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Chapter 49: Docker Containers: Lifecycle, docker run Flags, exec, logs, Restart Policies, Limits and Every Container Command: Cards

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Revision cards

Container lifecycle. You must know why a container is not running.
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Lesson: 49.1 Container lifecycle: created, running, paused, stopped, removed

Important docker run flags. Most of Docker is docker run with the right flags.
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Lesson: 49.2 docker run and its most important flags

exec, attach and logs. You need to look inside a live container.
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Lesson: 49.3 exec, attach and logs: get inside and read output

inspect, stats, top, port, diff, events. Facts beat guesses when debugging.
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Lesson: 49.4 inspect, stats, top, port, diff and events

Restart policies. Apps crash and servers reboot.
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Lesson: 49.5 Restart policies

CPU and memory limits. One leaky container can crash every other app.
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Lesson: 49.6 Resource limits: memory, CPU, pids and IO

cp, commit, rename, update, wait. Small daily jobs need small commands.
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Lesson: 49.7 cp, commit, rename, update, wait and export

Container logging drivers. Unlimited logs can fill a disk.
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Lesson: 49.8 Logging drivers and log rotation

Every docker container command. Quick recall saves time on call.
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Lesson: 49.9 Every docker container command: full reference

Interview cards

Explain the container lifecycle. create makes it, start runs PID 1, stop sends SIGTERM then SIGKILL after 10s, rm deletes it. run = create + start.
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Lesson: 49.1 Container lifecycle: created, running, paused, stopped, removed

Explain common docker run flags. -d background, --name, -p host:container, -e/--env-file, -v, --network, --restart, --rm, -it.
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Lesson: 49.2 docker run and its most important flags

exec vs attach? exec runs a new process (safe to exit). attach connects to PID 1; Ctrl+C can stop the container (detach with Ctrl+P Ctrl+Q).
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Lesson: 49.3 exec, attach and logs: get inside and read output

How do you check a container's IP and memory use? docker inspect -f with a Go template for the IP; docker stats --no-stream for CPU and memory.
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Lesson: 49.4 inspect, stats, top, port, diff and events

always vs unless-stopped? Both restart on crash and daemon start; unless-stopped stays down after you run docker stop, always comes back after a daemon restart.
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Lesson: 49.5 Restart policies

What happens when a container hits its memory limit? The kernel OOM-kills it (exit 137, OOMKilled=true). CPU limits only throttle, they do not kill.
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Lesson: 49.6 Resource limits: memory, CPU, pids and IO

Why not use docker commit in production? A committed image is not repeatable: no Dockerfile, hidden changes, hard to review. Use it only to save a debug state.
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Lesson: 49.7 cp, commit, rename, update, wait and export

How do you stop container logs filling the disk? Set --log-opt max-size=10m --log-opt max-file=3, or default it in daemon.json, or use the local driver.
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Lesson: 49.8 Logging drivers and log rotation

stop vs kill? stop sends SIGTERM and waits (default 10s) before SIGKILL; kill sends SIGKILL at once (or --signal).
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Lesson: 49.9 Every docker container command: full reference

Comparison cards

docker exec vs docker attach. exec: starts a new process inside.attach: joins the main process.
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Lesson: 49.3 exec, attach and logs: get inside and read output

docker stop vs docker kill. stop: SIGTERM, wait, then SIGKILL.kill: SIGKILL now.
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Lesson: 49.9 Every docker container command: full reference

always vs unless-stopped. always: restart every time.unless-stopped: restart unless you stopped it.
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Lesson: 49.5 Restart policies