Docker Images and Containers

When we work with Docker, it is important to have basic knowledge of docker images and containers. Docker containers are created using docker images. We are going to look into basic commands to create docker containers using images.

Docker Image

An image is a read-only template with instructions for creating a Docker container. It is a combination of file system and parameters. Often, an image is based on another image with some additional customization.

We can use existing images or create our own images.

Docker Container

A container is a runnable instance of an image. We can create as many as we want from an image. A container is isolated from the host by default. We can modify its behavior using network, volume, etc.

When a container is created, we can stop, restart, remove it.

How to Download an Image

We can download a Docker image using 2 methods.

pull — we can use pull command to get an image

$ docker container run nginx

create a container — when we create a container from an image, it downloads the image from the repository if it is not available in the host.

Docker Command Structure

There are many commands in docker. So Docker has grouped them together into a common format.

docker COMMAND SUBCOMMAND
$ docker container ls

Useful Docker Commands

docker image ls — list available images
docker image rm — remove an image
docker image inspect — inspect an image
docker container run — run a container
docker container ls — list containers
docker container stop — stop a running container

Dry Run

Let's test these commands with nginx.

$ docker container run --name my-nginx -p 80:80 nginx
$ docker image ls
$ docker container ls

Visit localhost in your browser. You should see nginx is running.

We can inspect image and container using inspect command.

$ docker container inspect my-nginx
$ docker image inspect nginx

How to Stop a Container

 $ docker container stop my-nginx

Verify whether it is running by using ls command.

$ docker container ls
$ docker container ls -a

Starting a Stopped Container

 $ docker container start my-nginx

Removing the Container

First stop the running container. Then use remove command to remove it.

$ docker container stop my-nginx
$ docker container remove my-nginx

Removing the Image

 $ docker image remove nginx

That's all for now. Thanks for reading

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