# 5. Orchestration: Building Systems with Docker

## Registries in detail

Companies will create their own docker registry

### What is a Docker Registry?

* It's a program
* Stores layers and images
* Listens on (by default) port 5000
* Maintains an index and search tags
* Authorizes and authenticates connections (sometimes)

### Popular Docker Registry Programs

* Official Docker registry
* Nexus

### Running the Docker Registry in Docker
* Docker makes installing network service easy
* The registry is a Docker service