System administration
To effectively administer Compute, you must understand how the different
installed nodes interact with each other. Compute can be installed in
many different ways using multiple servers, but generally multiple
compute nodes control the virtual servers and a cloud controller node
contains the remaining Compute services.
The Compute cloud works using a series of daemon processes named nova-*
that exist persistently on the host machine. These binaries can all run
on the same machine or be spread out on multiple boxes in a large
deployment. The responsibilities of services and drivers are:
Services
- nova-api
- receives XML requests and sends them to the rest of the
system. A WSGI app routes and authenticates requests. Supports the
EC2 and OpenStack APIs. A nova.conf configuration file is created
when Compute is installed.
- nova-cert
- manages certificates.
- nova-compute
- manages virtual machines. Loads a Service object, and
exposes the public methods on ComputeManager through a Remote
Procedure Call (RPC).
- nova-conductor
- provides database-access support for Compute nodes
(thereby reducing security risks).
- nova-consoleauth
- manages console authentication.
- nova-objectstore
- a simple file-based storage system for images that
replicates most of the S3 API. It can be replaced with OpenStack
Image service and either a simple image manager or OpenStack Object
Storage as the virtual machine image storage facility. It must exist
on the same node as nova-compute.
- nova-network
- manages floating and fixed IPs, DHCP, bridging and
VLANs. Loads a Service object which exposes the public methods on one
of the subclasses of NetworkManager. Different networking strategies
are available by changing the network_manager configuration
option to FlatManager, FlatDHCPManager, or VLANManager
(defaults to VLANManager if nothing is specified).
- nova-scheduler
- dispatches requests for new virtual machines to the
correct node.
- nova-novncproxy
- provides a VNC proxy for browsers, allowing VNC
consoles to access virtual machines.
Note
Some services have drivers that change how the service implements
its core functionality. For example, the nova-compute service
supports drivers that let you choose which hypervisor type it can
use. nova-network and nova-scheduler also have drivers.