7 Docker Tagging Best Practices

Tagging is an important part of working with Docker images. It allows you to specify a particular version or variants of an image, which can be useful when you need to roll back to a previous version or deploy a specific version to production.

In this article, we will discuss 7 best practices for tagging Docker images. By following these best practices, you can ensure that your images are properly tagged and easy to manage.

1. Use a consistent tagging scheme

When you use a consistent tagging scheme, it’s much easier to manage and organize your images. For example, let’s say you have two different versions of the same image, one for development and one for production.

If you use a consistent tagging scheme, you can tag them as such:

my-image:dev
my-image:prod

This makes it clear at a glance which image is which, and you can easily pull the correct image for the environment you’re working in.

Additionally, using a consistent tagging scheme makes it easy to automate image management tasks, such as building and pushing images to a registry.

2. Tag the same image with multiple tags

When you push an image to a registry, you’re not just pushing the code contained within that image. You’re also pushing all of the metadata associated with that image, including any tags.

This is important for two reasons. First, it means that if you tag an image with multiple tags, you only need to push it once. Second, it means that you can use different tags to represent different versions of the same image.

For example, you could have a “latest” tag that always points to the most recent version of your image, and a “stable” tag that points to the most stable version of your image. This is a great way to make sure that your users are always using the most up-to-date version of your software, while still having access to older versions if they need them.

3. Don’t use latest as your default tag

When you use “latest” as your default tag, you’re implicitly saying that the code in that image is good enough to go into production. But if that’s not actually the case, you could end up deploying code that’s not ready for prime time, which can cause all sorts of problems.

It’s much better to use a specific version number (or commit hash) as your default tag, so that you can always deploy the exact same code that you’ve tested and know to be working.

4. Be careful when pushing to Docker Hub

If you push an image with a tag that already exists on Docker Hub, the previous image will be overwritten. This can cause problems if someone has already pulled the image and is using it in production.

To avoid this, always use a new tag when pushing to Docker Hub. If you need to update an image, you can push it with a new tag and then update the tag on Docker Hub.

It’s also a good idea to keep your tags consistent across all of your images. For example, if you’re using Semantic Versioning, you should use the same tagging scheme for all of your images. This will make it easier for people to understand and use your images.

5. Know what you are pulling from Docker Hub

When you run the command “docker pull” without specifying a tag, Docker defaults to pulling the “latest” tag. However, what exactly is the “latest” tag? The answer may surprise you.

The “latest” tag is not necessarily the most recent version of the image. In fact, it’s often quite old. For example, at the time of this writing, the latest tag for the nginx image is 1.13.3, which was released over six months ago.

This can cause problems if you are relying on the “latest” tag to always be up-to-date. To avoid these problems, it’s best to specify the exact tag that you want to pull when running the “docker pull” command.

6. Consider using digests for production deployments

When you use a tag like “latest” or “stable”, you’re implicitly trusting that the person who built the image didn’t do anything malicious. For example, they could have added a secret key into the image that gives them access to your production environment.

On the other hand, when you use a digest, you’re trusting that the content of the image hasn’t been tampered with, because the digest is a cryptographic hash of the contents of the image. So if someone tries to change the contents of the image, the digest will no longer match, and Docker will refuse to run it.

This is why digests are considered more secure than tags, and you should consider using them for production deployments.

7. Keep an eye on security updates

If you’re not familiar with docker, it’s a tool that allows developers to package up an application with all of its dependencies into a “container.” This makes it easy to deploy and run the application on any server.

Docker containers are often used to run web applications. And because they can be deployed anywhere, they can be a target for attackers. That’s why it’s important to keep your containers up to date with the latest security patches.

The best way to do this is to use a tool like Quay.io, which will automatically update your containers when new security patches are released.

By keeping your containers up to date, you can help protect your applications from attack.