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]>
39 lines
2.6 KiB
JSON
39 lines
2.6 KiB
JSON
{
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"id": "docker-container-networking",
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"title": "It Works Inside the Container, But Not From the Host — Why?",
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"category": "Containers",
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"isolation_type": "shared_namespace",
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"difficulty": "Medium",
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"type": "task",
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"weight": 6,
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"description": "## It Works Inside the Container, But Not From the Host — Why?\n\nA container named `net-lab-web` is already running `nginx:alpine`. It works perfectly INSIDE itself, but `curl http://localhost:8099/` from this Lab's own shell fails.\n\n**Your task:**\n\n1. Confirm the app really does work internally: `docker exec net-lab-web wget -qO- http://localhost:80/`\n2. Confirm `curl http://localhost:8099/` from the host really does fail\n3. Diagnose why (hint: `docker port net-lab-web` shows what ports are actually published — or aren't)\n4. Fix it: remove the container and recreate it WITH the correct port publish flag, so `curl http://localhost:8099/` succeeds",
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"hints": [
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{
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"title": "Checking what's actually published",
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"body": "`docker port <container>` lists every host-port-to-container-port mapping currently configured — an empty result means NOTHING is published, no matter how well the app works internally.",
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"command": "docker port net-lab-web"
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},
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{
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"title": "The fix — port publishing can't be added to a running container",
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"body": "Port publishing is set at container CREATION time, not changeable afterward — you must remove and recreate it with `-p hostPort:containerPort`.",
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"command": "docker rm -f net-lab-web\ndocker run -d --name net-lab-web -p 8099:80 nginx:alpine"
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}
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],
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"setup_commands": [
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{ "command": "docker rm -f net-lab-web 2>/dev/null; true" },
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{ "command": "docker pull nginx:alpine" },
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{ "command": "docker run -d --name net-lab-web nginx:alpine" }
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],
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"validation": {
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"commands": [
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{ "description": "net-lab-web is running from the correct image", "command": "docker inspect net-lab-web --format '{{.Config.Image}} {{.State.Running}}' 2>/dev/null", "expected_output": "nginx:alpine true", "match": "exact" },
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{ "description": "port 8099 is now genuinely published to the container's port 80", "command": "docker port net-lab-web 2>/dev/null | grep 80/tcp", "expected_output": "8099", "match": "contains" },
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{ "description": "the published port is actually reachable from the host", "command": "curl -sf http://localhost:8099/ -o /dev/null -w '%{http_code}'", "expected_output": "200", "match": "exact" }
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]
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},
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"default_namespace": "default",
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"teardown_commands": [
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{ "command": "docker rm -f net-lab-web 2>/dev/null" }
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]
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}
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