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# FSEntityIdentifier

A base type that identifies containers and volumes.

```
class FSEntityIdentifier
```

## Overview

An [`FSEntityIdentifier`](/documentation/FSKit/FSEntityIdentifier) is a UUID to identify a container or volume, optionally with eight bytes of qualifying (differentiating) data.
You use the qualifiers in cases in which a file server can receive multiple connections from the same client, which differ by user credentials.
In this case, the identifier for each client is the server’s base UUID, and a unique qualifier that differs by client.

> Important: Don’t subclass this class.

## Topics

### Creating an entity identifier

[`init()`](/documentation/FSKit/FSEntityIdentifier/init())

Creates an entity identifier with a random UUID.

[`init(uuid:)`](/documentation/FSKit/FSEntityIdentifier/init(uuid:)-9e20k)

Creates an entity identifier with the given UUID.

[`init(uuid:data:)`](/documentation/FSKit/FSEntityIdentifier/init(uuid:data:)-8dixs)

Creates an entity identifier with the given UUID and qualifier data.

[`init(uuid:qualifier:)`](/documentation/FSKit/FSEntityIdentifier/init(uuid:qualifier:)-9ty70)

Creates an entity identifier with the given UUID and qualifier data as a 64-bit unsigned integer.

### Inspecting identifier properties

[`uuid`](/documentation/FSKit/FSEntityIdentifier/uuid)

A UUID to uniquely identify this entity.

[`qualifier`](/documentation/FSKit/FSEntityIdentifier/qualifier)

An optional piece of data to distinguish entities that otherwise share the same UUID.


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