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Docker Containers

6. Docker Containers

🚀 What is a Container (Running)?

If an image is a recipe, then a container is the cooked meal.

A container is a running instance of an image. You can run multiple containers from the same image, just like cooking the same recipe multiple times.

🕹️ Core Container Commands

# === CREATING AND RUNNING ===

# Run a container (creates + starts)
docker run nginx

# Run with a custom name
docker run --name my-nginx nginx

# Run in detached mode (background)
docker run -d nginx

# Run interactively (with terminal)
docker run -it ubuntu bash

# Run and auto-remove when stopped
docker run --rm nginx

# === LISTING CONTAINERS ===

# List running containers
docker ps

# List ALL containers (including stopped)
docker ps -a
docker ps --all

# === STARTING / STOPPING ===

# Stop a running container
docker stop my-nginx

# Start a stopped container
docker start my-nginx

# Restart a container
docker restart my-nginx

# Pause a container
docker pause my-nginx

# Unpause a container
docker unpause my-nginx

# === REMOVING ===

# Remove a stopped container
docker rm my-nginx

# Force remove a running container
docker rm -f my-nginx

# Remove all stopped containers
docker container prune

# === INSPECTING ===

# View container details
docker inspect my-nginx

# View running processes inside container
docker top my-nginx

🔍 Understanding `docker ps` Output

docker ps

CONTAINER ID   IMAGE    COMMAND                  CREATED         STATUS         PORTS                  NAMES
a3f5b2c1d4e8   nginx    "/docker-entrypoint.…"   2 minutes ago   Up 2 minutes   0.0.0.0:80->80/tcp     my-nginx

Column	Meaning
CONTAINER ID	Unique short ID of the container
IMAGE	Image used to create the container
COMMAND	Process running inside the container
CREATED	When the container was created
STATUS	Current state (Up, Exited, Paused)
PORTS	Port mappings (host:container)
NAMES	Human-readable name

🔄 Container Lifecycle Example

# 1. Create and run nginx
docker run -d --name web nginx

# 2. Check it's running
docker ps

# 3. Stop it
docker stop web

# 4. See it in stopped state
docker ps -a

# 5. Start it again
docker start web

# 6. Remove it (must be stopped first)
docker stop web
docker rm web

# Or force remove while running
docker rm -f web

⚠️ Common Container Mistakes

Forgetting -d and blocking your terminal
Running docker rm on a running container without -f
Accumulating stopped containers — always clean up with docker container prune