Docker Images and Containers

by Azhar Uddin Technical Architect

A Docker container is just a basic version of the Linux operating system. The image below shows the software that is loaded into the container.
After you ran the previous command, Docker did the following:
1. Checked whether the “hello-world” software image had been installed or not.
2. Visited the Docker hub, found the software image, and then downloaded it onto your system.
3. The image was then loaded into the container and then run.

- It is the first time we have mentioned the Docker Hub. At this stage, just know that it is a repository where Docker images can be found. Once you develop or create your own Docker image, you can upload it to the Docker Hub. From there other people can find it to download and use. You can also download images which have been created by others from the Docker Hub and then use them on your system. A Docker hub can also be made either private or public. If you choose a private one, it will only be visible to yourself while a public one can be shared by multiple people.

- There are different variations of the Docker image. Some of the images, such as the one we have used in this book, execute just a simple and single command and then it exists. This is what happened with our previous “hello-world” command. In most cases, however, people want to use Docker to perform complex tasks.

- This means that Docker can be used to perform extra tasks. It can be used for them to start and operate complex software such as a database for the user. You can add data to the database and then store it via Docker. The data can also wait to be operated on by the next person.

- With Docker, people can create software and then share it via the Docker images. The good thing about this is that you do not have to worry about whether an image can run on the Docker image. Docker container can run any type of software. This shows the kind of flexibility and portability which it creates. The process of developing the software can also be done inside Docker and then the software can be uploaded on the Docker Hub.

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Finding and Running a Whalesay Image

People from different parts of the world can create Docker images. The images that are uploaded to the Docker Hub can then be accessed by anyone using Docker. Feel free to browse it and then find the images that you want. However, it is good for you to understand the kind of image that you need. This chapter of the book will help to guide you in this.