This repository contains several tutorials and notes on how to use Docker. It is recommended to go through the tutorials, while using the README.md as reference material.
Main Reference Material: DOCKER, FROM scratch by Aaron Powell
Would like to give a shout out to Aaron Powell. I used several difference sources to make this guide (Stack Overflow / Official Documentation), but his tech talk presented the ideal flow on how to learn Docker from a beginner point of view. Would highly recommend watching his talk (Main Reference Material). Here is their GitHub: https://github.com/aaronpowell
Docker is...
- Containers (Not a virtual machine)
- Usable in Linux, Mac OS, and Windows
- https://stackoverflow.com/questions/28089344/docker-what-is-it-and-what-is-the-purpose
An Image is...
- Your starting point
- What you produce as an output
- A class definition
A Container is...
- A running image
- A running implementation of a class definition (See above: Image)
A Host is...
- The machine docker is installed on
A DockerFile is...
- An instruct set (Domain-specific-language), on how to create an image in docker. Used to create an image, which can be run as a container later on
docker-compose is...
- Is a file called docker-compose.yml
- Describes an environment we can use to run docker
- "...A tool for defining and running multi-container Docker applications." - https://docs.docker.com/compose/overview/
An example Docker command: docker run -it --rm ubuntu /bin/bash
- cli: docker
- command: run
- options: -it --rm
- arguments (first is image, second is executable): ubuntu /bin/bash
docker ps
Lists the containers running on the machine
exit
When executed within a container, exits the container, and returns to host's terminal
docker ps -a
or
docker ps --all
Lists all containers, regardless of status (example: running or stopped)
docker start INSERT_CONTAINER_NAME_OR_ID
Starts the container with id. Can use either partial CONTAINER ID or the full NAMES
docker stop INSERT_CONTAINER_NAME_OR_ID
Stop the container with that id. Can use either partial CONTAINER ID or the full NAMES. This will stop a container gracefully (proper cleanup of database connections). Not a hard 'pull the power' stop
docker rm INSERT_CONTAINER_NAME_OR_ID
Removes the container. Can use either partial CONTAINER ID or the full NAMES
-it
- -i keeps STDIN open even if not attached
- -t Allocate a pseudo-tty
-it allows you to use a terminal to interact with a running Docker container.
Examples:
- Start new container with bash:
docker run -it ubuntu /bin/bash - View running container with bash):
docker exec -it INSERT_CONTAINER_NAME_OR_ID bash
For reference, see https://docs.docker.com/engine/reference/run/
-d
Starts container in detached mode.
-w
Sets the working directory of the docker container
-p PORT_ON_HOST:PORT_ON_CONTAINER
Maps the port on the host machine to the port on a container. Example: If you had a container running a web server on PORT_ON_CONTAINER, you can do an http request on that container using PORT_ON_HOST.
--rm
When the container stops, remove itself
--name CONTAINER_NAME
Specify the name of the container
By default, docker containers are isolated. The containers do not know about each other or how to talk to one other. They do not share a file system.
docker run -v DIRECTORY_FROM_HOST:DIRECTORY_YOU_WANT_TO_MOUNT_TO
Example: docker run -v ${PWD}:/my_cool_directory_that_will_be_created_on_my_container
Docker Volumes. Creates a mount point between the host (where the container is running from) and the container itself. Allows host and containers to share files between each other.
Examples:
- The following works on both PowerShell and Unix:
docker run --rm -it -v ${PWD}:/usr/src/project gcc:4.9 - For additional information: https://stackoverflow.com/questions/41485217/mount-current-directory-as-a-volume-in-docker-on-windows-10
docker stop $(docker ps -a -q)
Stops all containers
docker logs INSERT_CONTAINER_NAME_OR_ID
Prints logs of a docker container
docker logs INSERT_CONTAINER_NAME_OR_ID -f
Follows the logs of a container
docker inspect INSERT_CONTAINER_NAME_OR_ID
See numerous settings about a docker container
Dockerfile syntax
- FROM
- EXPOSE
- RUN
- COPY
- WORKDIR
- CMD
--
- FROM INSERT_BUILD_HERE
- EXPOSE INSERT_PORT_HERE
- RUN INSERT_COMMAND_HERE
- COPY FILE_FROM_HOST DIRECTORY_ON_CONTAINER
- WORKDIR SET_WORKING_DIRECTORY_HERE
- CMD EXECUTE_THIS_COMMAND_ON_CONTAINER_STARTUP
--
- A DockerFile always starts with a FROM command
- Difference between RUN and CMD listed here. Quick Summary: RUN triggers while docker image is built. CMD trigger when a docker image is launched.
--
Dockerfile reference: https://docs.docker.com/engine/reference/builder/
docker build -t INSERT_NAME_OR_TAG_HERE INSERT_LOCATION_OF_DOCKERFILE
or (example below)
docker build -t nodejs-app .
Uses the DockerFile to build an image. It is important to mention that The -t flag both tags and name the container. https://docs.docker.com/engine/reference/commandline/build/
docker images
Lists the docker images on the host machine
docker rmi INSERT_NAME_OF_IMAGE
Deletes a Docker image
docker-compose -f INSERT_FILE_NAME_HERE up CHOOSE_SERVICE_FROM_THAT_FILE_HERE
Runs a service from a docker-compose file.
docker-compose rm -f
When process is closed, forcefully cleanup docker-compose
docker rm -f INSERT_CONTAINER_NAME_OR_ID
Forcefully remove a Docker container
docker network prune
Removes all Docker networks
When you stop a docker container with a database, the data will remain. HOWEVER, if you remove a docker container, that data will vanish. Volume mounting can be used to persist the data.
docker-compose represents environments. (Example: An application that depends on RabitMQ, MongoDB, Redis, etc.) The compose file can make it so that you have a source of truth for environment setup.
In most use cases, you most likely you will not need to use Scratch. Meant for high performance, applications that would compile down to a native process.
More on Docker Compose:
- Supercharged Docker with Docker Compose by Engineer Man: https://www.youtube.com/watch?v=2qKlZQX1Ums. Examples located at: https://github.com/engineer-man/youtube/tree/master/066
Networking with Docker:
- https://hackernoon.com/build-a-crud-api-with-mongodb-express-and-docker-70510c6f706b
- (Official Reference) https://docs.docker.com/network/
For additional content, like Security or running a Java application in Docker, check out the following link: