ced4568andClaude Sonnet 5
682ef2de47
Adds all 8 ROOT 04 modules (why containers exist, images & containers, Docker CLI, container networking, container storage, Dockerfile & image build, Docker Compose, containers → Kubernetes) — 43 activities, using the nested Docker Engine Phase 6D built and tested. Modules 1, 2, and 8 are conceptual (no lab by design) — the honest bridge module (M8) explicitly names what Kubernetes adds beyond what this course already taught, without re-teaching Kubernetes itself. Adds 5 new hands-on Docker scenarios plus 2 MCQs, all against the real nested Docker Engine: docker-cli-basics (run/exec/inspect a real container), docker-container-networking (a genuine "works internally, unreachable from host" port-publishing failure, diagnosed and fixed by recreating the container with the correct `-p` flag), docker-container-storage (a real destroy/recreate cycle proving named-volume persistence, not just described), docker-build-image (a real Dockerfile, a real build, a real custom image run), and docker-compose-multiservice (a real two-service Compose application with a real published port). All tested end-to-end via the real scenario-validation API, including negative tests. Wires rootnode-containers-assessment (2 required + 4 random-draw scenarios) using the existing Phase 3B assessment engine. This completes the entire ROOT_ Foundations sequence (ROOT 01-04) — see docs/PHASE6E_ROOT_FOUNDATIONS_COMPLETION.md. Co-Authored-By: Claude Sonnet 5 <[email protected]>
41 lines
1.3 KiB
Markdown
41 lines
1.3 KiB
Markdown
# Knowledge Check: Container Networking
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---
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**1. A container works fine when tested with `docker exec <container> curl localhost:80`, but
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`curl http://localhost:8080/` from the host fails. What's the most likely cause?**
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*Answer:* The container was never started with a port-publish flag (`-p 8080:80`) mapping the
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host port to the container's port — the app works internally, but nothing connects the host to
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it.
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---
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**2. Can you add port publishing to an already-running container?**
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*Answer:* No — port publishing is set at container creation time; you must remove and recreate
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the container with the correct `-p` flag.
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---
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**3. How can one container reach another by name instead of IP?**
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*Answer:* If both containers are on the same user-defined Docker network, Docker's built-in DNS
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resolves the target container's NAME automatically — no IP address needed.
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---
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**4. Why does container-name resolution fail between two containers that AREN'T on the same
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Docker network?**
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*Answer:* Docker's per-network DNS only knows about containers actually attached to that
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specific network — being on a different (or no) network means there's no DNS entry for the
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target container at all.
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## Instructor Notes
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**Facilitation:** Question 1 directly previews this module's Lab — a good moment to build
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anticipation for it.
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**Approximate timing:** 5 minutes.
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