GitLab Container Virtual Registry with Docker Hardened Images

This post details the setup and benefits of GitLab's Container Virtual Registry, specifically highlighting its use with Docker Hardened Images. It explains how the virtual registry acts as a pull-through cache for multiple upstream registries (Docker Hub, dhi.io, MCR, Quay.io), consolidating authentication and reducing CI/CD build times by caching images. The post provides code examples for creating virtual registries and upstreams using the `virtual_registry_client` and demonstrates updating CI/CD configurations to use the virtual registry. It also discusses image path formats for different registries, cache validity, upstream priority, and limits. The UI configuration for virtual registries and upstreams is also mentioned, along with future development plans for allow/deny lists.