{
  "id": "docker-cli-basics",
  "title": "Run, Exec Into, and Inspect a Real Container",
  "category": "Containers",
  "isolation_type": "shared_namespace",
  "difficulty": "Easy",
  "type": "task",
  "weight": 5,
  "description": "## Run, Exec Into, and Inspect a Real Container\n\n**Your task:**\n\n1. Run a container named `cli-lab-app` from the `nginx:alpine` image, in the background (detached)\n2. Use `docker exec` to run a command INSIDE the running container that creates `/tmp/marker.txt` containing exactly `hello-from-exec`\n3. Record the running container's ID to `/srv/docker-cli-lab/container-id.txt`\n4. Use `docker logs` and `docker inspect` to confirm it's actually running — you don't need to write those findings anywhere, just use them to verify your own work",
  "hints": [
    {
      "title": "Running and execing",
      "body": "`docker run -d --name <name> <image>` starts a container in the background under a name you choose instead of a random one. `docker exec <name> <command>` runs a NEW command inside an ALREADY-running container — different from `docker run`, which starts a brand new container.",
      "command": "docker run -d --name cli-lab-app nginx:alpine\ndocker exec cli-lab-app sh -c 'echo hello-from-exec > /tmp/marker.txt'"
    },
    {
      "title": "Recording the container ID",
      "body": "`docker ps -q -f name=<name>` prints just the ID of a container matching that name filter.",
      "command": "mkdir -p /srv/docker-cli-lab\ndocker ps -q -f name=cli-lab-app > /srv/docker-cli-lab/container-id.txt"
    }
  ],
  "setup_commands": [
    { "command": "mkdir -p /srv/docker-cli-lab" },
    { "command": "docker rm -f cli-lab-app 2>/dev/null; true" },
    { "command": "docker pull nginx:alpine" }
  ],
  "validation": {
    "commands": [
      { "description": "cli-lab-app is running from the correct image", "command": "docker inspect cli-lab-app --format '{{.Config.Image}} {{.State.Running}}' 2>/dev/null", "expected_output": "nginx:alpine true", "match": "exact" },
      { "description": "the marker file was actually created inside the container via exec", "command": "docker exec cli-lab-app cat /tmp/marker.txt 2>/dev/null", "expected_output": "hello-from-exec", "match": "exact" },
      { "description": "the container ID was correctly recorded and matches the real running container", "command": "[ \"$(cat /srv/docker-cli-lab/container-id.txt 2>/dev/null)\" = \"$(docker ps -q -f name=cli-lab-app)\" ] && echo match || echo mismatch", "expected_output": "match", "match": "exact" }
    ]
  },
  "default_namespace": "default",
  "teardown_commands": [
    { "command": "docker rm -f cli-lab-app 2>/dev/null; rm -rf /srv/docker-cli-lab" }
  ]
}