It’s relatively easy to set up a Docker registry and start populating it with Docker images. Most registries require just a few steps to get started.
It’s often harder, however, to ensure that your Docker registry is optimally configured for privacy, security and other needs. The default configurations of most registries tend not to be ideal for organizations that require features such as strong control over access to their images, integrated image scanning or image version management. This means that it’s important to take extra steps after launching a Docker registry to optimize its setup.
Read on for tips and best practices for configuring a Docker registry.
What is a Docker registry?
Before jumping into best practices for managing a Docker registry, let’s discuss what a registry is.
A Docker registry is a system that hosts container images. Developers can upload container images for their applications into the registry, and users can download them from it when they want to run the containers.
The term “Docker registry” is often used interchangeably with “container registry” because most modern registries can host container images created using both the OCI container image format and Docker’s image format. However, technically speaking, “Docker registry” refers to registries that support Docker’s image format in particular.
Optimizing your Docker registry
There are more than a dozen container registries available today. No matter which one you choose, however, chances are that its out-of-the-box configurations are not the best for your needs. Most registries prioritize simplicity by default, which means that advanced features are usually not turned on or fully configured when you first set the registry up.
To get the most out of your Docker registry, then, consider adhering to the following best practices:
Enable access controls
By default, your container registry may make images available to anyone on the Internet. That’s fine if you want to distribute all of your software to the public at large.
But if you intend to use some or all containers just inside your organization, you’ll want to enable access controls, which restrict access to images. In most registries, you can set granular access policies that define on an image-by-image basis which groups or users can access which images.
Whatever you do, don’t make the mistake of companies that accidentally leave their Docker registries open to the public, exposing sensitive information.
Enable and monitor audit logs
If you share a registry across your team or organization, you can easily lose track of which images different people have uploaded to it. That creates the risk that insecure images could make their way in. Someone could also upload images that contain sensitive data, then fail to set proper access controls to protect the data.
To guard against these risks, enable and monitor audit logs, which keep records of who has done what inside your registry. It’s also a best practice to generate lists of all images in your registry periodically, then ensure that you know what the purpose of each image is and that it’s properly secured. In general, if there’s no reason for an image to be in your registry, you should remove it.
Integrate security scanning
Many Docker registries offer integrated Docker image scanning. When enabled, these scanners can automatically scan every image in your registry for security vulnerabilities, such as the presence of malware. For example, Artifactory can integrate with Xray for deep-scanning all layers of container images stored in Artifactory.
Because scanners may be turned off by default, be sure to enable them. Be sure, too, that scans are set to run automatically whenever a new image appears or an existing image is updated. You don’t want to have to trigger image scans manually.
Manage image versions
A Docker registry could contain multiple versions of the same container image. You may have a stable version, which will be used by most users. You may also have legacy versions that certain users need due to compatibility issues with the up-to-date version. And you may store bleeding-edge versions for testing purposes, too.
By default, most registries will let users download whichever image they want. That’s not always desirable because users will typically default to the latest version — which, again, could be a testing release that you don’t actually want all of your users to download yet. Or it could be a release that won’t work for users running legacy environments.
For this reason, be sure to manage the versions of each image that you house in your registry. It may be helpful to create different registries for different stages of the pipeline. For example, consider creating different development, staging and production registries. That way, you can move or copy an image to the appropriate registry based on whether the image version has met or passed certain quality gates.
Get the most out of your Docker registry
Docker registries can be powerful tools — but they often fall short of delivering their full potential if you stick with the default, out-of-the-box configuration. Unless you just need a simple registry for distributing a few container images to the public at large, take the time to configure access controls, enable advanced security features, manage image versions and audit your image lists to ensure that you’re getting the most out of your Docker registry.