A rack controller can be connected to multiple VLANs, each from a different network interface. This provides a scaling factor that can help as a network architecture grows in size.
In regards to region controller and rack controller communication, each rack controller must be able to initiate TCP connections:
- for HTTP, to each region controller on port 5240. If high availability is implemented then this will typically become port 80.
- for RPC, to each region controller between port 5250 and 5259 inclusive. This
permits up to 10
maas-regiondprocesses on each region controller host. At present this is not configurable.
When a rack controller is installed on the same host as the region API server it will register itself automatically. Otherwise this will need to be done manually:
To install and register a rack controller you can either use the Ubuntu Server ISO or the MAAS CLI. Both will require the URL of the region API server. For nodes on an IPv6 subnet, the URL must use a hostname instead of an IP address and it must resolve to both IPv4 and IPv6 addresses, both on the rack controller and on the nodes.
Once registered, if this is an extra rack controller, it will appear immediately in the web UI and begin to sync with the primary controller:
Multiple rack controllers are needed in order to achieve specific types of high availability.
Note: If you will be using KVM-backed nodes you must ensure that the new rack controller can communicate with the KVM host. See KVM guest nodes.
If you ever want to unregister a rack controller, which is probably something you would only do to an extra one you may have added, you will need to delete it from the region API server; there is no 'unregister' command.
To do so, navigate to the 'Nodes' page and then the 'Controller' tab. Enter the controller's page by clicking on the machine you want to delete and select 'Delete' from the dropdown (and then 'Go'). MAAS will do the right thing if the controller was used for DHCP HA (i.e. DHCP HA will no longer be enabled since there is no longer the possibility of having it).
Although similar, this is not conceptually equivalent to deleting a MAAS node. Here, you are deleting a machine that is a part of MAAS itself.
Note: Unless the software on this machine is removed, rebooting it will cause the machine to re-instate itself as a rack controller. This behaviour may change with future versions of MAAS.