Concepts

This topic describes the key concepts of Cloudfleet Container Registry (CFCR).

Images

An image is a read-only template with instructions to create a container. An image includes the application code, runtime, libraries, and dependencies that your application needs to run. CFCR stores images that comply with Open Container Initiative specifications, including Docker images in the Docker Image Manifest V2 Schema 2 format.

You identify an image by its repository name and a version identifier (tag) or digest. For example, myapp:v1.2.3 refers to the image in the myapp repository with the tag v1.2.3.

Repositories

A repository is a collection of related images, typically different versions of the same application. Use repositories to organize and manage images in your registry.

Repository names can include forward slashes to create logical groupings. For example, backend/api and backend/worker are two separate repositories that share a common prefix. The forward slashes do not create a hierarchical directory structure. They are part of the repository name.

Examples of repository names:

• myapp
• frontend/web
• services/auth/api
• team-platform/infrastructure/base-images

Tags

A tag is a human-readable identifier for a specific version of an image within a repository. Tags are mutable: you can update a tag to point to a different image. Common tagging conventions include:

• Semantic versions: v1.0.0, v1.2.3, v2.0.0-beta
• Latest: latest typically points to the most recent stable version
• Environment: production, staging, development
• Git references: main, sha-a1b2c3d

Because tags are mutable, the image that myapp:latest refers to can change over time. For production deployments where consistency is critical, consider image digests instead of tags.

Digests

A digest is an immutable, content-addressable identifier for an image. The digest is a SHA256 hash of the image manifest. A specific digest always refers to exactly the same image content.

Digests use the format sha256: followed by a 64-character hexadecimal string:

sha256:a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4

You can reference an image by digest instead of tag:

12345678-6651-4e5d-9c04-079f6532989b.europe.registry.cloudfleet.dev/myapp@sha256:a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4

With digests, your deployments always use the exact same image, even if someone updates the tag to point to a different image.

Manifest lists

A manifest list (also known as a multi-architecture image or fat manifest) is a higher-level manifest that references multiple platform-specific images under a single tag. When you pull an image from a manifest list, the container runtime automatically selects the appropriate image for your platform.

For example, a manifest list for myapp:v1.0.0 might include:

• An AMD64 Linux image
• An ARM64 Linux image
• An AMD64 Windows image

As a result, you can use the same image reference across different architectures without specifying the platform.

Image paths

The full path to an image in CFCR follows this structure:

{organization-id}.{region}.registry.cloudfleet.dev/{repository}:{tag}

Complete example:

12345678-6651-4e5d-9c04-079f6532989b.europe.registry.cloudfleet.dev/backend/api:v1.2.3

You can also reference images by digest:

12345678-6651-4e5d-9c04-079f6532989b.europe.registry.cloudfleet.dev/backend/api@sha256:a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4

OCI artifacts

CFCR can store OCI artifacts in addition to container images. OCI artifacts are any content that conforms to the OCI distribution specification. Common examples include:

• Helm charts: Kubernetes application packages
• Software Bill of Materials (SBOM): Inventory of software components
• Signatures: Cryptographic signatures for image verification
• Configuration files: Application configuration bundles

Helm 3.8 and later can push and pull charts directly from CFCR using oci:// URLs.