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Image Tags

Docker image tags are labels used to identify, version, and manage different iterations of a container image. Think of them as "sticky notes" that provide context about what is inside a specific image.

Docker Tags

Core Concepts​

  • Syntax: Tags are appended to an image name using a colon: image_name:tag (e.g., my-app:1.0.0).
  • Default Tag: If you do not specify a tag, Docker automatically assigns the latest tag.
  • Flexibility: A single image can have multiple tags, allowing you to point to the same build with different aliases (e.g., my-app:1.2.3 and my-app:latest).

Best Practices​

  • Avoid :latest in Production: The latest tag is a "floating" tag, meaning it is constantly overwritten. In production environments, it can lead to unpredictable deployments. Always use specific, immutable versions for production.
  • Use Semantic Versioning (SemVer): Tagging images with version numbers (e.g., 1.2.3) is the industry standard. It provides a clear history of updates and makes rollbacks significantly easier.
  • Incorporate Traceability: For development and CI/CD pipelines, consider tags that map directly to your source code, such as Git SHAs or Build IDs.