MAAS supports Ubuntu and CentOS images out of the box. Ubuntu Advantage is needed in order to use Windows, RHEL and SUSE images or in order to build a custom image for any operating system.
Images are stored in the region controller's database, from where the rack controller will automatically pull them onto its local disk.
See CLI Image Management for information on advanced image management.
The place from where a region controller downloads its images is known as a boot image source. The main characteristics of a boot source are its location (URL) and its associated GPG public keyring.
MAAS comes configured with a boot source that should suffice for most users. It is located at https://images.maas.io/ephemeral-v3/daily/.
The above URL points to the 'daily' stream (for the v3 format). See Local image mirror for some explanation regarding the availability of other streams.
Although the backend supports multiple boot sources, MAAS itself uses a single source. If multiple sources are detected the web UI will print a warning and will be unable to manage images.
MAAS is only useful once it has images available to provision its nodes with. Therefore, one key task once MAAS is installed is to select and import images from the boot source. Once images have been imported MAAS will update them on an hourly basis (a sync mechanism is enabled by default).
See Select and Import Images to get started with images!