Apply custom metadata (Engine)

Apply custom metadata

You can apply metadata to your images, containers, or daemons via labels. Labels serve a wide range of uses, such as adding notes or licensing information to an image, or to identify a host.

A label is a <key> / <value> pair. Docker stores the label values as strings. You can specify multiple labels but each <key> must be unique or the value will be overwritten. If you specify the same key several times but with different values, newer labels overwrite previous labels. Docker uses the last key=value you supply.

Note: Support for daemon-labels was added in Docker 1.4.1. Labels on containers and images were added in Docker 1.6.0

Label keys (namespaces)

Docker puts no hard restrictions on the key used for a label. However, usi