The docker run instruction is the quickest way to spin up a new container from an image. For instance, to print a greeting and exit:

docker run debian:11-slim /bin/echo "Hello container"

The command above instructs Docker to:

• Locate the debian:11-slim image locally; if missing, pull it from Docker Hub.
• Create a transient container from that image.
• Execute /bin/echo "Hello container" inside the container.
• Terminate the container once the command finishes.

Interactive Shell Inside a Container

To open an interactive terminal:

docker run -it --name demo-shell debian:11-slim bash

Flags explained:

• -i keeps STDIN open so you can type commands.
• -t allocates a pseudo-TTY, giving you a shell prompt.
• --name demo-shell assigns a human-readable identifier to the container.

Running a Detached Container

For long-lived services, detach the container from your terminal:

docker run -d --name looper alpine:latest \
  sh -c 'while true; do echo "$(date) loop"; sleep 2; done'

The output is a unique container ID, e.g.:

3f4e8a1b9c2d7f0a9e5c8b2d4f6a1e3b5c7d9e0f2a4b6c8d0e2f4a6b8c0d2e

Inspecting Running Containers

docker ps

Typical output:

CONTAINER ID   IMAGE           COMMAND                  CREATED          STATUS          PORTS     NAMES
3f4e8a1b9c2d   alpine:latest   "sh -c 'while true; …"   30 seconds ago   Up 29 seconds             looper

Essential Container Operations

# Start a stopped container
docker start looper

# Gracefully stop
docker stop looper

# Force restart
docker restart looper

# Remove (must be stopped first)
docker rm looper

Connnecting to a Running Container

Two common approaches:

1. docker attach looper — attaches you're terminal to the main process; exiting will stop the container.
2. docker exec -it looper sh — spawns a new shell process; exiting leaves the container running.

Image Management

# List local images
docker images

# Download an image
docker pull nginx:1.25-alpine

# Search Docker Hub
docker search redis

# Delete an image
docker rmi debian:10-slim

# Persist container changes as a new image
docker commit looper my-alpine-looper:1.0

Lifecycle Cheat Sheet

# View all containers (including exited)
docker ps -a

# Quick cleanup: stop and remove all stopped containers
docker container prune -f