Docker understanding

2024, Oct 28    

Docker Understanding & Quick Commands

Whats Docker? Docker provides the ability to package and run an application in a loosely isolated environment called a container. The isolation and security allows you to run many containers simultaneously on a given host. Docker has some terminology to get familiar with.

We have a few terms to recognize.

• Containers
• Images
• DockerHub
• Dockerfile

What are Docker containers? Containers are lightweight and contain everything needed to run the application, so you do not need to rely on what is currently installed on the host. You can easily share containers while you work, and be sure that everyone you share with gets the same container that works in the same way.

What are Docker images? Docker images are a lightweight, standalone, executable package of software that includes everything needed to run an application: code, runtime, system tools, system libraries and settings.

A container is a runtime instance of a docker image. A container will always run the same, regardless of the infrastructure. Containers isolate software from its environment and ensure that it works uniformly despite differences for instance between development and staging.

Laymans Terms? Lets say you have a wordpress application with plugins and directories full of images and config files in different locations. Using Docker allows you to consolidate all parts of your application into a consolidated environment. This allows you to easily manage the app and its dependancies and move or upgrade the app with ease to get rid of the “it worked on my machine” or “it worked fine on the previous machine” hiccups of yesteryear.

DOCKER HUB

Docker Hub is a service provided by Docker for finding and sharing container images. You can consider it the github of docker. You can find other public docker images and versions through Dockerhub like TeamPasswordManager. Learn more at hub.docker.com

DOCKERFILE

A Dockerfile a text file that contains instructions for building a Docker image. You can consider them config files that follow steps in building a docker image. Read more below on the parameters and setting up a Dockerfile with available commands.

INSTALLATION

Docker Desktop is available for Mac, Linux and Windows https://docs.docker.com/desktop

View example projects that use Docker https://github.com/docker/awesome-compose

Check out our docs for information on using Docker https://docs.docker.com

GENERAL COMMANDS

| Command | description | | ——– | ——- | | docker -d | Start the docker daemon | | docker –help | Get help with Docker. Can also use -help on all subcommands | | docker info | Display system-wide information|

IMAGES

| Command | description | | ——– | ——- | | docker build -t | Build an Image from a Dockerfile | | docker build -t . –no-cache | Build an Image from a Dockerfile without the cache | | docker images | List local images | | docker rmi | Delete an image | | docker image prune| Remove all unused images |

DOCKER HUB

| Command | description | | ——– | ——- | | docker login -u | Login to Docker | | docker push / | Publish an image to Docker Hub | | docker search | Search Hub for an image | | docker pull | Pull an image from Docker Hub |

CONTAINERS

| Command | description | | ——– | ——- | | docker build -t . –no-cache docker run --name | Create and run a container from an image, with a custom name| | docker run -p : | Run a container with and publish a container’s port(s) to the host| | docker run -d | Run a container in the background| | docker start|stop (or )| Start or stop an existing container| | docker rm | Remove a stopped container | | docker exec -it sh | Open a shell inside a running container | | docker logs -f | Fetch and follow the logs of a container | | docker inspect (or ) | To inspect a running container | | docker ps | To list currently running containers | | docker ps --all | List all docker containers (running and stopped) | | docker container stats | View resource usage stats |