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ced4568andClaude Sonnet 5 e007bcf000 feat(root02): author Linux Administration & Networking

Adds all 6 ROOT 02 modules (Linux system administration, storage & filesystems, the
Networking Mental Model, Linux network inspection, DNS & HTTP, Linux troubleshooting) — 37
activities, each with a real lesson, demonstration/guided exercise, knowledge check, hands-on
Lab, and reflection. The Networking Mental Model module (M3) gets deliberately extra depth per
its "critical module" designation, with no lab by design — conceptual mastery via knowledge
check and guided exercise, matching root-05-m00's own precedent.

Adds 6 new hands-on Linux/networking scenarios plus 2 MCQs: linux-service-inspection (inspects
the platform's own real nginx without touching it — a genuinely safe, real service-inspection
target that avoids ever risking the Lab's own connectivity), linux-service-lifecycle (start/
verify/stop a fully controllable service), linux-storage-inspection, linux-network-inspection
(ip/ss/getent/curl, each framed as answering one specific diagnostic question),
linux-dns-http-diagnosis (a genuine DNS-resolves-but-wrong-port failure, diagnosed and fixed),
and linux-troubleshooting-framework (a real missing-config-file failure, resolved via the
RootNode Observe/Evidence/Hypothesis/Test/Repair/Validate/Prevent framework). All tested
end-to-end via the real scenario-validation API, including negative tests confirming they fail
when unsolved.

Wires rootnode-linux-networking-assessment (2 required + 4 random-draw scenarios) using the
existing Phase 3B assessment engine.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

2026-08-26 17:07:46 -05:00

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Demonstration: Two Different Questions, Two Different Commands

OBSERVE

$ df -h /
Filesystem  Size  Used  Avail  Use%  Mounted on
overlay     937G  199G   691G   23%  /

The root filesystem overall: 23% used, plenty free.

HYPOTHESIS

Predict: does this tell you anything about which specific directory is using the most space?

INSPECT

$ du -sh /var/log/* 2>/dev/null
1.2M  /var/log/nginx
850K  /var/log/k3s.log

No — df only ever answers "how full is this filesystem overall." Finding a SPECIFIC large consumer requires du, pointed at the directories you suspect.

CHANGE

Narrow further into a single suspicious directory:

$ du -sh /var/log/nginx/*
600K  /var/log/nginx/access.log
600K  /var/log/nginx/error.log

VERIFY

You now know both the overall filesystem picture (df) AND exactly which files are contributing to it (du, narrowed progressively) — two genuinely different tools for two genuinely different questions, not interchangeable.

Instructor Notes

Demo goal: Make the df/du distinction concrete by actually needing BOTH to answer a realistic "what's using my disk" question.

Approximate timing: 8 minutes live.

Common mistake to watch for: running du -sh / directly (extremely slow on a large filesystem, since it recurses everything) instead of narrowing progressively into suspected directories first.

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