kubernetes/docs/user-guide/identifiers.md

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<h2>PLEASE NOTE: This document applies to the HEAD of the source tree</h2>

If you are using a released version of Kubernetes, you should
refer to the docs that go with that version.

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<strong>
The latest release of this document can be found
[here](http://releases.k8s.io/release-1.1/docs/user-guide/identifiers.md).

Documentation for other releases can be found at
[releases.k8s.io](http://releases.k8s.io).
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# Identifiers

All objects in the Kubernetes REST API are unambiguously identified by a Name and a UID.

For non-unique user-provided attributes, Kubernetes provides [labels](labels.md) and [annotations](annotations.md).

## Names

Names are generally client-provided.  Only one object of a given kind can have a given name at a time (i.e., they are spatially unique).  But if you delete an object, you can make a new object with the same name.  Names are the used to refer to an object in a resource URL, such as `/api/v1/pods/some-name`.   By convention, the names of Kubernetes resources should be up to maximum length of 253 characters and consist of lower case alphanumeric characters, `-`, and `.`, but certain resources have more specific restrictions.  See the [identifiers design doc](../design/identifiers.md) for the precise syntax rules for names.

## UIDs

UID are generated by Kubernetes.  Every object created over the whole lifetime of a Kubernetes cluster has a distinct UID (i.e., they are spatially and temporally unique).


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