Image registries¶
An image registry is a server-side entity that points to a global, read-only source of images, such as a SimpleStreams server or another LXD server. A registry does not store any images itself; it records the location of the image source and the protocol used to reach it, so that LXD can download images from that source.
See How to manage image registries for instructions on how to create and manage image registries, and Built-in image registries for the registries that are built in to LXD.
Registry protocols¶
An image registry uses one of the following protocols, depending on the type of image source it points to:
simplestreamsThe image source is a pure image server that uses the simple streams format. The built-in registries are all
simplestreamsregistries.You configure a
simplestreamsregistry with theurlof the image server (which must use HTTPS).lxdThe image source is another LXD server, reached through a cluster link. This can be a LXD server that is used solely to serve images, or a regular LXD server that also serves images in addition to running instances.
You configure a
lxdregistry with the name of theclusterlink that connects to the source server. Use a public cluster link for a public LXD server, or a unidirectional or bidirectional cluster link to authenticate to a private server.
For a public LXD server that is used solely to serve images, set the core.https_address configuration option and mark the images that you want to share as public (see How to expose LXD to the network for more information).
For a private LXD server, restrict access to the remote API and configure an authentication method (see Remote API authentication).
Configuration options¶
Image registries can be configured through a set of key/value configuration options. See Configure an image registry for instructions on how to set these options.
The following options are available:
| Key: | cluster |
| Type: | string |
| Required: | no |
| Key: | source_project |
| Type: | string |
| Required: | no |