![]() ![]() Manifest digest - Each container image pushed to a container registry is associated with a manifest, identified by a unique SHA-256 hash, or digest. In general, a Git commit provides a semi-stable tag. If a base image update happens, your build system kicks off with the same Git commit as the previous build. Git commit – This approach works until you start supporting base image updates. But, how to correlate it back to your build system? Do you have to find the build that was completed at the same time? What time zone are you in? Are all your build systems calibrated to UTC? There are several patterns you can follow to generate unique tags, including:ĭate-time stamp - This approach is fairly common, since you can clearly tell when the image was built. Unique tagging simply means that every image pushed to a registry has a unique tag. If your container restarts or an orchestrator scales out more instances, your hosts won’t accidentally pull a newer version, inconsistent with the other nodes. You likely want deliberate deployments of a consistent version of components. Recommendation: Use unique tags for deployments, especially in an environment that could scale on multiple nodes. For example, auto-purge untagged manifests older than a specified duration, or set a retention policy for untagged manifests. ![]() To maintain your registry size, you can periodically delete untagged manifests resulting from stable image updates. The previous image's manifest and unique layer data remain in the registry. If an image with a stable tag is updated, the previously tagged image is untagged, resulting in an orphaned image. From a base image scenario, this allows the image owner to provide serviced images. In this case, both the major and minor tags are continually being serviced. When base image updates are available, or any type of servicing release of the framework, images with the stable tags are updated to the newest digest that represents the most current stable release of that version. :1.0- a stable tag for version 1.0, allowing a developer to bind to updates of 1.0, and not be rolled forward to 1.1 when it is released.1 represents the “newest” or “latest” 1.* version. :1 – a stable tag for the major version.To support stable tags for a given major and minor version, they have two sets of stable tags. ![]() They know they’ll ship updates, including minor updates. ExampleĪ framework team ships version 1.0. To stay “stable”, it might be serviced to apply security patches or framework updates. Rather, stable implies the image should be stable for the intent of that version. Stable doesn’t mean the contents are frozen. Stable tags mean a developer, or a build system, can continue to pull a specific tag, which continues to get updates. Avoid deployments with stable tags, because those tags continue to receive updates and can introduce inconsistencies in production environments. Recommendation: Use stable tags to maintain base images for your container builds.
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