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< OpsGuide
Revision as of 14:16, 8 August 2013 by Hartsock (talk | contribs) (V)

#!wiki caution
'''All future updates should be put in the official glossary at http://docs.openstack.org'''


Table of Contents

0 MQ

  • An alternative name for ZeroMQ.

64 bit

  • Nova supports 64 bit VM instances so long as the underlying hypervisor and CPU supports them as well.


Table of Contents

Active Directory

  • Authentication and identity service by Microsoft, based on LDAP, currently not suppored in OpenStack.

Absolute Limit

  • Impassable limits for Nova virtual machines, settings include total RAM size, maximum number of vCPUs, and maximum disk size.

Access Key

  • Alternative term for an Amazon EC2 Access Key.


  • The Swift context of an account, not to be confused with a user account from an identity service (Active Directory, /etc/passwd, OpenLDAP, Keystone, etc).


  • Nova provides accounting information via the event notification and system usage data facilities.

Account Auditor

  • Checks for missing replicas, incorrect, and corrupted objects in a specified Swift account by executing queries against the backend sqlite database.

Account Database

  • A sqlite database that contains Swift accounts and related metadata and is accessed by the accounts server.

Account Reaper

  • A Swift worker that scans for and deletes account databases that have been marked for deletion on an account server.

Account Server

  • Provides the listing of Containers in Swift, stores it's information in the account database.

Account Service

  • Component of Swift that provides account services such as list, create, modify, and audit. Not to be confused with Keystone, OpenLDAP, or similar user account services.

Address Pool

  • A group of fixed and/or floating IP addresses that are assigned to a Nova project and can in turn be used by or assigned to the project's VM instances.

Admin API

  • A subset of API calls that are accessable to only authorized administrators and are generally not accessable to end users or the public internet, can exist as a separate service (Keystone) or can be a subset of another API (Nova).

Admin Server

  • In the context of Keystone this is the worker process that that provides access to the admin API.

Advanced RISC Machine (ARM)

  • Lower power consumption CPU often found in mobile and embedded devices, supported by OpenStack.


  • Nova can send alerts using it's notification system which includes a facility to create custom notification drivers. Alerts can be sent to and displayed on the Horizon dashboard.


  • The process of taking floating IP address from the address pool so it can be associated with a fixed IP on a Nova virtual machine instance.

Advanced Message Queuing Protocol (AMQP)

  • The open standard messaging protocol used by Nova for intra-service communications, provided by RabbitMQ (the default), Qpid or ZeroMQ.

Amazon Kernel Image (AKI)

  • Both a virtual machine container format and a virtual machine disk format, supported by Glance.

Amazon Machine Image (AMI)

  • Both a virtual machine container format and a virtual machine disk format, supported by Glance.

Amazon Ramdisk Image (ARI)

  • Both a virtual machine container format and a VM disk format, supported by Glance.


  • A project to port the shell script based project named devstack to Python.

Apache License 2.0

  • All OpenStack core projects are provided under the terms of the Apache License 2.0 license.

API Endpoint

  • The daemon, worker or service that a client communicates with in order to access an API. API endpoints can provide any number of services such as Keystone authentication, sales data, performance metrics, Nova virtual machine commands, census data, and so on.

API Extension

  • A feature of Nova and Quantum that allows custom modules to extend their core APIs.

API Extension Plug-in

  • Alternative term for a Quantum plug-in or Quantum API extension.


  • Alternative term for an API token.

API Server

  • Any node running a daemon or worker that provides an API endpoint.

API Token

  • A token that is sent along with API requests and is used by OpenStack to verify if the client is authorized to execute the requested operation.

API Version

  • In OpenStack a project's API version is part of the URL (eg: example.com/nova/v2/foobar vs example.com/nova/v1/foobar).

Application Programming Interface (API)

  • A collection of specifications used to access a service, application, or program. Includes service calls, required parameters for each call, and the expected return values.


  • Used along with iptables, ebtables, and ip6tables in Nova to provide firewall services.


  • The process associating a Nova floating IP address to a fixed IP address.

Asynchronous JavaScript and XML (AJAX)

  • Used extensively in Horizon.

ATA over Ethernet (AoE)

  • The ATA disk storage protocol tunneled within Ethernet, currently not supported in Nova.


  • The process of connecting a VIF or vNIC to a L2 network in Quantum.
  • In the context of Nova this is the process of connecting a storage volume to an instance.


  • Provided in Nova via the system usage data facility.


  • A worker processes that verifies the integrity of Swift's objects, containers, and accounts.
  • Auditors (plural) is the collective term for Swift's account auditor, container auditor, and object auditor.


  • Project name for the initial release of OpenStack.

Auth Node

  • Alternative term for a Swift authorization node.


  • The process of confirming the user, process, or client is really who they say they are via private key, secret token, password, fingerprint, or similar method.

Authentication Token

  • A string of text provided to the client after they authenticate successfully, must be provided by the user or process in subsequent requests to the API endpoint.


  • The component of Keystone that provides authentication services.


  • The act of verifying that a user, process, or client can perform the reuqested action (delete a Swift object, list a Swift container, start a Nova virtual machine, reset a user's password, etc).

Authorization Node

  • A Swift node that provides authorization services.


  • The component of Keystone that provides high-level authorization services.

Auto ACK

  • Configuration setting within Nova's RabbitMQ that enables or disables message acknowledgement, enabled by default.

Auto Declare

  • A Nova RabbitMQ setting that determines if a message exchange is automatically created when the program starts.

Availability Zone

  • An Amazon EC2 concept of an isolated area that is used for fault tolerance, not to be confused with an OpenStack Nova zone or cell.


Table of Contents


  • General term for interactions and processes that are obfuscated from the user such as Nova mounting a volume, a daemon sending data to an iSCSI target, or Swift checking the integrity of an object.

Backend Catalog

  • The storage method used by Keystone's catalog service to store and retreive information about API endpoints that are available to the client. Examples include a SQL database, LDAP database, or KVS backend.

Backend Store

  • Describes the persistent data store used to save and retreive a service's information such as a listing of Swift's objects, the current state of a Nova virtual machine, a list of user names and so on.
  • Method that Glance uses to retrieve and store virtual machine images, options include Swift, local file system, S3, or HTTP.


  • A Glance container format that indicates there is no container for the virtual machine image.


  • Project name for the second release of OpenStack.

Block Migration

  • A method of virtual machine live migration used by KVM to evacuate instance(s) from one host to another with very little downtime during a user-initiated switch-over, does not require shared storage, supported by Nova.

Bootable Disk Image

  • Type of virtual machine image that exists as a single, bootable file.

Bootstrap Protocol (BOOTP)

  • Provided in Nova via the dnsmasq daemon when using either the FlatDHCP manager or VLAN manager network manager.

Builder File

  • Contains a Swift ring's configuration informaton and is used to re-configure the ring or to re-create it from scratch after a serious failure.

Button Class

  • A group of related button types within Horizon. Buttons to start/stop/suspend virtual machines are in one class, buttons to associate and dissassociate floating IP addresses are in another, and so on.


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Cache Pruner

  • An executable program that is used to keep Glance's virtual machine image cache at or below it's configured maximum size.


  • Project name for the third release of OpenStack.


  • One of the RPC primitives used by OpenStack's message queue software, sends a message and waits for a response.


  • Defines a cell's resources (CPU, storage, networking), can apply to the cell as a whole or can only apply to specific services (CPU, storage, networking) within the cell.

Capacity Cache

  • A table within the Nova backend database that contains the current workload, amount of free RAM, number of virtual machines running on each host and is used when determining which virtual machine a host will start on.

Capacity Updater

  • A notification driver that monitors virtual machine instances and updates the capacity cache as needed.


  • One of the RPC primitives used by OpenStack's message queue software, sends a message and does not wait for a response.


  • Contains a list of available API endpoints to a user after they authenticate to Keystone.

Catalog Service

  • A Keystone service that provides a list of available API endpoints to a user after they authenticate to Keystone.


  • An incubated project that aims to provide metering and billing facilities for OpenStack.


  • Provides logical partitioning of Nova resources in a child / parent relationship, requests are passed from parent cells to child cells if the parent cannot provide the requested resource.

Cell Forwarding

  • A Nova option that allows parent cells to pass resource requests to their child cells if the parent cannot provide the requested resource.

Cell Manager

  • The component of Nova that contains a list of each host's current capabilities within the cell and routes requests as appropriate.


  • A Linux distribution that is compatible with OpenStack.


  • Massively scalable distributed storage system that consists of an object store, block store and a POSIX-compatible distributed file system, compatable with OpenStack.


  • The POSIX-compliant file system provided by Ceph.

Certificate Authority

  • Nova provides a simple certificate authority for cloudpipe VPNs and virtual machine image decryption.

Challenge-Handshake Authentication Protocol (CHAP)

  • An iSCSI authentication method supported by Nova.

Chance Scheduler

  • A scheduling method used by Nova that randomly chooses an available host from the pool.

Changes Since

  • A Nova API parameter that allows you to download changes to the requested item since you last request as opposed to downloading a new, fresh set of data and comparing it against the old data.


  • An operating system configuration management tool supported by OpenStack.

Child Cell

  • If a requested resource (CPU time, disk storage, memory) is not available in the parent cell, the request is forwarded to it's associated child cell(s). If the child cell the fufill the reuqest it will, or it will attempt to pass the reuqest to any of it's children.


  • An incubated project that aims to spin off Nova's volume service into a separate project.

Cisco Quantum Plug-in

  • A Quantum plug-in for Cisco devices and technologies including UCS and Nexus.


  • One of the default roles in Nova's RBAC system, allows for complete system access.


  • A service in Nova used to create VPNs on a per-project basis.

Cloudpipe Image

  • A pre-made virtual machine image that serves as a cloudpipe server, essentially OpenVPN running on Linux.

Cloud Controller

  • Collection of Nova components that represent the global state of the cloud, talks to services such as Keystone authentication, Swift object storage, and node/storage workers through a queue.

Cloud Controller Node

  • A node that runs network, volume, API, scheduler and image services. Each service may be broken out into separate nodes for scalability or availability.

Cloud Data Management Interface (CDMI)

  • SINA standard that defines a RESTful API for managing objects in the cloud, currently unsupported in OpenStack.

Cloud Infrastructure Management Interface (CIMI)

  • An in-progress specification for cloud management, currently unsupported in OpenStack.

Command Filter

  • Contains a list of allowed commands within Nova's rootwrap facility.

Community Project

  • A project that is not officially endorsed by the OpenStack Foundation. If the project is successful enough it may be elevated to an incubated project and then to a core project or may be simply merged with the main code trunk.


  • OpenStack supports compression at the Linux file system level but does not support compression for things such as Swift's objects or Glance's virtual machine images.

Compute API

  • The nova-api daemon that provides access to the Nova's services, can also communicate with some outside APIs such as Amazon's EC2 API.

Compute API Extension

  • Alternative term for a Nova API extension.

Compute Controller

  • The component of Nova that chooses suitable host(s) to start virtual machine instances on.

Compute Host

  • Physical host dedicated to running only compute nodes.

Compute Node

  • A node that runs Nova's nova-compute daemon, a virtual machine instance that provides a wide range of services such as a web server, performs analytics, provides a development environment or desktop, etc.

Compute Service

  • Alternative term for the component of Nova that manages virtual machines.

Compute Service API

  • Alternative term for Nova's Compute API.

Compute Worker

  • Nova component that runs on each compute node and manages the virtual machine instance lifecycle (run, reboot, terminate, attach/detatch volumes, etc), provided by the nova-compute daemon.

Concatenated Object

  • A segmented large object within Swift that is put back together again and then sent to the client.

Consistency Window

  • The amount of time it takes for a new Swift object to become accessable to all clients.

Console Log

  • Contains the output from a Linux virtual machine's console in Nova.


  • Used to organize and store objects within Swift, similar to the concept as a Linux directory but cannot be nested.
  • Alternative term for a Glance container format.

Container Auditor

  • Checks for missing replicas or incorrect objects in the specified Swift containers via queries to the sqlite backend database.

Container Database

  • A sqlite database that contains Swift containers and related metadata and is accessed by the container server

Container Format

  • The "envelope" used by Glance to store a virtual machine image and it's associated metadata (machine state, OS disk size, etc).

Container Server

  • Component of Swift that manages containers.

Container Service

  • The component of Swift that provides container services (create, delete, list, etc).

Context Processor

  • horizon fixfixfix

Controller Node

  • Alternative term for a cloud controller node.

Core API

  • Depending on context this may mean OpenStack's core API (the OpenStack API) or the main API of a specific core project (Nova, Quantum, Glance, etc).

Core Project

  • An official OpenStack project. Currently consists of Compute (Nova), Object Storage (Swift), Image Service (Glance), Identity (Keystone), Dashboard (Horizon), Networking (Quantum), and Volume (Cinder).


  • Under Nova's distributed scheduler this is calculated by looking at the capabilities of each host relative to the flavor of the virtual machine instance being requested.


  • Data that is only known to or accessable by a user that is used to verify the user is who they say they are and presented to the server during authentication. Examples include a password, secret key, digital certificate, fingerprint, and so on.


  • An open source community project by Dell that aims to provide all necessary services to quickly deploy clouds.

Current Workload

  • An element of the Nova capacity cache that is calculated based on the number of build, snapshot, migrate, and resize operations currently in progress on a given host.


  • Alternative term for a tenant.

Customization Module

  • A user-created Python module that is loaded by Horizon in order to change the look and feel of the dashboard.


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  • A process that runs in the background and waits for requests, may or may not listen on a TCP or UDP port, not to be confused with a worker.


  • The web-based management interface for OpenStack, an alternative name for Horizon.

Dashboard Class

  • horizon fixfixfix

Database ID

  • A unique identifier given to each replica of a Swift database.

Database Replicator

  • The component of Swift that copies changes in the account, container, and object databases to other nodes.

Data Encryption

  • Both Glance and Nova support encrypted virtual machine images (but not instances).
  • In-transit data encryption is supported in OpenStack using technologies such as HTTPS, SSL, TLS, SSH.
  • Swift does not support object encryption at the application level but may support storage that uses disk encryption.

Data Table

  • horizon fixfixfix


  • The process of removing the association between a floating IP address and a fixed IP address thus returning the floating IP to the address pool.


  • A Linux distribution that is compatible with OpenStack.


  • horizon fixfixfix


  • The process of finding duplicate data at the disk block, file, and/or object level in order to minimize storage use, currently unsupported within OpenStack.

Default Panel

  • The default panel that is displayed when a user accesses the Horizon dashboard.

Default Tenant

  • New users are assigned to this Keystone tenant if no tenant is specified when a user is created.

Default Token

  • A Keystone token that is not associated with a specific tenant and is exchanged for a scoped token.

Delayed Delete

  • An option within Glance so that rather than immediately delete an image, it is deleted after a pre-defined number of seconds.

Delivery Mode

  • Setting for Nova's RabbitMQ message delivery mode, can be set to eitheer transient or persistent.

Deprecated Auth

  • An option within Nova that allows administrators to create and manage users via the nova-manage command as opposed to using Keystone.


  • One of the default roles in Nova's RBAC system and is the default role assigned to a new user.


  • In the context of Swift this refers to the underlying storage device.

Device ID

  • Maps Swift's partitions to physical storage devices.

Device Weight

  • Used to distribute the partitions among Swift's devices, usually proportional to the device's storage capacity.


  • Community project that uses shell scripts to to quickly build complete OpenStack development environments.


  • Project name for the fourth release of OpenStack.

Direct Consumer

  • An element of Nova's RabbitMQ that comes to life when a RPC call is executed. It connects to a direct exchange via a unqiue exclusive queue, sends the message, and terminates.

Direct Exchange

  • A routing table that is created within Nova's RabbitMQ during RPC calls, one is created for each RPC call that is invoked.

Direct Publisher

  • Element of RabbitMQ that provides a response to an incoming MQ message.


  • The process of removing the association between a floating IP address and fixed IP and thus returning the floating IP address to the address pool.

Disk Encryption

  • The ability to encrypt data at the file system, disk partition or whole disk level, supported within Nova virtual machines.

Disk Format

  • The underlying format that a virtual machine's disk image is stored as within Glance's backend store (AMI, ISO, QCOW2, VMDK, etc).


  • Swift provides tools to test and ensure dispersion of objects and containers in order to ensure fault tolerance.


  • A web framework used extensively in Horizon.


  • Daemon that provides DNS, DHCP, BOOTP, and TFTP services, used by Nova's VLAN manager and FlatDHCP manager.

Domain Name Service (DNS)

  • Nova supports associating DNS entries with floating IP addresses, nodes or cells so host names are consistent across reboots.

Durable Exchange

  • Nova RabbitMQ message exchange that will remain active when the server restarts.

Durable Queue

  • A Nova RabbitMQ message queue that will remain active when the server restarts.

Dynamic Host Configuration Protocol (DHCP)

  • A method to automatically configure a host's networking configuration at boot time, provided by both Quantum and Nova.


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EBS Boot Volume

  • An Amazon EBS storage volume that contains a bootable virtual machine image, currently unsupported in OpenStack.


  • Used in Nova along with arptables, iptables, and ip6tables to create firewalls and to ensure isolation of network communications.


  • Amazon's commercial compute product, similar to Nova.

EC2 Access Key

  • Used along with an EC2 secret key to access Nova's EC2 API.


  • OpenStack supports accessing the Amazon EC2 API via Nova.

EC2 Compatability API

  • Component of Nova that allows OpenStack to communicate with Amazon's EC2

EC2 Secret Key

  • Used along with an EC2 access key when communicating with Nova's EC2 API, is used to digitally sign each request.

Elastic Block Storage (EBS)

  • Amazon's commercial block storage product.

Empty Role

  • Keystone role with no capabilities, allows the administrator to later add capabilities to the role as necessary.


  • OpenStack supports encryption technologies such as HTTPS, SSH, SSL, TLS, digital certificates, and data encryption.


  • Alternative term for an API endpoint.

Endpoint Registry

  • Alternative term for a Keystone catalog.

Endpoint Template

  • A list of URL and port number endpoints that indicate where a service (object storage, compute, identity, etc) can be accessed.

Ephemeral Storage

  • A disk or disk subsystem typically local to the Compute Node that doesn't explicitly provide for persistence. Ephemeral Images are placed atop Ephemeral Storage. Changes made to it should not be expect to be saved.

Ephemeral Image

  • A virtual machine image that does not save changes made to it's volumes and reverts them to their original state after the instance is terminated.

Ephemeral Volume

  • Volume that does not save the changes made to it and reverts to it's original state when the current user relinquishes control.


  • Project name for the fifth release of OpenStack.


  • One of the hypervisors supported by OpenStack.


  • One of the hypervisors supported by OpenStack.


  • MD5 hash of an object within Swift, used to ensure data integrity.


  • A collection of command line tools for administring virtual machines, most are compatible with OpenStack.

Eucalyptus Kernel Image (EKI)

  • Used along with an ERI to create an EMI.

Eucalyptus Machine Image (EMI)

  • Virtual machine image container format supported by Glance.

Eucalyptus Ramdisk Image (ERI)

  • Used along with an EKI to create an EMI.


  • The process of migrating one or all virtual machine instances from one host to another, compatible with both shared storage live migration and block migration.


  • Alternative term for a RabbitMQ message exchange.

Exchange Type

  • A routing algorithm in Nova's RabbitMQ.

Exclusive Queue

  • Connected to by a direct consumer in RabbitMQ / Nova, the message can only be consumed by the current connection.

Extended Attributes (xattrs)

  • File system option that allows for storage of additional information beyond owner, group, permissions, modification time and so on.
  • Swift's underlying file system must support extended attributes.


  • Alternative term for a Nova API extension or plug-in.
  • In the context of Keystone this is a call that is specific to the implementation (eg: adding support for OpenID).

Extra Specs

  • Allows additional requirements to be specified when Nova determines where to start a new instance, examples include a minimum amount of network bandwidth or a GPU.


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  • An easy method to create a local LDAP directory for testing Keystone and Nova, requires Redis.

Fan-out Exchange

  • Within RabbitMQ and Nova it is the messaging interface that is used by the scheduler service to receive capability messages from the compute, volume, and network nodes.


  • A Linux distribution compatible with OpenStack.

Fibre Channel

  • Storage protocol similar in concept to TCP/IP, encapsulates SCSI commands and data.

Fibre Channel over Ethernet (FCoE)

  • The fibre channel protocol tunneled within ethernet.

Fill-first Scheduler

  • Nova scheduling method that attempts to fill a host with virtual machines rather than starting new virtual machines on a variety of hosts.


  • The step of the Nova scheduing process where hosts that cannot run the virtual machine(s) are eliminated and will not be chosen.

Filter Definition

  • rootwrap fixfixfix

Filter Type

  • fixfixfix rootwrap


  • Used to restrict communications between hosts and/or nodes, implemented in Nova using iptables, arptables, ip6tables and etables.

Fixed IP Address

  • An IP address that is associated with the same instance each time that instance boots, generally not accessable to end users or the public internet, used for management of the instance.

FlatDHCP Manager

  • Component of Nova that provides dnsmasq (DHCP, DNS, BOOTP, TFTP) and radvd (routing) services.

Flat Manager

  • Component of Nova that gives IP addresses to authorized nodes and assumes DHCP, DNS, and routing configuration and services are provided by something else.

Flat Mode Injection

  • A Nova networking method where the OS network configuration information is injected into the virtual machine image before the instance starts.


  • Alternative term for a virtual machine instance type.

Flavor ID

  • UUID for each Nova / Glance virtual machine flavor or instance type.

Floating IP Address

  • An IP address that a Nova project can associate with one of their virtual machines so the instance has the same public IP address each time it boots.


  • horizon fixfixfix


  • Swift middleware that allows users to upload (post) an image via a form on a web page.


  • Project name for the sixth release of OpenStack.


  • The point where a user interacts with a service, can be an API endpoint, the Horizon dashboard, or a command line tool.


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  • Project name for OpenStack Image Service.

Glance API Server

  • Processes client requests for VMs, updates Glance metadata on the registry server, and communicates with the store adapter to upload VM images from the backend store.

Glance Registry

  • Alternative term for Glance's image registry.

Global Endpoint Template

  • Keystone endpoint template that contains services available to all tenants.


  • A file system designed to aggregate NAS hosts, compatible with OpenStack.

Golden Image

  • A method of operating system installation where a finalized disk image is created and then used by all nodes without modification.

Graphics Processing Unit (GPU)

  • Choosing a host based on the existence of a GPU is currently unsupported in OpenStack.

Green Threads

  • The cooperative threading model used by Python, reduces race conditions, and only context switches when specific library calls are made. Each OpenStack service is it's own thread.


  • Project name for the sixth release of OpenStack.

Guest OS

  • An operating system instance running under the control of a hypervisor.


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  • An object state in Swift where a new replica of the object is automatically created due to a drive failure.

Hard Reboot

  • A type of reboot where a physical or virtual power button is pressed as opposed to a graceful, proper shutdown of the operating system.


  • Project name for OpenStack Dashboard.

Horizon Plugin

  • A plugin for the OpenStack dashboard (Horizon).


  • A physical computer, not a virtual machine instance (node).

Host Aggregate

  • A method to further subdivide availability zones into hypervisor pools, a collection of common hosts.

Host Bus Adapter (HBA)

  • Device plugged into a PCI slot such as a fibre channel or network card.

Hypertext Transfer Protocol Secure (HTTPS)

  • Encrypted HTTP communications using SSL or TLS, most OpenStack API endpoints and many inter-component communications support HTTPS communication.


  • One of the hypervisors supported by OpenStack, actions are underway to add full support.


  • Software that arbitrates and controls virtual machine access to the actual underlying hardware.

Hypervisor Pool

  • A collection of hypervisors grouped together via host aggregates.


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ID Number

  • Unique numeric identifier associated with each user in Keystone, conceptually similar to a Linux or LDAP UID.

Identity API

  • Alternative term for the Identity Service API.

Identity Backend

  • The source used by Keystone to retrieve user information an OpenLDAP server for example.

Identity Service

  • OpenStack's identity service is provided by the Keystone project.

Identity Service API

  • The API used to access Keystone's identity service.


  • A file that contains a complete Linux virtual machine.

Image API

  • Glance's API endpoint for management of virtual machine images.

Image Cache

  • Used by Glance to allow images on the local host to be used rather than re-downloading them from the image server each time one is requested.

Image Identifier

  • Combination of URI and UUID used to access Glance virtual machine images via the image API.

Image Membership

  • A list of tenants that can access a given virtual machine image within Glance.

Image Owner

  • The Keystone tenant who owns a Glance virtual machine image.

Image Registry

  • A list of virtual machine images that are available via Glance.

Image Service API

  • Alternative name for Glance's image API.

Image Status

  • The current status of a virtual machine image in Glance, not to be confused with the status of a running instance.

Image Store

  • The backend store used by Glance to store virtual machine images, options include Swift, local file system, S3, or HTTP.

Image UUID

  • UUID used by Glance to uniquely identify each virtual machine image.

Incubated Project

  • A community project may be elevated to this status and is thenpromoted to a core project.

Ingress Filtering

  • The process of filtering incoming network traffic, supported by Nova.


  • The process of putting a file into a virtual machine image before the instance is started.


  • A running virtual machine.

Instance ID

  • Unique identifier that is specific to each running Nova virtual machine instance.

Instance State

  • The current state of a Nova virtual machine image.

Instance Type

  • Describes the parameters of the various virtual machine images that are available to users, includes parameters such as CPU, storage, and memory.
  • Alternative term for flavor.

Instance Type ID

  • Alternative term for a flavor ID.

Instance UUID

  • Unique identifier assigned to each Nova virtual machine instance.

Interface ID

  • Unique identifier for a Quantum VIF or vNIC in the form of a UUID.


  • One of the virtual machine image disk formats supported by Glance.

IP Address Management (IPAM)

  • The process of automating IP address allocation, deallocation, and management. Currently provided by Nova, Melange, and Quantum but will eventually be folded into Quantum.


  • Used along with arptables, ebtables, and iptables to create firewalls in Nova.


  • Used along with arptables, ebtables, and ip6tables to create firewalls in Nova.


  • Supported by Nova, Quantum, and other components of OpenStack.


  • The SCSI disk protocol tunneled within ethernet, supported by Nova, Swift, and Glance.


  • One of the default roles in Nova's RBAC system, allows the user to quarantine any project's instance.


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JavaScript Object Notation (JSON)

  • One of the supported response formats in OpenStack.


  • Tool used for OpenStack development.


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Kernel-based Virtual Machine (KVM)

  • One of the hypervisors supported by OpenStack.


  • Project name for the OpenStack identity service.


  • A tool to automate system configuration and installation on Red Hat, Fedora, and CentOS based Linux distributions.


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Large Object

  • An object within Swift that is larger than 5 gigabytes.


  • OpenStack's collaboration site.


  • Virtualization API library used by OpenStack to interact with many of it's supported hypervisors.

Linux Bridge

  • Software used to allow multiple virtual machines to share a single physical NIC within Nova.

Linux Bridge Quantum Plug-in

  • Plugin that allows a Linux Bridge to understand Quantum's port, interface attachment, and other abstractions.

Linux Containers (LXC)

  • One of the hypervisors supported by OpenStack.

Live Migration

  • The ability within Nova to move running virtual machine instances from one host to another with only a small service interruption during switch-over.

Load Balancing

  • The process of spreading client reuqests between two or more nodes in order to improve performance and availability.


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Management API

  • Alternative term for an admin API.

Management Network

  • A network segment used for administration, not accessable to the public internet.


  • Logical groupings of related code such as Nova's volume manager or network manager.


  • Used to track segements of a large object within Swift.

Manifest Object

  • A special Swift object that contains a large object's manifest.

Meta-Data Server (MDS)

  • Stores CephFS metadata.


  • Project name for OpenStack Network Information Service, will be merged with Quantum.


  • The association between a Glance virtual machine image and a tenant, allows images to be shared with specified tenant(s).

Membership List

  • Contains a list of tenants that can access a given virtual machine image within Glance.


  • A distributed memory object caching system, used by Swift for caching.

Memory Overcommit

  • Alternative term for RAM overcommit.

Message Broker

  • The software package used to provide AMQP messaging capabilities within Nova, default is RabbitMQ.

Message Bus

  • The main virtual communication line used by all AMQP messages for inter-cloud communications within Nova.

Message Exchange

  • rabbitmq nova fixfixfix

Message Queue

  • Passes requests from clients to the appropriate workers and returns the output to the client once the job is complete.


  • The process of moving a virtual machine instance from one host to another.

Monitor (Mon)

  • Component of Ceph that communicates with external clients, checks data state and consistency, and performs quorum functions.

Multi-factor Authentication

  • Authentication using two or more sources such as a password and a private key, currently unsupported in Keystone.


  • Facility in Nova that allows each virtual machine instance to have more than one VIF connected to it.


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  • Released as open source by NASA in 2010 and is the basis for Nova.


  • One of the default roles in Nova's RBAC system, allows the user to allocate publicly accessable IP addresses to instances and change firewall rules.

NetApp Volume Driver

  • Allows Cinder to communicate with NetApp storage devices via variety of deployment options. NetApp's clustered Data ONTAP and 7-mode are provided for along with options to either establish a direct relationship or mediate it via NetApp OnCommand. Additionally, both iSCSI and NFS are supported as a means of underpinning Cinder Volumes.

Network Address Translation (NAT)

  • The process of modifying IP address information while in-transit, supported by Nova and Quantum.

Network Controller

  • Nova daemon that orchestrates the network configuration of nodes including includes IP addresses, VLANs, bridging, and manages routing for both public interfaces and private interfaces.

Network File System (NFS)

  • A method for making file systems available over the network, supported, in part, by OpenStack. Both a Cinder reference driver implementation and a NetApp specific option are available for underpinning Cinder Volumes. While Cinder remains a block storage service, storage is vended to the Compute Node via NFS whereupon files are treated as the basis for and represented as virtual block devices up through the hypervisor. Additionally, NFS has commonly been deployed as a means of establishing persistence, portability, and support greater Instance availability. In this case NFS is mounted to /var/lib/nova/instances/ (the default location Ephemeral Images are copied to on Compute Nodes.)

Network ID

  • Unique identifier assigned to each network segement within Quantum.

Network Manager

  • Component of Nova that manages various network components (firewall rules, IP address allocation, etc).

Network Node

  • Any Nova node that runs the network worker daemon.

Network Segment

  • Represents a virtual, isolated OSI layer 2 subnet in Quantum.

Network Time Protocol (NTP)

  • A method of keeping a host's or node's clock correct via communications with a trusted, accurate time source.

Network UUID

  • Unique identifier for a Quantum network segment.

Network Worker

  • The nova-network worker daemon, provides services such as giving an IP address to a booting Nova instance.

Nexenta Volume Driver

  • Provides support for NexentaStor devices in Nova.

Nicira NVP Quantum Plugin

  • Provides support for Nicira's Network Virtualization Platform (NVP) in Quantum.


  • Disables server-side message acknowledgement in Nova's RabbitMQ, increases performance but decreases reliability.


  • A virtual machine instance running on a host.

non-Durable Exchange

  • Message exchange that is cleared when the service restarts, it's data is not written to persistent storage.

non-Durable Queue

  • Message queue that is cleared when the service restarts, it's data is not written to persistent storage.

non-Persistent Volume

  • Alternative term for an ephemeral volume.


  • Project name for OpenStack Compute.

Nova API

  • Alternative term for Nova's compute API.

Nova Network

  • Component of Nova that manages IP address allocation, firewalling, and other network related tasks.

Nova Volume

  • The component of Nova that manages storage volumes, currently being split off into a separate project named Cinder.


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  • A BLOB of data held by Swift, can be in any format.

Object API

  • Alternative term for the Swift object API.

Object Auditor

  • Opens all of an object server's objects and verifies the MD5 hash, size, and metadata of each.

Object Expiration

  • A configurable option within Swift to automatically delete objects after a specified amount of time has passed or a certain date is reached.

Object Hash

  • Uniquely identifier for a Swift object.

Object Path Hash

  • Used by Swift to determine object's location within the ring, maps objects to partitions.

Object Replicator

  • Component of Swift that copies and object to remote partitions for fault tolerance.

Object Service API

  • Alternative term for Swift's object API.

Object Server

  • Component of Swift that is responsible for managing objects.

Object Versioning

  • Allows a user to set a flag on a Swift container so all objects within the container are versioned.


  • Term for a Swift process that has been running for a long time, may be an indication of a hung process.


  • Currently unsupported in OpenStack.


  • An open source LDAP server, supported by both Nova and Keystone.

OpenStack API (OSAPI)

  • The core OpenStack API.


  • A Linux distribution that is compatible with OpenStack.

Open Cloud Computing Interface (OCCI)

  • A standardized interface for managing compute, data, and network resources, currently unsupported in OpenStack.

Open Virtualization Format (OVF)

  • Standard for packaging virtual machine images, supported in OpenStack.

Open vSwitch (OVS)

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Open vSwitch Quantum Plug-in

  • A plugin for Quantum used to provide support for Open vSwitch.


  • In the context of Swift this is a process that is not terminated after an upgrade, restart, or reload of the service.

Object Storage Device OSD

  • The Ceph storage daemon.


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  • horizon fixfixfix

Panel Class

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Parent Cell

  • If a requested resource (CPU time, disk storage, memory) is not available in the parent cell, the request is forwarded to it's associated child cell(s).


  • A unit of storage within Swift used to store objects, exists on top of devices, replicated for fault tolerance.

Partition Index

  • Contains the locations of all Swift partitions within the ring.

Partition Power

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Partition Shift Value

  • Used by Swift to detemrine which partition data should reside on.


  • A virtual machine state where no changes occur (no changes in memory, network communications stop, etc), the virtual machine is frozen but not shut down.

PCI Passthrough

  • Allows guest virtual machines to have exclusive access to a PCI device, currently unsupported in OpenStack.

Persistent Message

  • A message that is stored both in memory and on disk, the message is not lost after a failure or restart.

Persistent Volume

  • Changes to these types of disk volumes are saved.

Personality File

  • A file used to customize a Nova instance, can be used to inject SSH keys or a specific network configuration.


  • fixfixfix


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Policy Service

  • Component of Keystone that provides a rule management interface and a rule based authorization engine.


  • A virtual network port within Quantum, VIFs / vNICs are connected to a port.


  • Unique identifier for a Quantum port.


  • A tool to automate system configuration and installation on Debian based Linux distributions.

Public Dashboard

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Private Image

  • Glance virtual machine images that are only available to specified tenants.

Private IP Address

  • An IP address used for management and administration, not available to the public internet.

Private Key

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  • A logical grouping of users within Nova, used to define quotas and access to virtual machine images.

Project ID

  • User defined alpha-numeric string in Nova, the name of a project.

Project VPN

  • Alternative term for a cloudpipe.


  • Nova term that describes an administrator who has access to all hosts and instances.

Proxy Node

  • A node that provides the Swift proxy service.

Proxy Server

  • Users of Swift interact with the service via the proxy server which in-turn looks up the location of the requested data within the ring and returns the results to the user.

Public API

  • An API endpoint used for both service to service communication and end user interactions.

Public Image

  • A Glance virtual machine image that is available to all tenants.

Public IP Address

  • An IP address that is accessable to end-users.

Public Key

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Public URL

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  • An operating system configuration management tool supported by OpenStack.


  • Programming language used extensively in OpenStack.


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QEMU Copy On Write 2 (QCOW2)

  • One of the virtual machine image disk formats supported by Glance.


  • Message queue software supported by OpenStack, an alternative to RabbitMQ.


  • Project name for OpenStack network.

Quantum API

  • API used to access Quantum, provides and extensible architecture to allow custom plugin creation.

Quantum Manager

  • Allows Nova and Quantum integration thus allowing Quantum to perform network management for Nova virtual machines.

Quantum Plugin

  • Interface within Quantum that allows organizations to create custom plugins for advanced features such as QoS, ACLs, or IDS.


  • If Swift finds objects, containers, or accounts that are corrupt they are placed in this state, are not replicated, cannot be read by clients, and a correct copy is re-replicated.


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Queue Element

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Quick EMUlator (QEMU)

  • One of the hypervisors supported by OpenStack, generally used for development purposes.


  • Nova provides the ability to set resource limits on a per-project basis.


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  • The default message queue software used by OpenStack.

Rackspace Cloud Files

  • Released as open source by Rackspace in 2010, the basis for Swift.

Reliable, Autonomic Distributed Object Store (RADOS)

  • A collection of components that provides object storage within Ceph, similar to Swift.


  • The router advertisement daemon, used by Nova's VLAN manager and FlatDHCP manager to provide routing services for virtual machine instances.

RAM Filter

  • Nova setting that allows or disallows RAM overcommitment.

RAM Overcommit

  • The ability to start new virtual machine instances based on a host's actual memory usage as opposed to basing the decision on the amount of RAM each running instance thinks it has available.

Rate Limit

  • Configurable option within Swift to limit database writes on a per-account and/or per-container basis.


  • One of the virtual machine image disk formats supported by Glance, an unstructured disk image.

RADOS Block Device (RBD)

  • Component of Ceph that allows a Linux block device to be striped over multiple distributed data stores.


  • The process of distributing Swift partitions across all drives in the ring, used during initial ring creation and after ring reconfiguration.


  • The process of shutting down a Nova instance and re-creating it using a virtual machine image.


  • A component of Swift used to collect metrics.

Record ID

  • A number within a database that is incremented each time a change is made, used by Swift when replicating.

Red Hat Enterprise Linux (RHEL)

  • A Linux distribution that is compatible with OpenStack.

Red Dwarf Lite

  • Community project that aims to provide database as a service.


  • keystone and nova. context fixfixfix


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  • Alternative term for the Glance image registry.

Registry Server

  • Glance service that provides virtual machine image metadata information to clients.

Remote Procedure Call (RPC)

  • The method used by Nova's RabbitMQ for intra-service communications.


  • The process of modifying a Nova virtual machine instance's resources (usually RAM).


  • The process of copying data to a seprate physical device for fault tolerance and performance.


  • Swift's backend process that creates and manages object replicas.


  • Provides data redundancy and fault tolerance by creating copies of Swift objects, accounts, and containers so they are not lost when the underlying storage fails.

Replica Count

  • The number of replicas of the data within a Swift ring.

Request ID

  • Unique identifier assigned to each request sent to Nova.


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Reseller Admin

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Rescue Image

  • A special type of virtual machine image that is booted when an instance is placed into rescue mode, allows an administrator to mount the problematic instance's file systems to correct the problem.


  • An entity that maps Swift data to partitions, there is a separate ring for each service (account, object, and container).

Ring Builder

  • Builds and manages rings within Swift, assigns partitions to devices, and pushes the configuration to other storage nodes.

Role Based Access Control (RBAC)

  • Provides a pre-defined list of actions the user can take (start or stop virtual machines, reset passwords, etc), supported in both Keystone and Nova and can be configured using the Horizon dashboard.

Role ID

  • Alpha-numeric identifier assigned to each Keystone role.


  • A feature of Nova that allows the unpriviledged "nova" user to run a specified list of commands as the Linux root user.

RPC Driver

  • Modular system that allows Nova's underlying message queue software to be changed (eg: from RabbitMQ to ZeroMQ or Qpid).

Round-robin Scheduler

  • Type of Nova scheduler that evenly distributes instances among available hosts.

Routing Key

  • Nova's direct exchanges, fanout exchanges, and topic exchanges use this to determine how to process a message, processing varies depending on exchange type.


  • Used by Swift to push object replicas.


  • Absolute limit on the amount of network traffic a Nova virtual machine instance can send and receive.

RXTX Quota

  • Soft limit on the amount of network traffic a Nova virtual machine instance can send and receive.

Ryu Quantum Plugin

  • Allows the Ryu Network Operating System to function as a Quantum OpenFlow controller.


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  • Object storage service by Amazon, similar in function to Swift, can act as a backend store for Glance virtual machine images.

Scheduler Manager

  • Component of Nova's that determines where virtual machine instances should start, uses modular design to support a variety of scheduler types.

Scheduler Service

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Scoped Token

  • A Keystone API access token that is associated with a specific tenant.


  • Checks for and deletes unused virtual machine, the component of Glance that implements delayed delete.

Secret Key

  • String of text only known by the user, used along with an access key to make requests to Nova's API.

Secure Shell (SSH)

  • Open source tool used to access remote hosts via an encrypted communications channel, SSH key injection is supported by Nova.

Security Assertion Markup Language (SAML)

  • fixfixfix, supported by Nova and Cinder.

Security Group

  • A set of network traffic filtering rules that are applied to a Nova instance.

Segmented Object

  • A Swift large object that has been broken up into pieces, the re-assembled object is called a concatenated object.

Server Image

  • Alternative term for a virtual machine image.

Server UUID

  • Unique identifier assigned to each Nova virtual machine instance.

Service Catalog

  • Alternative term for Keystone's catalog.

Service ID

  • Unique identifier assigned to each service that is available in Keystone's catalog.

Service Registration

  • Feature of Keystone that allows services such as Nova to automatically register with the catalog.

Service Tenant

  • Special Keystone tenant that contains all services listed in the catalog.

Service Token

  • An administrator defined token used by Nova to communicate securely with Keystone.

Session Backend

  • The method of storage used by Horizon to track client sessions such as local memory, cookies, a database, or memcached.

Session Storage

  • Component of Horizon that stores and tracks client session information, implemented via Django's sessions framework.

Settings Dashboard

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Shared IP Address

  • An IP address that can be assigned to a virtual machine instance within the shared IP group.

Shared IP Group

  • A group of servers that can share public IP addresses with other members of the group.

Shared Queue

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Shared Storage

  • Block storage that is simultaneously accessable by multiple clients, an example is NFS.


  • Distributed block storage system for QEMU, supported by OpenStack.

Simple Cloud Identity Management (SCIM)

  • Specification for managing identity in the cloud, currently unsupported by OpenStack.

Simple Scheduler

  • Volume scheduler type within Nova, deprecated in Folsom release.

Single-root I/O Virtualization (SR-IOV)

  • Alternative term for PCI passthrough, currently unsupported in OpenStack.

SUSE Linux Enterprise Server (SLES)

  • A Linux distribution that is compatible with OpenStack.


  • fixfixfix horizon


  • Runs automated tests against the core OpenStack API, written in Rails.


  • A point-in-time copy of a storage volume, supported by OpenStack.

Soft Reboot

  • A controlled reboot where a virtual machine instance is properly restarted via operating system commands.

SolidFire Volume Driver

  • Nova volume driver for the SolidFire iSCSI storage appliance.

Spread-first Scheduler

  • Nova virtual machine scheduling algorithm that attempts to start new virtual machines on the host with the least amount of load.


  • An open source SQL toolkit for Python, used in OpenStack.


  • A lightweight SQL database, used as the default persistent storage method in many OpenStack services.


  • Community project that captures Nova AMQP communications, useful for debugging.


  • WSGI middleware component of Swift that serves container data as a static web page.

Static IP Address

  • Alternative term for a fixed IP address.

Storage Backend

  • The method that a service uses for persistent storage such as iSCSI, NFS, or local disk.

Storage Manager

  • Component of XenAPI that provides a pluggable interface in order to support a wide variety of persistent storage backends.

Storage Manager Backend

  • A persistent storage method supported by XenAPI such as iSCSI or NFS.

Storage Node

  • A Swift node that provides container services, account services, and object services, controls the account databaseses, container databases, and object storage.

Storage Services

  • Collective name for Swift's object services, container services, and account services.


  • Specifies the authentication source used by Glance or Keystone.


  • Alternative term for a paused virtual machine instance.


  • Disk based virtual memory, used by operating systems to provide more memory than is actually available on the system.


  • An authentication and authorization service for Swift, implemented via WSGI middleware, uses Swift itself as the persistent backing store.


  • Project name for OpenStack object storage.

Swift All in One (SAIO)

  • Creates a full Swift development environment within a single virtual machine.

Swift Middleware

  • Collective term for components within Swift that allows for additional functionality.

Sync Point

  • Point in time since the last container and accounts database sync among nodes within Swift.


  • One of the default roles in Nova's RBAC system, allows the user add other users to his or her project, interact with virtual machine images that are associated with the project, and start and stop virtual machine instances.


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System Dashboard

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System Usage

  • A component of Nova that along with the notification system collects metrics and usage information, can be used for billing.


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Tab Group

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Tab View

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  • An authentication facility within Swift that allows Swift itself to perform authentication and authorization, frequently used in testing and development.


  • Automated software test suite designed to run against the OpenStack core project's trunk.


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Template Tag

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  • A component of Swift's middleware that allows a user to create URLs for temporary object access.


  • A group of users, used to isolate access to Nova resources, an alternative term for a Nova project.

Tenant API

  • An API that is accessable to tenants.

Tenant Endpoint

  • A Keystone API endpoint that is associated with one or more tenants.

Tenant ID

  • Unique identifier assigned to each tenant within Keystone, Nova's project IDs map to Keystone's tenant IDs.


  • An alpha-numeric string of text used to access OpenStack APIs and resources.

Token Services

  • Component of Keystone that both manages and validates tokens after a user or tenant has been authenticated.


  • Used to mark Swift objects that have been deleted, ensures the object is not updated on another node after it has been deleted.


  • rabbitmq nova fixfixfix

Topic Consumer

  • nova rabbitmq fixfixfix

Topic Exchange

  • nova rabbitmq fixfixfix

Topic Publisher

  • A process that is created when a RPC call is executed, used to push the message to the topic exchange.


  • Community project used to run automated tests against the OpenStack API.

Transaction ID

  • Unique identifier assigned to each Swift request, used for debugging and tracing.


  • Alternative term for non-durable.

Transient Message

  • A message that is stored in memory and is lost after the server is restarted.

Transient Exchange

  • Alternative term for a non-durable exchange.

Transient Queue

  • Alternative term for a non-durable queue.


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  • A Linux distribution that is compatible with OpenStack.


  • horizon fixfixfix

Unscoped Token

  • Alternative term for a Keystone default token.


  • Collective term for a group of Swift components that process queued and failed updates for containers and objects.


  • In Keystone each user is associated with one or more tenants, and in Nova they can be associated with roles, projects, or both.

User Dashboard

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User Mode Linux (UML)

  • One of the hypervisors supported by OpenStack.


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  • Unique identifier assigned to each Quantum VIF.


  • One of the hypervisors supported by OpenStack.

Virtual Central Processing Unit (vCPU)

  • Allows physical CPUs to be sub-divided and those divisions are then used by instances.

Virtual Disk Image (VDI)

  • One of the virtual machine image disk formats supported by Glance.

Virtual Hard Disk (VHD)

  • One of the virtual machine image disk formats supported by Glance.

Virtual Network Interface (VIF)

  • In Quantum VIFs are assigned to nodes are then attached to a port.
  • Term for a virtual interface in Nova's MultiNic, each represents a separate network with it's own distinct IP address range.

Virtual Machine

  • An operating system instance running on top of a hypervisor, multiple VMs can run at the same time on the same physical host.

Virtual Machine Disk (VMDK)

  • One of the virtual machine image disk formats supported by Glance.

Virtual Machine Image

  • Alternative term for an image.

Virtual Network

  • A L2 network segement within Quantum.

Virtual Network Interface Card (vNIC)

  • fixfixfix quanatum

Virtual Port

  • Attachment point where a virtual interface connects to a virtual network.

Virtual Private Network (VPN)

  • Provided by Nova in the form of cloudpipes.

Virtual Server

  • Alternative term for a virtual machine or guest.

Virtual Storage Array (VSA)

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VLAN Manager

  • Component of Nova that provides dnsmasq, radvd, and sets up forwarding to and from cloudpipe instances.

Virtual Machine Remote Control (VMRC)

  • Method to access virtual machine instance consoles using a web browser, suppored by Nova.

Virtual Network Computing (VNC)

  • Open source GUI and CLI tools used for remote console access to virtual machines, supported by Nova.

Virtual Switch (vSwitch)

  • Software that runs on a host or node and provides the features and functions of a hardware based network switch.

Virtual VLAN

  • Alternative term for a virtual network.

VMware API

  • Nova supports interaction with VMware products via this API.

VNC Proxy

  • Nova component that provides users access to the consoles of their virtual machine instances via VNC or VMRC.


  • Disk-based data storage generally represented as an iSCSI target with a file system that supports extended attributes, can be persistent or ephemeral.

Volume API

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Volume Controller

  • Component of Nova that oversees and coordinates storage volume actions.

Volume Driver

  • Alternative term for a volume plugin.

Volume ID

  • Unique identifer applied to each storage volume under Nova's control.

Volume Manager

  • Component of Nova that creates, attaches, and detatches persistent storage volumes.

Volume Node

  • A Nova node that runs the nova-volume daemon.

Volume Plugin

  • A plugin for Nova's volume manager, provides support for a new and specialized types of backend storage.

Volume Service API

  • Alternative term for the Nova volume API.

Volume Worker

  • The component of Nova that interacts with backend storage to manage the creation and deletion of volumes and the creation of compute volumes, provided by the nova-volume daemon.


  • vSphere is the term used to describe the combination of vCenter and ESXi. ESXi is the hypervisor while vCenter is a light-weight management tool that allows hypervisors to coordinate with each other in distributed clusters while appearing as a single host from the outside. Because vCenter's API is a proper super-set of ESXi's API the two are referred to as vSphere when used together.


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Weighted Cost

  • The sum of each cost used when deciding where to start a new virtual machine instance in Nova.


  • Nova uses this process to determine how suited a job's VM instance(s) are to a particular host (not enough RAM on the host, too many CPUs on the host, etc).


  • Used by Swift storage devices to determine which storage device(s) are suitable for the job, devices are weighted by size.


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  • A daemon that carries out tasks, for example the nova-volume worker attaching storage to an virtual machine instance. Workers listen to a queue and take action when new messages arrive.


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  • One of the hypervisors supported by OpenStack.


  • One of the hypervisors supported by OpenStack.


  • Xen's administrative API, supported by Nova.

Xen Cloud Platform (XCP)

  • One of the hypervisors supported by OpenStack.

Xen Storage Manager Volume Driver

  • A Nova volume plugin that allows for communication with Xen's Storage Manager API.


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  • Greeting used when Homer Simpson answers the phone.


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Zero MQ

  • Message queue software supported by OpenStack, an alternative to RabbitMQ.


  • Tool used in OpenStack development to ensure correctly ordered testing of changes in parallel.

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