What it is
The Book of Secret Knowledge is a large curated repository for engineers, sysops, DevOps practitioners, security researchers, and developers who often need short practical reminders. It collects manuals, cheatsheets, command-line one-liners, tools, search tricks, and resources around Linux, BSD, networking, security, and infrastructure.
The repository was created on GitHub in June 2018. Its format is closer to a personal engineering bookmark book that grew into a public reference. It is not a sequential course; it is a dense collection of “useful command”, “good resource”, and “look here next”.
The name sounds dramatic, but the value is practical. Daily engineering work often requires remembering an openssl command, curl flag, network diagnostic trick, security checklist, or link to a solid manual.
Using it as a working cheatsheet
The best way to read this kind of catalog is task-first: diagnostics, networking, TLS, shell, or security.
## TLS quick checks
- Inspect certificate chain with openssl
- Check supported protocols with nmap
- Verify redirects and headers with curl
## Shell one-liners
- Find large files
- Watch open ports
- Extract fields from logsWhy it is useful
Engineering is full of small repeated tasks. Every tool has its own documentation, search results are noisy, and memory should not store every flag. A catalog like this works as curated memory: it reminds you what tools exist and which commands might be relevant.
It is especially useful at the DevOps/security boundary. When you need to check TLS, HTTP headers, DNS, logs, firewall state, Linux processes, or network routes, one good link or one-liner can save time.
Strengths
The main strength is density. One page brings together many areas usually scattered across bookmarks: manuals, blogs, cheatsheets, security tools, Linux tips, and debugging recipes. For experienced engineers, it is not a textbook; it is a search accelerator.
The second strength is its practical tone. The repository does not try to teach all of networking or security theory, but it offers many entry points that can lead to deeper documentation.
Limits and safety
One-liners are dangerous when copied without understanding. Commands touching networking, filesystems, TLS, firewalls, or security testing can have side effects. Read the man page, understand flags, try commands in a safe environment, and do not run random commands in production without review.
The catalog also does not replace security policy or official documentation. It is useful for orientation and quick reminders, but serious work still needs primary docs, threat models, change management, and reproducible runbooks.