4.4 | Oracle Private Cloud Appliance | none | 5 | none | none | none | 4 | 1 | none | 5 | none | 1 | 6 |
| 4.4.1 | Architecture & concepts nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 4.4.2 | Compute, networking & storage | none | 4 | none | none | none | 4 | none | none | 4 | none | 1 | 5 |
| 4.4.3 | Administration & monitoring | none | 1 | none | none | none | none | 1 | none | 1 | none | none | 1 |
| 4.5 | KVM & libvirt | 2 | none | none | none | 2 | none | none | none | 2 | none | none | 2 |
| 4.5.1 | Basics | 2 | none | none | none | 2 | none | none | none | 2 | none | none | 2 |
| 4.6 | Kubernetes | 5 | 4 | none | 2 | 2 | 4 | 1 | none | 9 | none | 2 | 11 |
| 4.6.1 | Concepts | 4 | none | none | 1 | 1 | 1 | 1 | none | 4 | none | none | 4 |
| 4.6.2 | Workloads & services | 2 | none | none | 1 | 1 | none | none | none | 2 | none | none | 2 |
| 4.6.3 | Config, secrets & storage | none | 1 | none | none | none | 1 | none | none | 1 | none | none | 1 |
| 4.6.4 | Ingress & networking | none | 1 | none | none | none | 1 | none | none | 1 | none | none | 1 |
| 4.6.5 | Troubleshooting | 1 | none | none | none | none | none | 1 | none | 1 | none | 1 | 2 |
| 4.6.6 | Helm | none | 2 | none | 1 | none | 1 | none | none | 2 | none | 1 | 3 |
| 4.7 | OpenShift & OKD | 2 | 6 | none | 1 | none | 5 | 1 | 1 | 8 | none | 1 | 9 |
| 4.7.1 | Concepts | 1 | 1 | none | 1 | none | 1 | none | none | 2 | none | none | 2 |
| 4.7.2 | Deploying applications | 2 | 5 | none | 1 | none | 5 | 1 | none | 7 | none | 1 | 8 |
| 4.7.3 | Cluster administration | none | 1 | none | none | none | none | none | 1 | 1 | none | 1 | 2 |
| 4.7.4 | Troubleshooting | none | 2 | none | none | none | none | 1 | 1 | 2 | none | none | 2 |
| 4.8 | Automation & infrastructure as code | 2 | 1 | 2 | 1 | 1 | 2 | none | 1 | 4 | 1 | 1 | 6 |
| 4.8.1 | Ansible nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 4.8.2 | Terraform | 2 | 1 | 2 | 1 | 1 | 2 | none | 1 | 4 | 1 | 1 | 6 |
| 4.9 | Monitoring & logging | 3 | 1 | none | none | 4 | none | none | none | 4 | none | 4 | 8 |
| 4.9.1 | Prometheus & Grafana | none | none | none | none | none | none | none | none | none | none | 1 | 1 |
| 4.9.2 | Logs | 2 | none | none | none | 2 | none | none | none | 2 | none | 2 | 4 |
| 4.9.3 | Alerting & dashboards | 1 | 1 | none | none | 2 | none | none | none | 2 | none | 1 | 3 |
| 4.10 | Networking | 6 | 1 | none | none | 5 | 1 | 1 | none | 7 | none | 2 | 9 |
| 4.10.1 | DNS, IP addresses & ports | 3 | none | none | none | 3 | none | none | none | 3 | none | 1 | 4 |
| 4.10.2 | Firewalls | 1 | none | none | none | 1 | none | none | none | 1 | none | 1 | 2 |
| 4.10.3 | SSH | 2 | 1 | none | none | 1 | 1 | 1 | none | 3 | none | none | 3 |
| 4.10.4 | VPN & tunnels nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 4.11 | Backups & recovery | 2 | none | none | none | 2 | none | none | none | 2 | none | 2 | 4 |
| 4.11.1 | Strategy & restore drills | 2 | none | none | none | 2 | none | none | none | 2 | none | none | 2 |
| 4.11.2 | Backup tools | none | none | none | none | none | none | none | none | none | none | 2 | 2 |
| 4.12 | Security | 10 | 2 | none | none | 9 | 2 | none | 1 | 12 | none | 17 | 29 |
| 4.12.1 | Server hardening | 1 | none | none | none | 1 | none | none | none | 1 | none | 2 | 3 |
| 4.12.2 | TLS & certificates | 4 | 1 | none | none | 4 | none | none | 1 | 5 | none | 1 | 6 |
| 4.12.3 | Secrets & access | 2 | none | none | none | 1 | 1 | none | none | 2 | none | 2 | 4 |
| 4.12.4 | Security resources & detection | 3 | none | none | none | 3 | none | none | none | 3 | none | 6 | 9 |
| 4.12.5 | Security testing & CTF | none | 1 | none | none | none | 1 | none | none | 1 | none | 5 | 6 |
| 4.12.6 | Detection & threat hunting | 1 | none | none | none | 1 | none | none | none | 1 | none | 6 | 7 |
| 4.13 | Windows & PowerShell | 8 | 2 | none | none | 1 | 6 | 1 | 2 | 8 | 2 | 2 | 12 |
| 4.13.1 | PowerShell | 5 | 1 | none | none | 1 | 3 | 1 | 1 | 4 | 2 | 1 | 7 |
| 4.13.2 | WSL | 2 | 1 | none | none | none | 2 | none | 1 | 3 | none | none | 3 |
| 4.13.3 | Windows administration | 5 | 2 | none | none | none | 5 | none | 2 | 5 | 2 | 1 | 8 |
| 5 | Data | 23 | 14 | 1 | 2 | 15 | 8 | 7 | 6 | 33 | 5 | 8 | 46 |
| 5.1 | SQL | 9 | 3 | 1 | 1 | 8 | 1 | 2 | 1 | 12 | 1 | 2 | 15 |
| 5.1.1 | Queries | 7 | 2 | none | 1 | 4 | 1 | 2 | 1 | 8 | 1 | 2 | 11 |
| 5.1.2 | Joins | 3 | 1 | none | 1 | 2 | none | 1 | none | 3 | 1 | none | 4 |
| 5.1.3 | Indexes & performance | 1 | none | 1 | none | 2 | none | none | none | 2 | none | none | 2 |
| 5.2 | CSV & JSON | 6 | 1 | none | none | 3 | 2 | 1 | 1 | 4 | 3 | 1 | 8 |
| 5.2.1 | jq & JSON on the command line | none | 1 | none | none | none | none | 1 | none | none | 1 | 1 | 2 |
| 5.3 | Data analysis | none | 1 | none | none | none | 1 | none | none | 1 | none | 2 | 3 |
| 5.4 | PostgreSQL | 2 | 3 | none | 1 | none | 2 | 1 | 1 | 5 | none | 1 | 6 |
| 5.4.1 | Install & connect | 2 | 1 | none | none | none | 2 | 1 | none | 3 | none | 1 | 4 |
| 5.4.2 | Roles & administration | 1 | 1 | none | none | none | none | 1 | 1 | 2 | none | none | 2 |
| 5.4.3 | Backup & restore nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 5.4.4 | Performance & tuning nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 5.4.5 | Replication & high availability nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 5.5 | MySQL & MariaDB | 1 | none | none | none | none | none | 1 | none | 1 | none | 2 | 3 |
| 5.5.1 | Administration | 1 | none | none | none | none | none | 1 | none | 1 | none | none | 1 |
| 5.5.2 | Backup & restore nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 5.5.3 | Replication nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 5.6 | Oracle Database | 1 | 5 | none | none | 1 | 2 | 1 | 2 | 5 | 1 | none | 6 |
| 5.6.1 | Concepts & tools | 1 | 2 | none | none | 1 | none | 1 | 1 | 3 | none | none | 3 |
| 5.6.2 | Administration | none | 5 | none | none | none | 2 | 1 | 2 | 4 | 1 | none | 5 |
| 5.6.3 | Backup with RMAN | none | 1 | none | none | none | 1 | none | none | 1 | none | none | 1 |
| 5.7 | MongoDB | 2 | 1 | none | none | 1 | none | 1 | 1 | 3 | none | 1 | 4 |
| 5.7.1 | Basics | 2 | 1 | none | none | 1 | none | 1 | 1 | 3 | none | none | 3 |
| 5.7.2 | Administration | none | 1 | none | none | none | none | none | 1 | 1 | none | 1 | 2 |
| 5.8 | Redis | 1 | none | none | none | none | none | 1 | none | 1 | none | none | 1 |
| 5.8.1 | Basics | 1 | none | none | none | none | none | 1 | none | 1 | none | none | 1 |
| 5.8.2 | Administration & persistence nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 5.9 | Database operations | 3 | 3 | none | none | 3 | 1 | none | 2 | 5 | 1 | none | 6 |
| 5.9.1 | Choosing a database | 3 | none | none | none | 3 | none | none | none | 3 | none | none | 3 |
| 5.9.2 | Security & access | none | 3 | none | none | none | 1 | none | 2 | 2 | 1 | none | 3 |
| 6 | Web | 12 | 8 | 1 | 1 | 11 | 5 | 2 | 2 | 17 | 4 | 9 | 30 |
| 6.1 | HTTP & APIs | 10 | 8 | 1 | 1 | 9 | 5 | 2 | 2 | 15 | 4 | 3 | 22 |
| 6.1.1 | Making requests | 6 | 6 | 1 | 1 | 5 | 5 | 1 | 1 | 9 | 4 | 3 | 16 |
| 6.1.2 | Status codes | 2 | 2 | none | 1 | 1 | none | 1 | 1 | 4 | none | none | 4 |
| 6.1.3 | Authentication | 3 | 1 | none | none | 3 | 1 | none | none | 3 | 1 | none | 4 |
| 6.2 | CSS | none | none | none | none | none | none | none | none | none | none | 1 | 1 |
| 6.2.1 | Layout | none | none | none | none | none | none | none | none | none | none | 1 | 1 |
| 6.2.2 | Selectors & specificity nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 6.3 | HTML & accessibility nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 6.3.1 | Accessibility nothing yet | none | none | none | none | none | none | none | none | none | none | none | none |
| 6.4 | Web frameworks | none | 1 | none | none | none | none | none | 1 | 1 | none | 3 | 4 |
| 6.5 | References | 1 | none | none | none | none | none | 1 | none | 1 | none | 1 | 2 |
| 6.6 | Web servers & reverse proxies | 2 | 2 | none | none | 2 | 1 | 1 | none | 4 | none | 2 | 6 |
| 6.7 | Deploying sites | none | none | none | none | none | none | none | none | none | none | 1 | 1 |
| Whole catalogue | 130 | 60 | 7 | 11 | 81 | 59 | 22 | 24 | 177 | 20 | 61 | 258 | |
Missing a topic? Anyone can add one while writing an entry; trusted editors tidy the tree.