docker version
Purpose
Verifies that the Docker CLI is installed and whether it can communicate with the Docker daemon.
What it shows
Client version information and server (daemon) version information.
Usage
docker version
Notes
If the Docker daemon is not running, only client information is shown and the server section fails.
docker info
Purpose
Displays detailed system-wide Docker configuration and runtime information.
What it shows
Docker root directory, storage driver, number of images and containers, OS and architecture details.
Usage
docker info
docker run
Purpose
Creates and starts a new container from an image.
Common usage
docker run hello-world
docker run -it ubuntu bash
docker run -d –name my-nginx -p 8080:80 nginx
Key options
-it runs the container interactively
-d runs the container in the background
–name assigns a readable name to the container
-p maps host ports to container ports
docker ps
Purpose
Lists containers.
Usage
docker ps
docker ps -a
docker ps shows running containers only.
docker ps -a includes stopped containers.
docker stop and docker start
Purpose
Stops or starts an existing container.
Usage
docker stop my-container
docker start my-container
docker rm
Purpose
Removes a stopped container.
Usage
docker rm my-container
docker inspect
Purpose
Displays low-level JSON metadata for containers or images.
Typical use cases
Inspect environment variables, network settings, mounts, ports, and runtime configuration.
Usage
docker inspect my-container
docker exec
Purpose
Runs a command inside a running container.
Interactive shell
docker exec -it my-container bash
docker exec -it my-container sh
One-off command
docker exec my-container ls /etc
docker logs
Purpose
Displays standard output and error logs from a container.
Usage
docker logs my-container
docker logs -f my-container
docker logs –tail 50 my-container
docker stats
Purpose
Shows real-time CPU, memory, network, and disk usage for containers.
Usage
docker stats
docker stats my-container
docker pull
Purpose
Downloads an image from a container registry.
Usage
docker pull ubuntu
docker pull nvcr.io/nvidia/pytorch:24.04-py3
docker images
Purpose
Lists all locally available images.
Usage
docker images
docker tag
Purpose
Creates an additional name and tag for an image, commonly used before pushing to a registry.
Usage
docker tag nginx myuser/nginx:demo
docker push
Purpose
Uploads an image to a container registry.
Usage
docker push myuser/nginx:demo
Prerequisite
You must authenticate with the registry using docker login.
docker system df
Purpose
Displays Docker disk usage information.
Usage
docker system df
docker container prune
Purpose
Removes all stopped containers.
Usage
docker container prune
docker image prune
Purpose
Removes dangling and unused images.
Usage
docker image prune
docker system prune
Purpose
Removes unused containers, networks, images, and build cache.
Usage
docker system prune
Aggressive cleanup
docker system prune -a –volumes
This removes all unused images and volumes and should be used with caution.
docker context ls
Purpose
Lists available Docker contexts such as local, desktop, or remote environments.
Usage
docker context ls
docker context use
Purpose
Switches the active Docker context.
Usage
docker context use desktop-linux
Default bridge network
Purpose
Provides a private, NATed network for containers. Containers attached to the same bridge network can communicate using IP addresses. Name-based DNS resolution is limited on the default bridge.
Notes
This is the network used when no –network flag is specified.
Inspect the default bridge
docker network inspect bridge
Run a container on the default bridge
docker run –rm alpine sh
Host network
Purpose
Shares the host network stack with the container.
Notes
On macOS, Docker runs inside a virtual machine. As a result, –network host does not behave the same way it does on Linux and does not give direct access to the Mac’s network namespace.
Run a container with host networking
docker run –rm –network host alpine sh
None network
Purpose
Disables all networking for the container except the loopback interface.
Run a container with no networking
docker run –rm –network none alpine sh
docker network ls
Purpose
Lists all Docker networks.
Usage
docker network ls
docker network inspect
Purpose
Displays detailed configuration and connected containers for a network.
Usage
docker network inspect ai-net
docker network create
Purpose
Creates a user-defined bridge network with built-in DNS resolution and isolation.
Usage
docker network create ai-net
Notes
User-defined bridge networks are recommended for multi-container applications.
docker network rm
Purpose
Deletes a Docker network.
Usage
docker network rm ai-net
Run container on a specific network
Purpose
Attaches a container to a specified network at startup.
Usage
docker run -d –name web –network ai-net nginx
docker network connect
Purpose
Connects an existing container to an additional network.
Usage
docker network connect other-net web
Notes
Containers can be attached to multiple networks simultaneously.
Container DNS Resolution
Purpose
Allows containers on the same user-defined bridge network to resolve each other by name using Docker’s embedded DNS server.
Test DNS resolution
docker run –rm -it –network ai-net alpine sh -c “apk add –no-cache bind-tools && nslookup web”
Inspect DNS configuration inside a container
docker exec -it web cat /etc/resolv.conf
Add a network alias
docker network connect –alias websvc ai-net web
Port Publishing and Exposure
-p flag
Purpose
Publishes a container port to the host, enabling host-to-container communication.
Syntax
-p <host_port>:<container_port>
Example
docker run -d –name web -p 8080:80 nginx
Verify published ports
docker ps
docker port web
Notes
Port publishing is not required for container-to-container communication on the same Docker network.
Same network communication
Purpose
Allows containers on the same network to communicate without published ports.
Test connectivity
docker run –rm -it –network ai-net nicolaka/netshoot sh -c “curl -I http://web”
Cross-network isolation
Purpose
Demonstrates that containers on different networks cannot communicate by default.
Test isolation
docker run –rm -it –network other-net nicolaka/netshoot sh -c “curl -I http://web || echo 'unreachable'”
Connect container to multiple networks
docker network connect other-net web
Re-test connectivity
docker run –rm -it –network other-net nicolaka/netshoot sh -c “curl -I http://web”
Inspect container network settings
Purpose
Displays IP addresses, networks, and endpoints for a container.
Usage
docker inspect web
Use a diagnostic container
Purpose
Provides networking tools such as curl, ping, nslookup, and traceroute.
Usage
docker run –rm -it –network ai-net nicolaka/netshoot
Remove containers
docker rm -f web client
Remove networks
docker network rm ai-net test-net other-net
Concept Summary
Named volume
Bind mount
tmpfs
Named volume example
Create a named volume:
docker volume create myvol
docker volume ls
docker volume inspect myvol
Run a container using the volume:
docker run –rm -it -v myvol:/data alpine sh
Inside the container:
echo “hello from volume” > /data/file.txt
ls /data
exit
Run another container with the same volume:
docker run –rm -it -v myvol:/data alpine sh
Inside:
cat /data/file.txt
exit
What this demonstrates
Bind mount example (host directory)
Create a directory on the host:
mkdir -p ~/docker-bind-test
echo “hello from host” > ~/docker-bind-test/host.txt
Run a container with a bind mount:
docker run –rm -it \
-v ~/docker-bind-test:/data \
alpine sh
Inside the container:
ls /data
echo “written from container” > /data/container.txt
exit
On the host:
ls ~/docker-bind-test
cat ~/docker-bind-test/container.txt
What this demonstrates
tmpfs example (in-memory)
Run a container with tmpfs:
docker run –rm -it \
–tmpfs /data:rw,size=64m \
alpine sh
Inside:
echo “temp data” > /data/tmp.txt
ls /data
exit
Run a new container:
docker run –rm -it –tmpfs /data alpine sh -c “ls /data || echo empty”
What this demonstrates
Create and list volumes
docker volume create ai-data
docker volume ls
Inspect volume metadata
docker volume inspect ai-data
Look for:
Use a volume and verify persistence
Write data into the volume:
docker run –rm -it -v ai-data:/models alpine sh
Inside:
echo “model checkpoint v1” > /models/checkpoint.txt
exit
Verify persistence:
docker run –rm -it -v ai-data:/models alpine sh -c “cat /models/checkpoint.txt”
What this demonstrates
Create a simple development file
On the host:
mkdir -p ~/bind-dev
cat > ~/bind-dev/app.py « 'EOF'
print(“version 1”)
EOF
Run a Python container with bind mount:
docker run –rm -it \
-v ~/bind-dev:/app \
python:3.12-slim \
python /app/app.py
Edit the file on the host:
echo 'print(“version 2”)' » ~/bind-dev/app.py
Re-run the container:
docker run –rm -it \
-v ~/bind-dev:/app \
python:3.12-slim \
python /app/app.py
What this demonstrates
Create a shared volume
docker volume create shared-vol
Writer container
Run:
docker run –rm -it -v shared-vol:/shared alpine sh
Inside:
echo “written by writer” > /shared/data.txt
exit
Reader container
Run:
docker run –rm -it -v shared-vol:/shared alpine sh
Inside:
cat /shared/data.txt
exit
What this demonstrates
Back up a volume to a tar archive
Create a backup:
docker run –rm \
-v ai-data:/data \
-v $(pwd):/backup \
alpine \
tar czf /backup/ai-data-backup.tar.gz -C /data .
Verify:
ls ai-data-backup.tar.gz
What this does
Simulate data loss
Delete and recreate the volume:
docker volume rm ai-data
docker volume create ai-data
Check it is empty:
docker run –rm -it -v ai-data:/models alpine sh -c “ls /models”
Restore from backup
Restore the data:
docker run –rm \
-v ai-data:/data \
-v $(pwd):/backup \
alpine \
tar xzf /backup/ai-data-backup.tar.gz -C /data
Verify:
docker run –rm -it -v ai-data:/models alpine sh -c “cat /models/checkpoint.txt”
What this demonstrates
List volumes
docker volume ls
Remove specific volumes
docker volume rm myvol shared-vol ai-data
Remove all unused volumes
docker volume prune
Inspect disk usage
docker system df -v
What this demonstrates
This reference documents the core Docker Compose commands used to:
All commands assume:
mkdir and cd
Purpose
Creates and enters a new project directory for a Compose application.
Usage
mkdir compose-lab && cd compose-lab
mkdir app
What it does
docker compose up
Purpose
Builds images (if needed) and starts all services defined in docker-compose.yml.
Usage
docker compose up
docker compose up -d
docker compose up -d –build
Options
What it does
When to use
docker compose down
Purpose
Stops and removes all services in the Compose project.
Usage
docker compose down
docker compose down -v
docker compose down –rmi local -v
Options
What it does
When to use
docker compose ps
Purpose
Lists the current status of services in the Compose project.
Usage
docker compose ps
What it does
When to use
docker compose logs
Purpose
Displays logs from all services in the project.
Usage
docker compose logs
docker compose logs -f
docker compose logs api
Options
What it does
When to use
docker compose build
Purpose
Builds images for services that specify a build: section.
Usage
docker compose build
docker compose build api
What it does
When to use
docker compose exec
Purpose
Runs a command inside a running service container.
Usage
docker compose exec api sh
docker compose exec db psql -U composeuser compose_db
What it does
When to use
docker compose stop
Purpose
Stops services without removing containers.
Usage
docker compose stop
docker compose stop db
What it does
When to use
docker compose start
Purpose
Restarts stopped services.
Usage
docker compose start
docker compose start db
What it does
When to use
docker inspect
Purpose
Displays low-level metadata about a container.
Usage
docker inspect compose-db
docker inspect compose-api
What it does
When to use
docker compose exec env
Purpose
Displays environment variables inside a container.
Usage
docker compose exec api env | sort
What it does
When to use
docker compose up –scale
Purpose
Runs multiple instances of a service.
Usage
docker compose up -d –scale api=3
What it does
When to use
Important limitation
Compose does not automatically load-balance traffic across replicas.
A reverse proxy (nginx, Traefik) is required for real traffic distribution.
curl http://localhost:8080
Purpose
Tests connectivity from the host into a containerized service.
Usage
curl http://localhost:8080/healthz
curl http://localhost:8080/readyz
What it does
When to use
docker compose down -v
Purpose
Destroys the entire Compose environment including volumes.
Usage
docker compose down -v
What it does
When to use
docker compose down –rmi local -v
Purpose
Removes everything created by Compose including images.
Usage
docker compose down –rmi local -v
What it does
When to use