# Docker CLI

## The commands you'll use constantly

Module 2 introduced pull/run/stop/rm conceptually. This module adds the rest of the everyday
toolkit — and every one of them maps directly to a Linux concept you already have from ROOT 01.

## `docker ps` — what's running right now

```
$ docker ps
CONTAINER ID   IMAGE          STATUS         NAMES
a1b2c3d4e5f6   nginx:alpine   Up 2 minutes   web
```

This is the container-level equivalent of ROOT 02's `ps aux` — "what's actually running." Add
`-a` to see stopped containers too, not just running ones.

## `docker logs` — what has it been saying?

```
$ docker logs web
```

The container-level equivalent of reading a service's log file from ROOT 02 — except Docker
captures a container's stdout/stderr automatically, so there's no config needed to find WHERE
the logs live, unlike a traditional service.

## `docker exec` — run a NEW command inside an ALREADY-running container

```
$ docker exec web sh -c 'cat /etc/nginx/nginx.conf'
```

Different from `docker run`, which creates a brand-new container — `exec` reaches INTO an
existing, running one, exactly like ROOT 01's `ps`/inspection commands but scoped to one
specific container's process namespace.

## `docker inspect` — the full, detailed truth about a container

```
$ docker inspect web --format '{{.State.Running}}'
true
```

Returns a large JSON document with everything Docker knows about a container — `--format` lets
you extract just the one field you care about, rather than reading the whole thing.

## `docker stop` vs `docker rm`

`docker stop` gracefully stops a running container (sends SIGTERM, then SIGKILL after a grace
period — literally ROOT 01's process-signals lesson, applied to a container's main process).
`docker rm` deletes a STOPPED container entirely — `docker rm -f` combines both (force-stop then
remove) in one step.

## Instructor Notes

**Lesson goal:** Explicitly map every Docker CLI command back to the equivalent ROOT 01/02
Linux concept students already have — this is a translation exercise, not new material.

**Approximate timing:** 15 minutes read; 10 minutes live.

**Common misconception to watch for:** confusing `docker run` (creates a new container) with
`docker exec` (runs a command in an existing one) — a very common early mixup.

**Demo idea:** run `docker exec` against a container, then immediately `docker run` the same
image again, and compare `docker ps` before/after to show the difference concretely.