Docker + Docker Compose

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Commands

Docker

docker pull <image>: Pull Image from Docker Hub
docker create <image>: Create a container from an Image
docker start <container_name/container_id>: Start a container
docker stop <container_name/container_id>: Stop a container
docker kill <container_name/container_id>: Kill the entrypoint process of the container
docker rm <container_name/container_id>: Remove a container
docker ps: Get all running containers
docker ps -a: Get all containers
docker stop $(docker ps -a -q): Stop all containers
docker rm $(docker ps -a -q): Remove all containers
docker image rm $(docker image ls -q): Remove all images
docker run --name <container_name> -p <host_port>:<container_port> <image>: Pull, create, start and run a container
docker run -d <image>: Run in detached mode
docker run -e <key>=<value> <image>: Run with environment variable
docker run -it <image> <command>: Run a container and overwrite the default command
docker run -it --entrypoint <entrypoint_command> <image>: Run a container and overwrite the default entrypoint
docker inspect <container_name>: Get details about the container
docker exec -it <image_name> <command>: Execute a command in a running container with interactive mode
docker -v <volume_name>:<path_in_container> <image>: Bind path in the container to a Docker volume
docker -v <path_in_host>:<path_in_container> <image>: Bind path in the container to another path in the host
docker volume ls: List all volumes
docker volume create <volume_name>: Create a Docker volume
docker network create <network_name>: Create a user-defined network
docker run --network=<network_name> <image>: Run a docker container in a certain network
docker run --link=<container> <image>: Run a docker container and link network it with another container (legacy)
docker build <path>: Build docker image
docker build --tag <image_name> <path>: Build docker image with a tag
docker build --platform linux/amd64 <path>: Build for a specific target platform. This is used when building on M1 Macbook but target is linux.
docker build - < <custom_path>: Build docker image when the name is not Dockerfile
docker tag <image_name> <company>/<new_image_name>:<version>: Add a Docker Repository tag to an image. It can be also used for adding more tags
docker login: Log into a Docker Repository
docker push <company>/<new_image_name>:<version>: Push to a Docker repository, ex: DockerHub
docker commit <container_name/container_id> <image>: Create an image from a running container
docker logs -f --tail <lines_count> <container_name>: Print number of lines of the container logs and keep streaming
docker stats: Show live streaming of the containers’ resource usage

Docker Compose

docker compose build: Build services of the docker compose
docker compose build <service>: Build a service of the docker compose
docker compose create: create services
docker compose start: start services
docker compose run: Run a command in a services
docker compose restart: Restart services
docker compose restart <service>: Restart a service
docker compose pause: Pause services
docker compose unpause: Unpause services
docker compose stop: Stop services
docker compose rm: Remove stopped containers
docker compose up: Create and start containers
docker compose pull: Pull all services’ images. It’s good when updating services images
docker compose up -d: Create and start containers in detached mode
docker compose up -d <service>: Create and start containers in detached mode for a certain service
docker compose up --scale <service>=<count>: Create and start containers and scale the number of a service
docker compose down: Stop and remove containers
docker compose logs -f --tail <lines_count>: Print the logs for all services. -f means follow and --tail is the number of lines.
docker compose logs -f --tail <lines_count> <service>: Print the logs for a certain services
docker compose up -d && docker compose logs -f: This will start the container and then show the logs. On exit, it will still keep docker containers running.

DockerFile

FROM <image>: Based image
FROM <image> as <stage>: Based image, also assign name to be used for multi-stage image building
RUN <command>: Runs a certain command inside the image
Expose <port>/<protocol>: Used for documentation purposes to available ports
COPY <source> <destination>: Copys file from host to image
COPY --from=<stage> <source> <destination>: Copys file from host to image. Cross stage copy.
ADD <source> <destination>: Similar to COPY but can also download and extract tar files
ENV <key>=<value>: Define an environment variables
USER <user>:<group>: Used to define a user to run the commands
WORKDIR <destination>: Set working directory to avoid many cd
CMD <command> <param1> ... or CMD ["<command>", "<param1>"]: The default command to run for the container
ENTRYPOINT <command> <param1> ... or ENTRYPOINT ["<command>", "<param1>"]: The required command to run for the container.

Docker Compose File

services: Array of services to start
- image: Docker image name
- build: Path to a Dockerfile
- port: Array of exposed ports
- environment: Array of environment variables
- volumes: mapping of volumes
- networks: Define used network
- restart: Restart policy for the container. no, on-failure, always, unless-stopped
networks: Defines available networks

When merging two docker compose files, there are ways to override definitions:

Use profile, to run services for a certain profile passed to docker compose command
Use !reset <type>, to remove a property. <type> can be null or []
USe !override, to completely replace a property with another

Questions?

ADD vs COPY?

They both have similar functionality but ADD can also extract tar file and also download from the network
CMD vs ENTRYPOINT?

They both execute commands. Use CMD when you want the user of your image to have the flexibility to run whichever executable they choose when starting the container. Use ENTRYPOINT when you want the container to behave exclusively as if it were the executable it’s wrapping.

We can combine both of them and use ENTRYPOINT when we need a command to always run when the container starts and CMD to pass the parameters. We can then allow our users to overwrite the paramters when using docker run.

expose vs port?
- expose is used for documentation purposes to available ports. It does not expose the port to the host machine.
- port is used to map the port from the host machine to the container.

Diagrams

Source: Docker Docs

Source: Docker Internals

Interesting Docker Images

jwilder/docker-gen - Generate files from docker container meta-data
jwilder/nginx-proxy - Automated Nginx reverse proxy for docker containers. It has both nginx and docker-gen. It also can be pulled as nginxproxy/nginx-proxy but they are essentially the same thing.
nginxproxy/acme-companion - Automated ACME SSL certificate generator for nginx-proxy container.
ghcr.io/letsencrypt/pebble - An ACME test server, useful to test against a Let’s Encrypt server.