Filesystem Tunnels
A shared server contains unfamiliar files and permissions that must be handled safely.
- 8 practical command rooms
- 1 multi-step boss workflow
- Immediate explanations and safety notes
CURRICULUM // LINUX
Linux Undergrid
Navigate files, control processes, transform text, and diagnose a living system.
LI48 CHALLENGES · 3 LEVELS
FOUR-ZONE PATH
From first command to incident recovery.
Each zone turns reference material into an active scenario. You will choose commands, repair mistakes, predict outcomes, and assemble complete workflows.
Process Engine
A service is behaving badly and the surrounding process environment holds the clues.
- 8 practical command rooms
- 1 multi-step boss workflow
- Immediate explanations and safety notes
Text Foundry
Large logs hide a small but important signal. Find it and reshape it into useful output.
- 8 practical command rooms
- 1 multi-step boss workflow
- Immediate explanations and safety notes
Operations Deck
Storage, archives, and network paths must be inspected before the host runs out of room.
- 8 practical command rooms
- 1 multi-step boss workflow
- Immediate explanations and safety notes
PRACTICE DESIGN
Every zone teaches a different operational decision.
The multi-step sequences below are authored workflows, while individual command rooms link to the closest available command reference.
Filesystem Tunnels
Create a private log directory and file with deliberate permissions.
Confirm the location, create the hierarchy and file, then restrict directory traversal and file access separately.
Boss incident
Audit and secure a configuration file that may expose credentials. Locate and inspect the file before restricting it to its owner, then verify the final permission bits.
Read the complete field guide →Process Engine
Stop a misbehaving process gracefully and verify that it exited.
Discover the process and its PID before sending SIGTERM, allow cleanup time, then verify whether it remains.
Boss incident
Diagnose a failing nginx service before deciding whether its process must be stopped. Service status and logs provide evidence before process lookup and a graceful stop; the final status confirms the outcome.
Read the complete field guide →Text Foundry
Extract error lines from a log, normalize their order, and produce a reusable report.
Filter first, sort before deduplication, count the resulting report, then preview a bounded sample.
Boss incident
Find repeated failed-login sources in an authentication log without modifying the original. Create derived files, extract the source field, sort before counting duplicates, and rank the final counts numerically.
Read the complete field guide →Operations Deck
Investigate disk pressure and archive a large application log directory safely.
Measure filesystem and directory usage, create the archive, inspect its contents, then confirm its size and location.
Boss incident
Diagnose why an HTTPS endpoint cannot be reached, moving from name resolution to the application response. Check DNS first, then reachability and route, followed by HTTP headers and a verbose TLS/HTTP exchange.
Read the complete field guide →HOW THIS WORLD WAS BUILT
Source-linked commands, explicitly authored workflows.
The complete command library is public and each field guide explains prerequisites, failure modes, verification, and safety boundaries. Source-linked does not mean a command was executed on every platform.
Open the public command library →