Docker commands

Docker is a containerization platform that allows SDETs to create consistent, isolated test environments. It enables fast setup of test dependencies ( services, browsers), ensures reproducible test runs, simplifies CI/CD pipelines, and improves scalability of automated testing.

Getting Started

Create and run a container in background

docker run -d -p 80:80 docker/getting-started

• -d: Detached mode

• -p 80:80: Map port 80 on host to port 80 in container

• docker/getting-started: Image to use

Create and run a container in foreground

docker run -it -p 8001:8080 --name my-nginx nginx

• -it: Interactive mode with terminal

• -p 8001:8080: Map port 8001 on host to 8080 in container

• --name my-nginx: Name the container

• nginx: Image to use

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General Commands

Command	Description
docker ps	List running containers
docker ps -a	List all containers
docker ps -s	List running containers (with CPU/memory)
docker images	List all images
docker exec -it bash	Connect to container
docker logs	Show container logs
docker stop	Stop a container
docker restart	Restart a container
docker rm	Remove a container
docker port	Show port mappings
docker top	List running processes
docker killcker	Kill a container

<container> can be container ID or name.

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Docker Containers

Starting & Stopping

• Start: docker start my-nginx

• Stop: docker stop my-nginx

• Restart: docker restart my-nginx

• Pause: docker pause my-nginx

• Unpause: docker unpause my-nginx

• Kill: docker kill my-nginx

• Attach: docker attach my-nginx

• Wait (blocking): docker wait my-nginx

Information

• List running: docker ps

• List all: docker ps -a

• Logs: docker logs my-nginx

• Inspect: docker inspect my-nginx

• Events: docker events my-nginx

• Public Ports: docker port my-nginx

• Running processes: docker top my-nginx

• Stats (resources): docker stats my-nginx

• Changes: docker diff my-nginx

Creating

docker create [options] IMAGE

• -a, --attach: Attach stdout/err

• -i, --interactive: Attach stdin

• -t, --tty: Pseudo-tty

• --name NAME: Name the container

• -p, --publish 5000:5000: Port mapping

• --expose 5432: Expose a port

• -P, --publish-all: Publish all ports

• --link container:alias: Link containers

• -v, --volume $(pwd):/app: Mount a volume

• -e, --env NAME=hello: Set environment variables

Example:

docker create --name my_redis --expose 6379 redis:3.0.2

Manipulating

• Rename: docker rename old-name new-name

• Remove: docker rm my-nginx

• Update: docker update --cpu-shares 512 -m 300M my-nginx

Docker containers are lightweight, isolated environments that run applications and their dependencies. They share the host OS kernel but have their own filesystem, making them fast to start and efficient in resource usage. Containers provide consistency across development, testing, and production environments, simplifying deployment and scalability.

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Docker Images

Manipulating

• List images: docker images

• Remove image: docker rmi nginx

• Load image: docker load < ubuntu.tar.gz or docker load --input ubuntu.tar

• Save image: docker save busybox > ubuntu.tar

• Show history: docker history nginx

• Commit container: docker commit nginx

• Tag image: docker tag nginx user/nginx

• Push image: docker push user/nginx

Building Images

• Current directory: docker build .

• From GitHub: docker build github.com/creack/docker-firefox

• From Dockerfile via stdin: docker build - < Dockerfile

• From tar context: docker build - < context.tar.gz

• Tag build: docker build -t user/nginx .

• Custom Dockerfile: docker build -f MyDockerfile .

• From remote: curl example.com/Dockerfile | docker build -f - .

Docker images are read-only templates used to create Docker containers. They contain the application code, libraries, dependencies, and runtime environment needed for the application to run. Images can be pulled from Docker Hub or built locally from a Dockerfile. Once created, images are versioned, shared, and reused to ensure consistency across environments.

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Docker Networking

Manipulating Networks

• List networks: docker network ls

• Inspect network: docker network inspect MyOverlayNetwork

• Remove network: docker network rm MyOverlayNetwork

• Connect running container: docker network connect MyOverlayNetwork nginx

• Connect at start: docker run -it -d --network=MyOverlayNetwork nginx

• Disconnect: docker network disconnect MyOverlayNetwork nginx

Docker Networking allows containers to communicate with each other and with the outside world. It provides various network types such as bridge, host, and overlay, each suited for different use cases. Networking features include connecting containers, exposing ports, managing network security, and handling communication between containers in a multi-host setup.

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Docker Cleanup

Clean All

• Remove unused containers, volumes, networks: docker system prune

• Remove all unused images too: docker system prune -a

Containers

• Stop all containers: docker stop $(docker ps -a -q)

• Delete stopped containers: docker container prune

Images

• Remove dangling images: docker image prune

• Remove all unused images: docker image prune -a

Volumes

• List volumes: docker volume ls

• Prune unused volumes: docker volume prune

Docker volumes are used to persist data generated by and used by Docker containers. Unlike container filesystems, volumes are stored outside of containers, ensuring data remains intact even when containers are stopped or deleted. Volumes can be shared between containers, making them ideal for storing databases, configuration files, and logs.

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Miscellaneous

Docker Hub

• Search images: docker search nginx

• Pull image: docker pull user/image

• Login: docker login

• Push image: docker push user/image

Docker Hub is a cloud-based registry where users can store, share, and manage Docker images. It provides access to both public and private repositories, enabling easy distribution of containerized applications.

Batch Cleanup

• Stop all containers: docker stop -f $(docker ps -a -q)

• Remove all containers: docker rm -f $(docker ps -a -q)

• Remove all images: docker rmi -f $(docker images -q)