..
      Copyright 2010-2012 United States Government as represented by the
      Administrator of the National Aeronautics and Space Administration.
      All Rights Reserved.

      Licensed under the Apache License, Version 2.0 (the "License"); you may
      not use this file except in compliance with the License. You may obtain
      a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
      WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
      License for the specific language governing permissions and limitations
      under the License.

========================
OpenStack Compute (nova)
========================

What is nova?
=============

Nova is the OpenStack project that provides a way to provision compute
instances (aka virtual servers). Nova supports creating virtual machines,
baremetal servers (through the use of ironic), and has limited support for
system containers. Nova runs as a set of daemons on top of existing Linux
servers to provide that service.

It requires the following additional OpenStack services for basic function:

* :keystone-doc:`Keystone <>`: This provides identity and authentication for
  all OpenStack services.
* :glance-doc:`Glance <>`: This provides the compute image repository. All
  compute instances launch from glance images.
* :neutron-doc:`Neutron <>`: This is responsible for provisioning the virtual
  or physical networks that compute instances connect to on boot.
* :placement-doc:`Placement <>`: This is responsible for tracking inventory of
  resources available in a cloud and assisting in choosing which provider of
  those resources will be used when creating a virtual machine.

It can also integrate with other services to include: persistent block
storage, encrypted disks, and baremetal compute instances.

For End Users
=============

As an end user of nova, you'll use nova to create and manage servers with
either tools or the API directly.

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   user/index

Tools for using Nova
--------------------

* :horizon-doc:`Horizon <user/launch-instances.html>`: The official web UI for
  the OpenStack Project.
* :python-openstackclient-doc:`OpenStack Client <>`: The official CLI for
  OpenStack Projects. You should use this as your CLI for most things, it
  includes not just nova commands but also commands for most of the projects in
  OpenStack.
* :python-novaclient-doc:`Nova Client <user/shell.html>`: For some very
  advanced features (or administrative commands) of nova you may need to use
  nova client. It is still supported, but the ``openstack`` cli is recommended.

Writing to the API
------------------

All end user (and some administrative) features of nova are exposed via a REST
API, which can be used to build more complicated logic or automation with
nova. This can be consumed directly, or via various SDKs. The following
resources will help you get started with consuming the API directly.

* `Compute API Guide <https://docs.openstack.org/api-guide/compute/>`_: The
  concept guide for the API. This helps lay out the concepts behind the API to
  make consuming the API reference easier.
* `Compute API Reference <https://docs.openstack.org/api-ref/compute/>`_:
  The complete reference for the compute API, including all methods and
  request / response parameters and their meaning.
* :doc:`Compute API Microversion History </reference/api-microversion-history>`:
  The compute API evolves over time through `Microversions
  <https://docs.openstack.org/api-guide/compute/microversions.html>`_. This
  provides the history of all those changes. Consider it a "what's new" in the
  compute API.
* :doc:`Block Device Mapping </user/block-device-mapping>`: One of the trickier
  parts to understand is the Block Device Mapping parameters used to connect
  specific block devices to computes. This deserves its own deep dive.
* :doc:`Metadata </user/metadata>`: Provide information to the guest instance
  when it is created.

Nova can be configured to emit notifications over RPC.

* :doc:`Versioned Notifications </admin/notifications>`: This
  provides information on the notifications emitted by nova.

Other end-user guides can be found under :doc:`/user/index`.

For Operators
=============

Architecture Overview
---------------------

* :doc:`Nova architecture </admin/architecture>`: An overview of how all the parts in
  nova fit together.

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   admin/architecture

Installation
------------

.. TODO(sdague): links to all the rest of the install guide pieces.

The detailed install guide for nova. A functioning nova will also require
having installed :keystone-doc:`keystone <install/>`, :glance-doc:`glance
<install/>`, :neutron-doc:`neutron <install/>`, and
:placement-doc:`placement <install/>`. Ensure that you follow their install
guides first.

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   install/index

Deployment Considerations
-------------------------

There is information you might want to consider before doing your deployment,
especially if it is going to be a larger deployment. For smaller deployments
the defaults from the :doc:`install guide </install/index>` will be sufficient.

* **Compute Driver Features Supported**: While the majority of nova deployments use
  libvirt/kvm, you can use nova with other compute drivers. Nova attempts to
  provide a unified feature set across these, however, not all features are
  implemented on all backends, and not all features are equally well tested.

  * :doc:`Feature Support by Use Case </user/feature-classification>`: A view of
    what features each driver supports based on what's important to some large
    use cases (General Purpose Cloud, NFV Cloud, HPC Cloud).
  * :doc:`Feature Support full list </user/support-matrix>`: A detailed dive through
    features in each compute driver backend.

* :doc:`Cells v2 configuration </admin/cells>`: For large deployments, cells v2
  cells allow sharding of your compute environment. Upfront planning is key to
  a successful cells v2 layout.

* :doc:`Running nova-api on wsgi <user/wsgi>`: Considerations for using a real
  WSGI container instead of the baked-in eventlet web server.

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   user/feature-classification
   user/support-matrix
   admin/cells
   user/wsgi

Maintenance
-----------

Once you are running nova, the following information is extremely useful.

* :doc:`Admin Guide </admin/index>`: A collection of guides for administrating
  nova.
* :doc:`Flavors </user/flavors>`: What flavors are and why they are used.
* :doc:`Upgrades </admin/upgrades>`: How nova is designed to be upgraded for minimal
  service impact, and the order you should do them in.
* :doc:`Quotas </user/quotas>`: Managing project quotas in nova.
* :doc:`Aggregates </admin/aggregates>`: Aggregates are a useful way of grouping
  hosts together for scheduling purposes.
* :doc:`Scheduling </admin/scheduling>`: How the scheduler is
  configured, and how that will impact where compute instances land in your
  environment. If you are seeing unexpected distribution of compute instances
  in your hosts, you'll want to dive into this configuration.
* :doc:`Exposing custom metadata to compute instances </admin/vendordata>`: How
  and when you might want to extend the basic metadata exposed to compute
  instances (either via metadata server or config drive) for your specific
  purposes.

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   admin/index
   user/flavors
   admin/upgrades
   user/quotas
   admin/vendordata

Reference Material
------------------

* :doc:`Nova CLI Command References </cli/index>`: the complete command reference
  for all the daemons and admin tools that come with nova.
* :doc:`Configuration Guide <configuration/index>`: Information on configuring
  the system, including role-based access control policy rules.

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   configuration/index

For Contributors
================

* :doc:`contributor/contributing`: If you are a new contributor this should
  help you to start contributing to Nova.
* :doc:`contributor/index`: If you are new to Nova, this should help you start
  to understand what Nova actually does, and why.
* :doc:`reference/index`: There are also a number of technical references on
  both current and future looking parts of our architecture.
  These are collected here.

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   contributor/index
   contributor/contributing
   reference/index

.. only:: html

   Search
   ======

   * :ref:`Nova document search <search>`: Search the contents of this document.
   * `OpenStack wide search <https://docs.openstack.org>`_: Search the wider
     set of OpenStack documentation, including forums.
