The docker build command creates a new image that is only available on the local machine. This can be a hassle when you're working with other developers and need to share your images with them.
That's where Docker Hub comes in. It is a platform that allows you to host your Docker images and make them easily accessible to other people. It eliminates the need for others to run docker build every time they want to use your image, and it's much simpler than sharing a link to your code base with a README file detailing the setup process.
Docker Hub
Docker Hub is a widely used public registry for storing and managing Docker images. It offers features such as image storage, versioning, and collaboration tools for working with images.
In this topic, you will focus on using Docker Hub as the primary registry for storing and sharing images. However, it is worth noting that there are other popular options available, such as the Google Container Registry and the Amazon Elastic Container Registry. These registries provide similar functionality as Docker Hub, but they are operated by different companies and may have slightly different features or pricing plans.
To use Docker Hub, users are required to create an account. Accounts can be either free or paid. Free accounts have limitations such as storage and the number of private repositories.
Additionally, private registries are often used within an organization and can be run on a server or personal computer. While these are typically used as more secure alternatives to public registries, they are outside the scope of this topic.
Let's look at how you can create and log in to a Docker Hub account.
Logging in to Docker Hub
To log in to Docker Hub, you first need to create an account on the Docker Hub website. Once you have an account, you can use the docker login command in your command line interface to authenticate.
The basic syntax of the command is docker login [options] [server], where options can be used to specify the credentials and server is the URL of the registry you want to log in to. For example, docker login --username myusername --password mypassword https://index.docker.io/v1/.
You will be prompted to enter your credentials if you do not include the username and password in the command.
In this topic, you will work with the hello-world sample image. This image can be pulled from Docker Hub using the following command:
docker pull hello-worldNow, let's talk about image tagging.
Tagging the image
Tags are labels or names that can be applied to an image to indicate a version or a specific release. Latest is the default for Docker Hub, but it is best practice to specify a tag that is relevant to your project to ensure clear versioning and organization. Developers usually choose tags that are descriptive and meaningful, such as a version number or a specific release date. SemVer is a common versioning scheme used by many open-source projects.
Adding your own tag to the image
You can tag the image with your Docker Hub username using the following command:
docker tag hello-world:[tag] [docker_hub_username]/hello-world:[tag]For example, if your Docker Hub username is johndoe and you have an image named hello-world with the tag v1.0, the tag command will be:
docker tag hello-world:latest johndoe/hello-world:v1.0After tagging the image, it can be pushed to the registry.
Pushing the image
You can push images to the registry using the docker push command. When you execute the command, the image is sent to the Docker Hub registry and is stored in the specified repository, under the username and the specified tag.
To push a tagged Docker image to a registry, use the following command:
docker push [docker_hub_username]/hello-world:[tag]Replace [docker_hub_username] with your Docker Hub username and [tag] with the desired tag name.
For example, to push a hello-world image with tag v1.0 to Docker Hub under the username johndoe, the command will be:
docker push johndoe/hello-world:v1.0 Pulling the image
Once an image is pushed to a registry, it can be easily retrieved and used by other developers using the docker pull command.
To test our new hello world code, run the following command:
docker pull docker.io/johndoe/hello-world:v1.0Conclusion
In conclusion, Docker Hub is a convenient platform for storing and sharing Docker images. By following the steps outlined in this text, users can easily log in, tag images, push images to the registry, and pull images from Docker Hub.
When the command is executed, the image is sent to the Docker Hub registry and is stored in the specified repository, under the username and tag specified.
More information on the proper use of registries can be found in the official documentation at docs.docker.