This glossary offers a list of terms and definitions to define a vocabulary for OpenStack-related concepts.

To add to OpenStack glossary, clone the openstack/openstack-manuals repository and update the source file doc/common/glossary.rst through the OpenStack contribution process.


2023.1 Antelope

The code name for the twenty seventh release of OpenStack. This release is the first release based on the new release identification process which is formed after « year ». »release count within the year » and the name Antelope, a swift and gracious animal, also a type of steam locomotive.

2023.2 Bobcat

The code name for the twenty eighth release of OpenStack.

2024.1 Caracal

The code name for the twenty ninth release of OpenStack.

2024.2 Dalmatian

The code name for the thirtieth release of OpenStack.


A mechanism that allows IPv6 packets to be transmitted over an IPv4 network, providing a strategy for migrating to IPv6.


absolute limit

Impassable limits for guest VMs. Settings include total RAM size, maximum number of vCPUs, and maximum disk size.

access control list (ACL)

A list of permissions attached to an object. An ACL specifies which users or system processes have access to objects. It also defines which operations can be performed on specified objects. Each entry in a typical ACL specifies a subject and an operation. For instance, the ACL entry (Alice, delete) for a file gives Alice permission to delete the file.

access key

Alternative term for an Amazon EC2 access key. See EC2 access key.


The Object Storage context of an account. Do not confuse with a user account from an authentication service, such as Active Directory, /etc/passwd, OpenLDAP, OpenStack Identity, and so on.

account auditor

Checks for missing replicas and incorrect or corrupted objects in a specified Object Storage account by running queries against the back-end SQLite database.

account database

A SQLite database that contains Object Storage accounts and related metadata and that the accounts server accesses.

account reaper

An Object Storage worker that scans for and deletes account databases and that the account server has marked for deletion.

account server

Lists containers in Object Storage and stores container information in the account database.

account service

An Object Storage component that provides account services such as list, create, modify, and audit. Do not confuse with OpenStack Identity service, OpenLDAP, or similar user-account services.


The Compute service provides accounting information through the event notification and system usage data facilities.

Active Directory

Authentication and identity service by Microsoft, based on LDAP. Supported in OpenStack.

active/active configuration

In a high-availability setup with an active/active configuration, several systems share the load together and if one fails, the load is distributed to the remaining systems.

active/passive configuration

In a high-availability setup with an active/passive configuration, systems are set up to bring additional resources online to replace those that have failed.

address pool

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

Address Resolution Protocol (ARP)

The protocol by which layer-3 IP addresses are resolved into layer-2 link local addresses.

admin API

A subset of API calls that are accessible to authorized administrators and are generally not accessible to end users or the public Internet. They can exist as a separate service (keystone) or can be a subset of another API (nova).

admin server

In the context of the Identity service, the worker process that provides access to the admin API.


The person responsible for installing, configuring, and managing an OpenStack cloud.

Advanced Message Queuing Protocol (AMQP)

The open standard messaging protocol used by OpenStack components for intra-service communications, provided by RabbitMQ, Qpid, or ZeroMQ.

Advanced RISC Machine (ARM)

Lower power consumption CPU often found in mobile and embedded devices. Supported by OpenStack.


The Compute service can send alerts through its notification system, which includes a facility to create custom notification drivers. Alerts can be sent to and displayed on the dashboard.


The process of taking a floating IP address from the address pool so it can be associated with a fixed IP on a guest VM instance.

Amazon Kernel Image (AKI)

Both a VM container format and disk format. Supported by Image service.

Amazon Machine Image (AMI)

Both a VM container format and disk format. Supported by Image service.

Amazon Ramdisk Image (ARI)

Both a VM container format and disk format. Supported by Image service.


A project that ports the shell script-based project named DevStack to Python.


Part of the OpenStack Telemetry service; provides alarming functionality.


The Apache Software Foundation supports the Apache community of open-source software projects. These projects provide software products for the public good.

Apache License 2.0

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

Apache Web Server

The most common web server software currently used on the Internet.

API endpoint

The daemon, worker, or service that a client communicates with to access an API. API endpoints can provide any number of services, such as authentication, sales data, performance meters, Compute VM commands, census data, and so on.

API extension

Custom modules that extend some OpenStack core APIs.

API extension plug-in

Alternative term for a Networking plug-in or Networking API extension.

API key

Alternative term for an API token.

API server

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

API token

Passed to API requests and used by OpenStack to verify that the client is authorized to run the requested operation.

API version

In OpenStack, the API version for a project is part of the URL. For example,


A Java program that can be embedded into a web page.

Application Catalog service (murano)

The project that provides an application catalog service so that users can compose and deploy composite environments on an application abstraction level while managing the application lifecycle.

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.

application server

A piece of software that makes available another piece of software over a network.

Application Service Provider (ASP)

Companies that rent specialized applications that help businesses and organizations provide additional services with lower cost.


Tool used for maintaining Address Resolution Protocol packet filter rules in the Linux kernel firewall modules. Used along with iptables, ebtables, and ip6tables in Compute to provide firewall services for VMs.


The process associating a Compute floating IP address with a fixed IP address.

Asynchronous JavaScript and XML (AJAX)

A group of interrelated web development techniques used on the client-side to create asynchronous web applications. Used extensively in horizon.

ATA over Ethernet (AoE)

A disk storage protocol tunneled within Ethernet.


The process of connecting a VIF or vNIC to a L2 network in Networking. In the context of Compute, this process connects a storage volume to an instance.

attachment (network)

Association of an interface ID to a logical port. Plugs an interface into a port.


Provided in Compute through the system usage data facility.


A worker process that verifies the integrity of Object Storage objects, containers, and accounts. Auditors is the collective term for the Object Storage account auditor, container auditor, and object auditor.


The code name for the initial release of OpenStack. The first design summit took place in Austin, Texas, US.

auth node

Alternative term for an Object Storage authorization node.


The process that confirms that the user, process, or client is really who they say they are through private key, secret token, password, fingerprint, or similar method.

authentication token

A string of text provided to the client after authentication. Must be provided by the user or process in subsequent requests to the API endpoint.


The Identity service component that provides authentication services.


The act of verifying that a user, process, or client is authorized to perform an action.

authorization node

An Object Storage node that provides authorization services.


The Identity component that provides high-level authorization services.

Auto ACK

Configuration setting within RabbitMQ that enables or disables message acknowledgment. Enabled by default.

auto declare

A Compute RabbitMQ setting that determines whether 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. Do not confuse with an OpenStack Compute zone or cell.

AWS CloudFormation template

AWS CloudFormation allows Amazon Web Services (AWS) users to create and manage a collection of related resources. The Orchestration service supports a CloudFormation-compatible format (CFN).


back end

Interactions and processes that are obfuscated from the user, such as Compute volume mount, data transmission to an iSCSI target by a daemon, or Object Storage object integrity checks.

back-end catalog

The storage method used by the Identity service catalog service to store and retrieve information about API endpoints that are available to the client. Examples include an SQL database, LDAP database, or KVS back end.

back-end store

The persistent data store used to save and retrieve information for a service, such as lists of Object Storage objects, current state of guest VMs, lists of user names, and so on. Also, the method that the Image service uses to get and store VM images. Options include Object Storage, locally mounted file system, RADOS block devices, VMware datastore, and HTTP.

Backup, Restore, and Disaster Recovery service (freezer)

The project that provides integrated tooling for backing up, restoring, and recovering file systems, instances, or database backups.


The amount of available data used by communication resources, such as the Internet. Represents the amount of data that is used to download things or the amount of data available to download.


Code name of the Key Manager service.


An Image service container format that indicates that no container exists for the VM image.

Bare Metal service (ironic)

The OpenStack service that provides a service and associated libraries capable of managing and provisioning physical machines in a security-aware and fault-tolerant manner.

base image

An OpenStack-provided image.

Bell-LaPadula model

A security model that focuses on data confidentiality and controlled access to classified information. This model divides the entities into subjects and objects. The clearance of a subject is compared to the classification of the object to determine if the subject is authorized for the specific access mode. The clearance or classification scheme is expressed in terms of a lattice.

Benchmark service (rally)

OpenStack project that provides a framework for performance analysis and benchmarking of individual OpenStack components as well as full production OpenStack cloud deployments.


A grouped release of projects related to OpenStack that came out in February of 2011. It included only Compute (nova) and Object Storage (swift). Bexar is the code name for the second release of OpenStack. The design summit took place in San Antonio, Texas, US, which is the county seat for Bexar county.


Information that consists solely of ones and zeroes, which is the language of computers.


A bit is a single digit number that is in base of 2 (either a zero or one). Bandwidth usage is measured in bits per second.

bits per second (BPS)

The universal measurement of how quickly data is transferred from place to place.

block device

A device that moves data in the form of blocks. These device nodes interface the devices, such as hard disks, CD-ROM drives, flash drives, and other addressable regions of memory.

block migration

A method of VM live migration used by KVM to evacuate instances from one host to another with very little downtime during a user-initiated switchover. Does not require shared storage. Supported by Compute.

Block Storage API

An API on a separate endpoint for attaching, detaching, and creating block storage for compute VMs.

Block Storage service (cinder)

The OpenStack service that implements services and libraries to provide on-demand, self-service access to Block Storage resources via abstraction and automation on top of other block storage devices.

BMC (Baseboard Management Controller)

The intelligence in the IPMI architecture, which is a specialized micro-controller that is embedded on the motherboard of a computer and acts as a server. Manages the interface between system management software and platform hardware.

bootable disk image

A type of VM image that exists as a single, bootable file.

Bootstrap Protocol (BOOTP)

A network protocol used by a network client to obtain an IP address from a configuration server. Provided in Compute through the dnsmasq daemon when using either the FlatDHCP manager or VLAN manager network manager.

Border Gateway Protocol (BGP)

The Border Gateway Protocol is a dynamic routing protocol that connects autonomous systems. Considered the backbone of the Internet, this protocol connects disparate networks to form a larger network.


Any client software that enables a computer or device to access the Internet.

builder file

Contains configuration information that Object Storage uses to reconfigure a ring or to re-create it from scratch after a serious failure.


The practice of utilizing a secondary environment to elastically build instances on-demand when the primary environment is resource constrained.

button class

A group of related button types within horizon. Buttons to start, stop, and suspend VMs are in one class. Buttons to associate and disassociate floating IP addresses are in another class, and so on.


Set of bits that make up a single character; there are usually 8 bits to a byte.


cache pruner

A program that keeps the Image service VM image cache at or below its configured maximum size.


An OpenStack grouped release of projects that came out in the spring of 2011. It included Compute (nova), Object Storage (swift), and the Image service (glance). Cactus is a city in Texas, US and is the code name for the third release of OpenStack. When OpenStack releases went from three to six months long, the code name of the release changed to match a geography nearest the previous summit.


One of the RPC primitives used by the OpenStack message queue software. Sends a message and waits for a response.


Defines resources for a cell, including CPU, storage, and networking. Can apply to the specific services within a cell or a whole cell.

capacity cache

A Compute back-end database table that contains the current workload, amount of free RAM, and number of VMs running on each host. Used to determine on which host a VM starts.

capacity updater

A notification driver that monitors VM instances and updates the capacity cache as needed.


One of the RPC primitives used by the OpenStack message queue software. Sends a message and does not wait for a response.


A list of API endpoints that are available to a user after authentication with the Identity service.

catalog service

An Identity service that lists API endpoints that are available to a user after authentication with the Identity service.


Part of the OpenStack Telemetry service; gathers and stores metrics from other OpenStack services.


Provides logical partitioning of Compute resources in a child and parent relationship. Requests are passed from parent cells to child cells if the parent cannot provide the requested resource.

cell forwarding

A Compute option that enables parent cells to pass resource requests to child cells if the parent cannot provide the requested resource.

cell manager

The Compute component that contains a list of the current capabilities of each host 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 POSIX-compatible distributed file system. Compatible with OpenStack.


The POSIX-compliant file system provided by Ceph.

certificate authority (CA)

In cryptography, an entity that issues digital certificates. The digital certificate certifies the ownership of a public key by the named subject of the certificate. This enables others (relying parties) to rely upon signatures or assertions made by the private key that corresponds to the certified public key. In this model of trust relationships, a CA is a trusted third party for both the subject (owner) of the certificate and the party relying upon the certificate. CAs are characteristic of many public key infrastructure (PKI) schemes. In OpenStack, a simple certificate authority is provided by Compute for cloudpipe VPNs and VM image decryption.

Challenge-Handshake Authentication Protocol (CHAP)

An iSCSI authentication method supported by Compute.

chance scheduler

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

changes since

A Compute API parameter that allows downloading changes to the requested item since your last request, instead of downloading a new, fresh set of data and comparing it against the old data.


An operating system configuration management tool supporting OpenStack deployments.

child cell

If a requested resource such as CPU time, disk storage, or memory is not available in the parent cell, the request is forwarded to its associated child cells. If the child cell can fulfill the request, it does. Otherwise, it attempts to pass the request to any of its children.


Codename for Block Storage service.


A minimal Linux distribution designed for use as a test image on clouds such as OpenStack.

Cisco neutron plug-in

A Networking plug-in for Cisco devices and technologies, including UCS and Nexus.

cloud architect

A person who plans, designs, and oversees the creation of clouds.

Cloud Auditing Data Federation (CADF)

Cloud Auditing Data Federation (CADF) is a specification for audit event data. CADF is supported by OpenStack Identity.

cloud computing

A model that enables access to a shared pool of configurable computing resources, such as networks, servers, storage, applications, and services, that can be rapidly provisioned and released with minimal management effort or service provider interaction.

cloud computing infrastructure

The hardware and software components – such as servers, storage, and network and virtualization software – that are needed to support the computing requirements of a cloud computing model.

cloud computing platform software

The delivery of different services through the Internet. These resources include tools and applications like data storage, servers, databases, networking, and software. As long as an electronic device has access to the web, it has access to the data and the software programs to run it.

cloud computing service architecture

Cloud service architecture defines the overall cloud computing services and solutions that are implemented in and across the boundaries of an enterprise business network. Considers the core business requirements and matches them with a possible cloud solution.

cloud controller

Collection of Compute components that represent the global state of the cloud; talks to services, such as Identity authentication, 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.

cloud technology

Clouds are tools of virtual sources orchestrated by management and automation softwares. This includes, raw processing power, memory, network, storage of cloud based applications.


A package commonly installed in VM images that performs initialization of an instance after boot using information that it retrieves from the metadata service, such as the SSH public key and user data.


One of the default roles in the Compute RBAC system. Grants complete system access.


A Windows project providing guest initialization features, similar to cloud-init.


A compute service that creates VPNs on a per-project basis.

cloudpipe image

A pre-made VM image that serves as a cloudpipe server. Essentially, OpenVPN running on Linux.

Clustering service (senlin)

The project that implements clustering services and libraries for the management of groups of homogeneous objects exposed by other OpenStack services.

command filter

Lists allowed commands within the Compute rootwrap facility.

Command-Line Interface (CLI)

A text-based client that helps you create scripts to interact with OpenStack clouds.

Common Internet File System (CIFS)

A file sharing protocol. It is a public or open variation of the original Server Message Block (SMB) protocol developed and used by Microsoft. Like the SMB protocol, CIFS runs at a higher level and uses the TCP/IP protocol.

Common Libraries (oslo)

The project that produces a set of python libraries containing code shared by OpenStack projects. The APIs provided by these libraries should be high quality, stable, consistent, documented and generally applicable.

community project

A project that is not officially endorsed by the OpenStack Technical Commitee. If the project is successful enough, it might be elevated to an incubated project and then to a core project, or it might be merged with the main code trunk.


Reducing the size of files by special encoding, the file can be decompressed again to its original content. OpenStack supports compression at the Linux file system level but does not support compression for things such as Object Storage objects or Image service VM images.

Compute API (nova API)

The nova-api daemon provides access to nova services. Can communicate with other APIs, such as the Amazon EC2 API.

compute controller

The Compute component that chooses suitable hosts on which to start VM instances.

compute host

Physical host dedicated to running compute nodes.

compute node

A node that runs the nova-compute daemon that manages VM instances that provide a wide range of services, such as web applications and analytics.

Compute service (nova)

The OpenStack core project that implements services and associated libraries to provide massively-scalable, on-demand, self-service access to compute resources, including bare metal, virtual machines, and containers.

compute worker

The Compute component that runs on each compute node and manages the VM instance lifecycle, including run, reboot, terminate, attach/detach volumes, and so on. Provided by the nova-compute daemon.

concatenated object

A set of segment objects that Object Storage combines and sends to the client.


In Compute, conductor is the process that proxies database requests from the compute process. Using conductor improves security because compute nodes do not need direct access to the database.


Code name for the Governance service.

consistency window

The amount of time it takes for a new Object Storage object to become accessible to all clients.

console log

Contains the output from a Linux VM console in Compute.


Organizes and stores objects in Object Storage. Similar to the concept of a Linux directory but cannot be nested. Alternative term for an Image service container format.

container auditor

Checks for missing replicas or incorrect objects in specified Object Storage containers through queries to the SQLite back-end database.

container database

A SQLite database that stores Object Storage containers and container metadata. The container server accesses this database.

container format

A wrapper used by the Image service that contains a VM image and its associated metadata, such as machine state, OS disk size, and so on.

Container Infrastructure Management service (magnum)

The project which provides a set of services for provisioning, scaling, and managing container orchestration engines.

container server

An Object Storage server that manages containers.

container service

The Object Storage component that provides container services, such as create, delete, list, and so on.

content delivery network (CDN)

A content delivery network is a specialized network that is used to distribute content to clients, typically located close to the client for increased performance.

continuous delivery

A software engineering approach in which teams produce software in short cycles, ensuring that the software can be reliably released at any time and, when releasing the software, doing so manually.

continuous deployment

A software release process that uses automated testing to validate if changes to a codebase are correct and stable for immediate autonomous deployment to a production environment.

continuous integration

The practice of merging all developers” working copies to a shared mainline several times a day.

controller node

Alternative term for a cloud controller node.

core API

Depending on context, the core API is either the OpenStack API or the main API of a specific core project, such as Compute, Networking, Image service, and so on.

core service

An official OpenStack service defined as core by Interop Working Group. Currently, consists of Block Storage service (cinder), Compute service (nova), Identity service (keystone), Image service (glance), Networking service (neutron), and Object Storage service (swift).


Under the Compute distributed scheduler, this is calculated by looking at the capabilities of each host relative to the flavor of the VM instance being requested.


Data that is only known to or accessible by a user and used to verify that the user is who he says he is. Credentials are presented to the server during authentication. Examples include a password, secret key, digital certificate, and fingerprint.


A Certificate Revocation List (CRL) in a PKI model is a list of certificates that have been revoked. End entities presenting these certificates should not be trusted.

Cross-Origin Resource Sharing (CORS)

A mechanism that allows many resources (for example, fonts, JavaScript) on a web page to be requested from another domain outside the domain from which the resource originated. In particular, JavaScript’s AJAX calls can use the XMLHttpRequest mechanism.


An open source community project by SUSE that aims to provide all necessary services to quickly deploy and manage clouds.

current workload

An element of the Compute 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 project.

customization module

A user-created Python module that is loaded by horizon to change the look and feel of the dashboard.



A process that runs in the background and waits for requests. May or may not listen on a TCP or UDP port. Do not confuse with a worker.

Dashboard (horizon)

OpenStack project which provides an extensible, unified, web-based user interface for all OpenStack services.

data encryption

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

Data loss prevention (DLP) software

Software programs used to protect sensitive information and prevent it from leaking outside a network boundary through the detection and denying of the data transportation.

Data Processing service (sahara)

OpenStack project that provides a scalable data-processing stack and associated management interfaces.

data store

A database engine supported by the Database service.

database ID

A unique ID given to each replica of an Object Storage database.

database replicator

An Object Storage component that copies changes in the account, container, and object databases to other nodes.

Database service (trove)

An integrated project that provides scalable and reliable Cloud Database-as-a-Service functionality for both relational and non-relational database engines.


The process of removing the association between a floating IP address and a fixed IP address. Once this association is removed, the floating IP returns to the address pool.


A Linux distribution that is compatible with OpenStack.


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

default panel

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

default project

New users are assigned to this project if no project is specified when a user is created.

default token

An Identity service token that is not associated with a specific project and is exchanged for a scoped token.

delayed delete

An option within Image service so that an image is deleted after a predefined number of seconds instead of immediately.

delivery mode

Setting for the Compute RabbitMQ message delivery mode; can be set to either transient or persistent.

denial of service (DoS)

Denial of service (DoS) is a short form for denial-of-service attack. This is a malicious attempt to prevent legitimate users from using a service.

deprecated auth

An option within Compute that enables administrators to create and manage users through the nova-manage command as opposed to using the Identity service.


Code name for the DNS service.


A platform that provides a suite of desktop environments that users access to receive a desktop experience from any location. This may provide general use, development, or even homogeneous testing environments.


One of the default roles in the Compute RBAC system and the default role assigned to a new user.

device ID

Maps Object Storage partitions to physical storage devices.

device weight

Distributes partitions proportionately across Object Storage devices based on the storage capacity of each device.


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

DHCP agent

OpenStack Networking agent that provides DHCP services for virtual networks.


A grouped release of projects related to OpenStack that came out in the fall of 2011, the fourth release of OpenStack. It included Compute (nova 2011.3), Object Storage (swift 1.4.3), and the Image service (glance). Diablo is the code name for the fourth release of OpenStack. The design summit took place in the Bay Area near Santa Clara, California, US and Diablo is a nearby city.

direct consumer

An element of the Compute RabbitMQ that comes to life when a RPC call is executed. It connects to a direct exchange through a unique exclusive queue, sends the message, and terminates.

direct exchange

A routing table that is created within the Compute 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.

Discretionary Access Control (DAC)

Governs the ability of subjects to access objects, while enabling users to make policy decisions and assign security attributes. The traditional UNIX system of users, groups, and read-write-execute permissions is an example of DAC.

disk encryption

The ability to encrypt data at the file system, disk partition, or whole-disk level. Supported within Compute VMs.

disk format

The underlying format that a disk image for a VM is stored as within the Image service back-end store. For example, AMI, ISO, QCOW2, VMDK, and so on.


In Object Storage, tools to test and ensure dispersion of objects and containers to ensure fault tolerance.

distributed virtual router (DVR)

Mechanism for highly available multi-host routing when using OpenStack Networking (neutron).


A web framework used extensively in horizon.

DNS record

A record that specifies information about a particular domain and belongs to the domain.

DNS service (designate)

OpenStack project that provides scalable, on demand, self service access to authoritative DNS services, in a technology-agnostic manner.


Daemon that provides DNS, DHCP, BOOTP, and TFTP services for virtual networks.


An Identity API v3 entity. Represents a collection of projects, groups and users that defines administrative boundaries for managing OpenStack Identity entities. On the Internet, separates a website from other sites. Often, the domain name has two or more parts that are separated by dots. For example,,,, or Also, a domain is an entity or container of all DNS-related information containing one or more records.

Domain Name System (DNS)

A system by which Internet domain name-to-address and address-to-name resolutions are determined. DNS helps navigate the Internet by translating the IP address into an address that is easier to remember. For example, translating into All domains and their components, such as mail servers, utilize DNS to resolve to the appropriate locations. DNS servers are usually set up in a master-slave relationship such that failure of the master invokes the slave. DNS servers might also be clustered or replicated such that changes made to one DNS server are automatically propagated to other active servers. In Compute, the support that enables associating DNS entries with floating IP addresses, nodes, or cells so that hostnames are consistent across reboots.


The transfer of data, usually in the form of files, from one computer to another.

durable exchange

The Compute RabbitMQ message exchange that remains active when the server restarts.

durable queue

A Compute RabbitMQ message queue that remains active when the server restarts.

Dynamic Host Configuration Protocol (DHCP)

A network protocol that configures devices that are connected to a network so that they can communicate on that network by using the Internet Protocol (IP). The protocol is implemented in a client-server model where DHCP clients request configuration data, such as an IP address, a default route, and one or more DNS server addresses from a DHCP server. A method to automatically configure networking for a host at boot time. Provided by both Networking and Compute.

Dynamic HyperText Markup Language (DHTML)

Pages that use HTML, JavaScript, and Cascading Style Sheets to enable users to interact with a web page or show simple animation.


east-west traffic

Network traffic between servers in the same cloud or data center. See also north-south traffic.

EBS boot volume

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


Filtering tool for a Linux bridging firewall, enabling filtering of network traffic passing through a Linux bridge. Used in Compute along with arptables, iptables, and ip6tables to ensure isolation of network communications.


The Amazon commercial compute product, similar to Compute.

EC2 access key

Used along with an EC2 secret key to access the Compute EC2 API.


OpenStack supports accessing the Amazon EC2 API through Compute.

EC2 Compatibility API

A Compute component that enables OpenStack to communicate with Amazon EC2.

EC2 secret key

Used along with an EC2 access key when communicating with the Compute EC2 API; used to digitally sign each request.

edge computing

Running fewer processes in the cloud and moving those processes to local places.

Elastic Block Storage (EBS)

The Amazon commercial block storage product.


The practice of placing one packet type within another for the purposes of abstracting or securing data. Examples include GRE, MPLS, or IPsec.


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


See API endpoint.

endpoint registry

Alternative term for an Identity service catalog.

endpoint template

A list of URL and port number endpoints that indicate where a service, such as Object Storage, Compute, Identity, and so on, can be accessed.

enterprise cloud computing

A computing environment residing behind a firewall that delivers software, infrastructure and platform services to an enterprise.


Any piece of hardware or software that wants to connect to the network services provided by Networking, the network connectivity service. An entity can make use of Networking by implementing a VIF.

ephemeral image

A VM image that does not save changes made to its 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 its original state when the current user relinquishes control.


A grouped release of projects related to OpenStack that came out in April 2012, the fifth release of OpenStack. It included Compute (nova 2012.1), Object Storage (swift 1.4.8), Image (glance), Identity (keystone), and Dashboard (horizon). Essex is the code name for the fifth release of OpenStack. The design summit took place in Boston, Massachusetts, US and Essex is a nearby city.


An OpenStack-supported hypervisor.


MD5 hash of an object within Object Storage, used to ensure data integrity.


A collection of command-line tools for administering VMs; most are compatible with OpenStack.

Eucalyptus Kernel Image (EKI)

Used along with an ERI to create an EMI.

Eucalyptus Machine Image (EMI)

VM image container format supported by Image service.

Eucalyptus Ramdisk Image (ERI)

Used along with an EKI to create an EMI.


The process of migrating one or all virtual machine (VM) 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 the Compute RabbitMQ.

exclusive queue

Connected to by a direct consumer in RabbitMQ—Compute, the message can be consumed only by the current connection.

extended attributes (xattr)

File system option that enables storage of additional information beyond owner, group, permissions, modification time, and so on. The underlying Object Storage file system must support extended attributes.


Alternative term for an API extension or plug-in. In the context of Identity service, this is a call that is specific to the implementation, such as adding support for OpenID.

external network

A network segment typically used for instance Internet access.

extra specs

Specifies additional requirements when Compute determines where to start a new instance. Examples include a minimum amount of network bandwidth or a GPU.



An easy method to create a local LDAP directory for testing Identity and Compute. Requires Redis.

fan-out exchange

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

federated identity

A method to establish trusts between identity providers and the OpenStack cloud.


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

The Compute scheduling method that attempts to fill a host with VMs rather than starting new VMs on a variety of hosts.


The step in the Compute scheduling process when hosts that cannot run VMs are eliminated and not chosen.


Used to restrict communications between hosts and/or nodes, implemented in Compute using iptables, arptables, ip6tables, and ebtables.

FireWall-as-a-Service (FWaaS)

A Networking extension that provides perimeter firewall functionality.

fixed IP address

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

Flat Manager

The Compute component 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 Compute networking method where the OS network configuration information is injected into the VM image before the instance starts.

flat network

Virtual network type that uses neither VLANs nor tunnels to segregate project traffic. Each flat network typically requires a separate underlying physical interface defined by bridge mappings. However, a flat network can contain multiple subnets.

FlatDHCP Manager

The Compute component that provides dnsmasq (DHCP, DNS, BOOTP, TFTP) and radvd (routing) services.


Alternative term for a VM instance type.

flavor ID

UUID for each Compute or Image service VM flavor or instance type.

floating IP address

An IP address that a project can associate with a VM so that the instance has the same public IP address each time that it boots. You create a pool of floating IP addresses and assign them to instances as they are launched to maintain a consistent IP address for maintaining DNS assignment.


A grouped release of projects related to OpenStack that came out in the fall of 2012, the sixth release of OpenStack. It includes Compute (nova), Object Storage (swift), Identity (keystone), Networking (neutron), Image service (glance), and Volumes or Block Storage (cinder). Folsom is the code name for the sixth release of OpenStack. The design summit took place in San Francisco, California, US and Folsom is a nearby city.


Object Storage middleware that uploads (posts) an image through a form on a web page.


Code name for the Backup, Restore, and Disaster Recovery service.

front end

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



An IP address, typically assigned to a router, that passes network traffic between different networks.

generic receive offload (GRO)

Feature of certain network interface drivers that combines many smaller received packets into a large packet before delivery to the kernel IP stack.

generic routing encapsulation (GRE)

Protocol that encapsulates a wide variety of network layer protocols inside virtual point-to-point links.


Codename for the Image service.

glance API server

Alternative name for the Image API.

glance registry

Alternative term for the Image service image registry.

global endpoint template

The Identity service endpoint template that contains services available to all projects.


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


Part of the OpenStack Telemetry service; provides an indexer and time-series database.

golden image

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

Governance service (congress)

The project that provides Governance-as-a-Service across any collection of cloud services in order to monitor, enforce, and audit policy over dynamic infrastructure.

Graphic Interchange Format (GIF)

A type of image file that is commonly used for animated images on web pages.

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 its own thread.


The code name for the seventh release of OpenStack. The design summit took place in San Diego, California, US and Grizzly is an element of the state flag of California.


An Identity v3 API entity. Represents a collection of users that is owned by a specific domain.

guest OS

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



Apache Hadoop is an open source software framework that supports data-intensive distributed applications.

Hadoop Distributed File System (HDFS)

A distributed, highly fault-tolerant file system designed to run on low-cost commodity hardware.


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


Provides a load balancer for TCP and HTTP-based applications that spreads requests across multiple servers.

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.


The code name for the eighth release of OpenStack. The design summit took place in Portland, Oregon, US and Havana is an unincorporated community in Oregon.

health monitor

Determines whether back-end members of a VIP pool can process a request. A pool can have several health monitors associated with it. When a pool has several monitors associated with it, all monitors check each member of the pool. All monitors must declare a member to be healthy for it to stay active.


Codename for the Orchestration service.

Heat Orchestration Template (HOT)

Heat input in the format native to OpenStack.

high availability (HA)

A high availability system design approach and associated service implementation ensures that a prearranged level of operational performance will be met during a contractual measurement period. High availability systems seek to minimize system downtime and data loss.


Codename for the Dashboard.

horizon plug-in

A plug-in for the OpenStack Dashboard (horizon).


A physical computer, not a VM 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.

hybrid cloud

A hybrid cloud is a composition of two or more clouds (private, community or public) that remain distinct entities but are bound together, offering the benefits of multiple deployment models. Hybrid cloud can also mean the ability to connect colocation, managed and/or dedicated services with cloud resources.

hybrid cloud computing

A mix of on-premises, private cloud and third-party, public cloud services with orchestration between the two platforms.


One of the hypervisors supported by OpenStack.

Any kind of text that contains a link to some other site, commonly found in documents where clicking on a word or words opens up a different website.

Hypertext Transfer Protocol (HTTP)

An application protocol for distributed, collaborative, hypermedia information systems. It is the foundation of data communication for the World Wide Web. Hypertext is structured text that uses logical links (hyperlinks) between nodes containing text. HTTP is the protocol to exchange or transfer hypertext.

Hypertext Transfer Protocol Secure (HTTPS)

An encrypted communications protocol for secure communication over a computer network, with especially wide deployment on the Internet. Technically, it is not a protocol in and of itself; rather, it is the result of simply layering the Hypertext Transfer Protocol (HTTP) on top of the TLS or SSL protocol, thus adding the security capabilities of TLS or SSL to standard HTTP communications. Most OpenStack API endpoints and many inter-component communications support HTTPS communication.


Software that arbitrates and controls VM access to the actual underlying hardware.

hypervisor pool

A collection of hypervisors grouped together through host aggregates.



The code name for the ninth release of OpenStack. The design summit took place in Hong Kong and Ice House is a street in that city.

ID number

Unique numeric ID associated with each user in Identity, conceptually similar to a Linux or LDAP UID.

Identity API

Alternative term for the Identity service API.

Identity back end

The source used by Identity service to retrieve user information; an OpenLDAP server, for example.

identity provider

A directory service, which allows users to login with a user name and password. It is a typical source of authentication tokens.

Identity service (keystone)

The project that facilitates API client authentication, service discovery, distributed multi-project authorization, and auditing. It provides a central directory of users mapped to the OpenStack services they can access. It also registers endpoints for OpenStack services and acts as a common authentication system.

Identity service API

The API used to access the OpenStack Identity service provided through keystone.


Internet Engineering Task Force (IETF) is an open standards organization that develops Internet standards, particularly the standards pertaining to TCP/IP.


A collection of files for a specific operating system (OS) that you use to create or rebuild a server. OpenStack provides pre-built images. You can also create custom images, or snapshots, from servers that you have launched. Custom images can be used for data backups or as « gold » images for additional servers.

Image API

The Image service API endpoint for management of VM images. Processes client requests for VMs, updates Image service metadata on the registry server, and communicates with the store adapter to upload VM images from the back-end store.

image cache

Used by Image service to obtain images on the local host rather than re-downloading them from the image server each time one is requested.

image ID

Combination of a URI and UUID used to access Image service VM images through the image API.

image membership

A list of projects that can access a given VM image within Image service.

image owner

The project who owns an Image service virtual machine image.

image registry

A list of VM images that are available through Image service.

Image service (glance)

The OpenStack service that provides services and associated libraries to store, browse, share, distribute and manage bootable disk images, other data closely associated with initializing compute resources, and metadata definitions.

image status

The current status of a VM image in Image service, not to be confused with the status of a running instance.

image store

The back-end store used by Image service to store VM images, options include Object Storage, locally mounted file system, RADOS block devices, VMware datastore, or HTTP.

image UUID

UUID used by Image service to uniquely identify each VM image.

incubated project

A community project may be elevated to this status and is then promoted to a core project.

Infrastructure Optimization service (watcher)

OpenStack project that aims to provide a flexible and scalable resource optimization service for multi-project OpenStack-based clouds.

Infrastructure-as-a-Service (IaaS)

IaaS is a provisioning model in which an organization outsources physical components of a data center, such as storage, hardware, servers, and networking components. A service provider owns the equipment and is responsible for housing, operating and maintaining it. The client typically pays on a per-use basis. IaaS is a model for providing cloud services.

ingress filtering

The process of filtering incoming network traffic. Supported by Compute.

INI format

The OpenStack configuration files use an INI format to describe options and their values. It consists of sections and key value pairs.


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

Input/Output Operations Per Second (IOPS)

IOPS are a common performance measurement used to benchmark computer storage devices like hard disk drives, solid state drives, and storage area networks.


A running VM, or a VM in a known state such as suspended, that can be used like a hardware server.

instance ID

Alternative term for instance UUID.

instance state

The current state of a guest VM image.

instance tunnels network

A network segment used for instance traffic tunnels between compute nodes and the network node.

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 ID assigned to each guest VM instance.

Intelligent Platform Management Interface (IPMI)

IPMI is a standardized computer system interface used by system administrators for out-of-band management of computer systems and monitoring of their operation. In layman’s terms, it is a way to manage a computer using a direct network connection, whether it is turned on or not; connecting to the hardware rather than an operating system or login shell.


A physical or virtual device that provides connectivity to another device or medium.

interface ID

Unique ID for a Networking VIF or vNIC in the form of a UUID.

Internet Control Message Protocol (ICMP)

A network protocol used by network devices for control messages. For example, ping uses ICMP to test connectivity.

Internet protocol (IP)

Principal communications protocol in the internet protocol suite for relaying datagrams across network boundaries.

Internet Service Provider (ISP)

Any business that provides Internet access to individuals or businesses.

Internet Small Computer System Interface (iSCSI)

Storage protocol that encapsulates SCSI frames for transport over IP networks. Supported by Compute, Object Storage, and Image service.


The abbreviation for input and output.

IP address

Number that is unique to every computer system on the Internet. Two versions of the Internet Protocol (IP) are in use for addresses: IPv4 and IPv6.

IP Address Management (IPAM)

The process of automating IP address allocation, deallocation, and management. Currently provided by Compute, melange, and Networking.


Tool used to set up, maintain, and inspect the tables of IPv6 packet filter rules in the Linux kernel. In OpenStack Compute, ip6tables is used along with arptables, ebtables, and iptables to create firewalls for both nodes and VMs.


Extension to iptables that allows creation of firewall rules that match entire « sets » of IP addresses simultaneously. These sets reside in indexed data structures to increase efficiency, particularly on systems with a large quantity of rules.


Used along with arptables and ebtables, iptables create firewalls in Compute. iptables are the tables provided by the Linux kernel firewall (implemented as different Netfilter modules) and the chains and rules it stores. Different kernel modules and programs are currently used for different protocols: iptables applies to IPv4, ip6tables to IPv6, arptables to ARP, and ebtables to Ethernet frames. Requires root privilege to manipulate.


Codename for the Bare Metal service.

iSCSI Qualified Name (IQN)

IQN is the format most commonly used for iSCSI names, which uniquely identify nodes in an iSCSI network. All IQNs follow the pattern iqn.yyyy-mm.domain:identifier, where “yyyy-mm” is the year and month in which the domain was registered, “domain” is the reversed domain name of the issuing organization, and “identifier” is an optional string which makes each IQN under the same domain unique. For example, “”.


One of the VM image disk formats supported by Image service.


A default role in the Compute RBAC system that can quarantine an instance in any project.



A programming language that is used to create systems that involve more than one computer by way of a network.


A scripting language that is used to build web pages.

JavaScript Object Notation (JSON)

One of the supported response formats in OpenStack.

jumbo frame

Feature in modern Ethernet networks that supports frames up to approximately 9000 bytes.


The code name for the tenth release of OpenStack. The design summit took place in Atlanta, Georgia, US and Juno is an unincorporated community in Georgia.



A network authentication protocol which works on the basis of tickets. Kerberos allows nodes communication over a non-secure network, and allows nodes to prove their identity to one another in a secure manner.

kernel-based VM (KVM)

An OpenStack-supported hypervisor. KVM is a full virtualization solution for Linux on x86 hardware containing virtualization extensions (Intel VT or AMD-V), ARM, IBM Power, and IBM zSeries. It consists of a loadable kernel module, that provides the core virtualization infrastructure and a processor specific module.

Key Manager service (barbican)

The project that produces a secret storage and generation system capable of providing key management for services wishing to enable encryption features.


Codename of the Identity service.


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


The code name for the eleventh release of OpenStack. The design summit took place in Paris, France. Due to delays in the name selection, the release was known only as K. Because k is the unit symbol for kilo and the kilogram reference artifact is stored near Paris in the Pavillon de Breteuil in Sèvres, the community chose Kilo as the release name.


large object

An object within Object Storage that is larger than 5 GB.


The collaboration site for OpenStack.

Layer-2 (L2) agent

OpenStack Networking agent that provides layer-2 connectivity for virtual networks.

Layer-2 network

Term used in the OSI network architecture for the data link layer. The data link layer is responsible for media access control, flow control and detecting and possibly correcting errors that may occur in the physical layer.

Layer-3 (L3) agent

OpenStack Networking agent that provides layer-3 (routing) services for virtual networks.

Layer-3 network

Term used in the OSI network architecture for the network layer. The network layer is responsible for packet forwarding including routing from one node to another.


The code name for the twelfth release of OpenStack. The design summit took place in Vancouver, Canada and Liberty is the name of a village in the Canadian province of Saskatchewan.


Virtualization API library used by OpenStack to interact with many of its supported hypervisors.

Lightweight Directory Access Protocol (LDAP)

An application protocol for accessing and maintaining distributed directory information services over an IP network.


Unix-like computer operating system assembled under the model of free and open-source software development and distribution.

Linux bridge

Software that enables multiple VMs to share a single physical NIC within Compute.

Linux Bridge neutron plug-in

Enables a Linux bridge to understand a Networking port, interface attachment, and other abstractions.

Linux containers (LXC)

An OpenStack-supported hypervisor.

live migration

The ability within Compute to move running virtual machine instances from one host to another with only a small service interruption during switchover.

load balancer

A load balancer is a logical device that belongs to a cloud account. It is used to distribute workloads between multiple back-end systems or services, based on the criteria defined as part of its configuration.

load balancing

The process of spreading client requests between two or more nodes to improve performance and availability.

Load-Balancer-as-a-Service (LBaaS)

Enables Networking to distribute incoming requests evenly between designated instances.

Load-balancing service (octavia)

The project that aims to provide scalable, on demand, self service access to load-balancer services, in technology-agnostic manner.

Logical Volume Manager (LVM)

Provides a method of allocating space on mass-storage devices that is more flexible than conventional partitioning schemes.



Code name for the Containers Infrastructure Management service.

management API

Alternative term for an admin API.

management network

A network segment used for administration, not accessible to the public Internet.


Logical groupings of related code, such as the Block Storage volume manager or network manager.


Used to track segments of a large object within Object Storage.

manifest object

A special Object Storage object that contains the manifest for a large object.


Codename for OpenStack Shared File Systems service.


Responsible for managing Shared File System Service devices, specifically the back-end devices.

maximum transmission unit (MTU)

Maximum frame or packet size for a particular network medium. Typically 1500 bytes for Ethernet networks.

mechanism driver

A driver for the Modular Layer 2 (ML2) neutron plug-in that provides layer-2 connectivity for virtual instances. A single OpenStack installation can use multiple mechanism drivers.


Project name for OpenStack Network Information Service. To be merged with Networking.


The association between an Image service VM image and a project. Enables images to be shared with specified projects.

membership list

A list of projects that can access a given VM image within Image service.


A distributed memory object caching system that is used by Object Storage for caching.

memory overcommit

The ability to start new VM instances based on the actual memory usage of a host, as opposed to basing the decision on the amount of RAM each running instance thinks it has available. Also known as RAM overcommit.

message broker

The software package used to provide AMQP messaging capabilities within Compute. Default package is RabbitMQ.

message bus

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

message queue

Passes requests from clients to the appropriate workers and returns the output to the client after the job completes.

Message service (zaqar)

The project that provides a messaging service that affords a variety of distributed application patterns in an efficient, scalable, and highly available manner, and to create and maintain associated Python libraries and documentation.

Meta-Data Server (MDS)

Stores CephFS metadata.

Metadata agent

OpenStack Networking agent that provides metadata services for instances.


The process of moving a VM instance from one host to another.


Code name for Workflow service.


The code name for the thirteenth release of OpenStack. The design summit took place in Tokyo, Japan. Mitaka is a city in Tokyo.

Modular Layer 2 (ML2) neutron plug-in

Can concurrently use multiple layer-2 networking technologies, such as 802.1Q and VXLAN, in Networking.


Codename for OpenStack Monitoring.

Monitor (LBaaS)

LBaaS feature that provides availability monitoring using the ping command, TCP, and HTTP/HTTPS GET.

Monitor (Mon)

A Ceph component that communicates with external clients, checks data state and consistency, and performs quorum functions.

Monitoring (monasca)

The OpenStack service that provides a multi-project, highly scalable, performant, fault-tolerant monitoring-as-a-service solution for metrics, complex event processing and logging. To build an extensible platform for advanced monitoring services that can be used by both operators and projects to gain operational insight and visibility, ensuring availability and stability.

multi-cloud computing

The use of multiple cloud computing and storage services in a single network architecture.

multi-cloud SDKs

SDKs that provide a multi-cloud abstraction layer and include support for OpenStack. These SDKs are excellent for writing applications that need to consume more than one type of cloud provider, but may expose a more limited set of features.

multi-factor authentication

Authentication method that uses two or more credentials, such as a password and a private key. Currently not supported in Identity.


High-availability mode for legacy (nova) networking. Each compute node handles NAT and DHCP and acts as a gateway for all of the VMs on it. A networking failure on one compute node doesn’t affect VMs on other compute nodes.


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


Codename for the Application Catalog service.



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


One of the default roles in the Compute RBAC system. Enables the user to allocate publicly accessible IP addresses to instances and change firewall rules.

NetApp volume driver

Enables Compute to communicate with NetApp storage devices through the NetApp OnCommand Provisioning Manager.


A virtual network that provides connectivity between entities. For example, a collection of virtual ports that share network connectivity. In Networking terminology, a network is always a layer-2 network.

Network Address Translation (NAT)

Process of modifying IP address information while in transit. Supported by Compute and Networking.

network controller

A Compute daemon that orchestrates the network configuration of nodes, including IP addresses, VLANs, and bridging. Also manages routing for both public and private networks.

Network File System (NFS)

A method for making file systems available over the network. Supported by OpenStack.

network ID

Unique ID assigned to each network segment within Networking. Same as network UUID.

network manager

The Compute component that manages various network components, such as firewall rules, IP address allocation, and so on.

network namespace

Linux kernel feature that provides independent virtual networking instances on a single host with separate routing tables and interfaces. Similar to virtual routing and forwarding (VRF) services on physical network equipment.

network node

Any compute node that runs the network worker daemon.

network segment

Represents a virtual, isolated OSI layer-2 subnet in Networking.

Network Service Header (NSH)

Provides a mechanism for metadata exchange along the instantiated service path.

Network Time Protocol (NTP)

Method of keeping a clock for a host or node correct via communication with a trusted, accurate time source.

network UUID

Unique ID for a Networking network segment.

network worker

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

Networking API (Neutron API)

API used to access OpenStack Networking. Provides an extensible architecture to enable custom plug-in creation.

Networking service (neutron)

The OpenStack project which implements services and associated libraries to provide on-demand, scalable, and technology-agnostic network abstraction.


Codename for OpenStack Networking service.

neutron API

An alternative name for Networking API.

neutron manager

Enables Compute and Networking integration, which enables Networking to perform network management for guest VMs.

neutron plug-in

Interface within Networking that enables organizations to create custom plug-ins for advanced features, such as QoS, ACLs, or IDS.


The code name for the fourteenth release of OpenStack. The design summit took place in Austin, Texas, US. The release is named after « Newton House » which is located at 1013 E. Ninth St., Austin, TX. which is listed on the National Register of Historic Places.

Nexenta volume driver

Provides support for NexentaStor devices in Compute.

NFV Orchestration service (tacker)

OpenStack service that aims to implement Network Function Virtualization (NFV) orchestration services and libraries for end-to-end life-cycle management of network services and Virtual Network Functions (VNFs).


An HTTP and reverse proxy server, a mail proxy server, and a generic TCP/UDP proxy server.


Disables server-side message acknowledgment in the Compute RabbitMQ. Increases performance but decreases reliability.


A VM instance that runs on a host.

non-durable exchange

Message exchange that is cleared when the service restarts. Its data is not written to persistent storage.

non-durable queue

Message queue that is cleared when the service restarts. Its data is not written to persistent storage.

non-persistent volume

Alternative term for an ephemeral volume.

north-south traffic

Network traffic between a user or client (north) and a server (south), or traffic into the cloud (south) and out of the cloud (north). See also east-west traffic.


Codename for OpenStack Compute service.

Nova API

Alternative term for the Compute API.


A Compute component that manages IP address allocation, firewalls, and other network-related tasks. This is the legacy networking option and an alternative to Networking.



A BLOB of data held by Object Storage; can be in any format.

object auditor

Opens all objects for an object server and verifies the MD5 hash, size, and metadata for each object.

object expiration

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

object hash

Unique ID for an Object Storage object.

object path hash

Used by Object Storage to determine the location of an object in the ring. Maps objects to partitions.

object replicator

An Object Storage component that copies an object to remote partitions for fault tolerance.

object server

An Object Storage component that is responsible for managing objects.

Object Storage API

API used to access OpenStack Object Storage.

Object Storage Device (OSD)

The Ceph storage daemon.

Object Storage service (swift)

The OpenStack core project that provides eventually consistent and redundant storage and retrieval of fixed digital content.

object versioning

Allows a user to set a flag on an Object Storage container so that all objects within the container are versioned.


The code name for the fifteenth release of OpenStack. The design summit took place in Barcelona, Spain. Ocata is a beach north of Barcelona.


Code name for the Load-balancing service.


Term for an Object Storage process that runs for a long time. Can indicate a hung process.

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 VM images. Supported in OpenStack.

Open vSwitch

Open vSwitch is a production quality, multilayer virtual switch licensed under the open source Apache 2.0 license. It is designed to enable massive network automation through programmatic extension, while still supporting standard management interfaces and protocols (for example NetFlow, sFlow, SPAN, RSPAN, CLI, LACP, 802.1ag).

Open vSwitch (OVS) agent

Provides an interface to the underlying Open vSwitch service for the Networking plug-in.

Open vSwitch neutron plug-in

Provides support for Open vSwitch in Networking.


OpenDev is a space for collaborative Open Source software development.

OpenDev’s mission is to provide project hosting, continuous integration tooling, and virtual collaboration spaces for Open Source software projects. OpenDev is itself self hosted on this set of tools including code review, continuous integration, etherpad, wiki, code browsing and so on. This means that OpenDev itself is run like an open source project, you can join us and help run the system. Additionally, all of the services run are Open Source software themselves.

The OpenStack project is the largest project using OpenDev.


An open source LDAP server. Supported by both Compute and Identity.


OpenStack is a cloud operating system that controls large pools of compute, storage, and networking resources throughout a data center, all managed through a dashboard that gives administrators control while empowering their users to provision resources through a web interface. OpenStack is an open source project licensed under the Apache License 2.0.

OpenStack code name

Each OpenStack release has a code name. Code names ascend in alphabetical order: Austin, Bexar, Cactus, Diablo, Essex, Folsom, Grizzly, Havana, Icehouse, Juno, Kilo, Liberty, Mitaka, Newton, Ocata, Pike, Queens, Rocky, Stein, Train, Ussuri, Victoria, Wallaby, Xena, Yoga, Zed.

Wallaby was the first code name choosen by a new policy: Code names are choosen by the community following the alphabet, for details see release name criteria.

The Victoria name was the last name where code names are cities or counties near where the corresponding OpenStack design summit took place. An exception, called the Waldon exception, was granted to elements of the state flag that sound especially cool. Code names are chosen by popular vote.

At the same time as OpenStack releases run out of alphabet the Technical Committee changed the naming process to have release number and a release name as an identification code. The release number will be the primary identifier: « year ». »release count within the year » and the name will be used mostly for marketing purposes. The first such release is 2023.1 Antelope. Followed by, respectively, 2023.2 Bobcat, 2024.1 Caracal, 2024.2 Dalmatian.


A Linux distribution that is compatible with OpenStack.


The person responsible for planning and maintaining an OpenStack installation.

optional service

An official OpenStack service defined as optional by Interop Working Group. Currently, consists of Dashboard (horizon), Telemetry service (Telemetry), Orchestration service (heat), Database service (trove), Bare Metal service (ironic), and so on.

Orchestration service (heat)

The OpenStack service which orchestrates composite cloud applications using a declarative template format through an OpenStack-native REST API.


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


Codename for the Common Libraries project.



Part of the OpenStack Telemetry service; provides event storage.

parent cell

If a requested resource, such as CPU time, disk storage, or memory, is not available in the parent cell, the request is forwarded to associated child cells.


A unit of storage within Object Storage used to store objects. It exists on top of devices and is replicated for fault tolerance.

partition index

Contains the locations of all Object Storage partitions within the ring.

partition shift value

Used by Object Storage to determine which partition data should reside on.

path MTU discovery (PMTUD)

Mechanism in IP networks to detect end-to-end MTU and adjust packet size accordingly.


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

PCI passthrough

Gives guest VMs exclusive access to a PCI device. Currently supported in OpenStack Havana and later releases.

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 Compute instance. It can be used to inject SSH keys or a specific network configuration.


The code name for the sixteenth release of OpenStack. The OpenStack summit took place in Boston, Massachusetts, US. The release is named after the Massachusetts Turnpike, abbreviated commonly as the Mass Pike, which is the easternmost stretch of Interstate 90.

Platform-as-a-Service (PaaS)

Provides to the consumer an operating system and, often, a language runtime and libraries (collectively, the « platform ») upon which they can run their own application code, without providing any control over the underlying infrastructure. Examples of Platform-as-a-Service providers include Cloud Foundry and OpenShift.


Software component providing the actual implementation for Networking APIs, or for Compute APIs, depending on the context.

policy service

Component of Identity that provides a rule-management interface and a rule-based authorization engine.

policy-based routing (PBR)

Provides a mechanism to implement packet forwarding and routing according to the policies defined by the network administrator.


A logical set of devices, such as web servers, that you group together to receive and process traffic. The load balancing function chooses which member of the pool handles the new requests or connections received on the VIP address. Each VIP has one pool.

pool member

An application that runs on the back-end server in a load-balancing system.


A virtual network port within Networking; VIFs / vNICs are connected to a port.

port UUID

Unique ID for a Networking port.


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

private cloud

Computing resources used exclusively by one business or organization.

private image

An Image service VM image that is only available to specified projects.

private IP address

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

private network

The Network Controller provides virtual networks to enable compute servers to interact with each other and with the public network. All machines must have a public and private network interface. A private network interface can be a flat or VLAN network interface. A flat network interface is controlled by the flat_interface with flat managers. A VLAN network interface is controlled by the vlan_interface option with VLAN managers.


Projects represent the base unit of “ownership” in OpenStack, in that all resources in OpenStack should be owned by a specific project. In OpenStack Identity, a project must be owned by a specific domain.

project ID

Unique ID assigned to each project by the Identity service.

project VPN

Alternative term for a cloudpipe.

promiscuous mode

Causes the network interface to pass all traffic it receives to the host rather than passing only the frames addressed to it.

protected property

Generally, extra properties on an Image service image to which only cloud administrators have access. Limits which user roles can perform CRUD operations on that property. The cloud administrator can configure any image property as protected.


An administrator who has access to all hosts and instances.

proxy node

A node that provides the Object Storage proxy service.

proxy server

Users of Object Storage interact with the service through 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 cloud

Data centers available to many users over the Internet.

public image

An Image service VM image that is available to all projects.

public IP address

An IP address that is accessible to end-users.

public key authentication

Authentication method that uses keys rather than passwords.

public network

The Network Controller provides virtual networks to enable compute servers to interact with each other and with the public network. All machines must have a public and private network interface. The public network interface is controlled by the public_interface option.


An operating system configuration-management tool supported by OpenStack.


Programming language used extensively in OpenStack.


QEMU Copy On Write 2 (QCOW2)

One of the VM image disk formats supported by Image service.


Message queue software supported by OpenStack; an alternative to RabbitMQ.

Quality of Service (QoS)

The ability to guarantee certain network or storage requirements to satisfy a Service Level Agreement (SLA) between an application provider and end users. Typically includes performance requirements like networking bandwidth, latency, jitter correction, and reliability as well as storage performance in Input/Output Operations Per Second (IOPS), throttling agreements, and performance expectations at peak load.


If Object Storage 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.


The code name for the seventeenth release of OpenStack. The OpenStack summit took place in Sydney, Australia. The release is named after the Queens Pound river in the South Coast region of New South Wales.

Quick EMUlator (QEMU)

QEMU is a generic and open source machine emulator and virtualizer. One of the hypervisors supported by OpenStack, generally used for development purposes.


In Compute and Block Storage, the ability to set resource limits on a per-project basis.



The default message queue software used by OpenStack.

Rackspace Cloud Files

Released as open source by Rackspace in 2010; the basis for Object Storage.

RADOS Block Device (RBD)

Ceph component that enables a Linux block device to be striped over multiple distributed data stores.


The router advertisement daemon, used by the Compute VLAN manager and FlatDHCP manager to provide routing services for VM instances.


Codename for the Benchmark service.

RAM filter

The Compute setting that enables or disables RAM overcommitment.

RAM overcommit

The ability to start new VM instances based on the actual memory usage of a host, as opposed to basing the decision on the amount of RAM each running instance thinks it has available. Also known as memory overcommit.

rate limit

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


One of the VM image disk formats supported by Image service; an unstructured disk image.


The process of distributing Object Storage partitions across all drives in the ring; used during initial ring creation and after ring reconfiguration.


Either a soft or hard reboot of a server. With a soft reboot, the operating system is signaled to restart, which enables a graceful shutdown of all processes. A hard reboot is the equivalent of power cycling the server. The virtualization platform should ensure that the reboot action has completed successfully, even in cases in which the underlying domain/VM is paused or halted/stopped.


Removes all data on the server and replaces it with the specified image. Server ID and IP addresses remain the same.


An Object Storage component that collects meters.


Belongs to a particular domain and is used to specify information about the domain. There are several types of DNS records. Each record type contains particular information used to describe the purpose of that record. Examples include mail exchange (MX) records, which specify the mail server for a particular domain; and name server (NS) records, which specify the authoritative name servers for a domain.

record ID

A number within a database that is incremented each time a change is made. Used by Object Storage when replicating.

Red Hat Enterprise Linux (RHEL)

A Linux distribution that is compatible with OpenStack.

reference architecture

A recommended architecture for an OpenStack cloud.


A discrete OpenStack environment with dedicated API endpoints that typically shares only the Identity (keystone) with other regions.


Alternative term for the Image service registry.

registry server

An Image service that provides VM image metadata information to clients.

Reliable, Autonomic Distributed Object Store


A collection of components that provides object storage within Ceph. Similar to OpenStack Object Storage.

Remote Procedure Call (RPC)

The method used by the Compute RabbitMQ for intra-service communications.


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

replica count

The number of replicas of the data in an Object Storage ring.


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


The Object Storage back-end process that creates and manages object replicas.

request ID

Unique ID assigned to each request sent to Compute.

rescue image

A special type of VM image that is booted when an instance is placed into rescue mode. Allows an administrator to mount the file systems for an instance to correct the problem.


Converts an existing server to a different flavor, which scales the server up or down. The original server is saved to enable rollback if a problem occurs. All resizes must be tested and explicitly confirmed, at which time the original server is removed.


A kind of web service API that uses REST, or Representational State Transfer. REST is the style of architecture for hypermedia systems that is used for the World Wide Web.


An entity that maps Object Storage data to partitions. A separate ring exists for each service, such as account, object, and container.

ring builder

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


The code name for the eightteenth release of OpenStack. The OpenStack summit took place in Vancouver, Canada. The release is named after the Rocky Mountains.


A personality that a user assumes to perform a specific set of operations. A role includes a set of rights and privileges. A user assuming that role inherits those rights and privileges.

Role Based Access Control (RBAC)

Provides a predefined list of actions that the user can perform, such as start or stop VMs, reset passwords, and so on. Supported in both Identity and Compute and can be configured using the dashboard.

role ID

Alphanumeric ID assigned to each Identity service role.

Root Cause Analysis (RCA) service (Vitrage)

OpenStack project that aims to organize, analyze and visualize OpenStack alarms and events, yield insights regarding the root cause of problems and deduce their existence before they are directly detected.


A feature of Compute that allows the unprivileged « nova » user to run a specified list of commands as the Linux root user.

round-robin scheduler

Type of Compute scheduler that evenly distributes instances among available hosts.


A physical or virtual network device that passes network traffic between different networks.

routing key

The Compute direct exchanges, fanout exchanges, and topic exchanges use this key to determine how to process a message; processing varies depending on exchange type.

RPC driver

Modular system that allows the underlying message queue software of Compute to be changed. For example, from RabbitMQ to ZeroMQ or Qpid.


Used by Object Storage to push object replicas.

RXTX cap

Absolute limit on the amount of network traffic a Compute VM instance can send and receive.

RXTX quota

Soft limit on the amount of network traffic a Compute VM instance can send and receive.



Codename for the Data Processing service.

SAML assertion

Contains information about a user as provided by the identity provider. It is an indication that a user has been authenticated.


A virtual space in which new or untested software can be run securely.

scheduler manager

A Compute component that determines where VM instances should start. Uses modular design to support a variety of scheduler types.

scoped token

An Identity service API access token that is associated with a specific project.


Checks for and deletes unused VMs; the component of Image service that implements delayed delete.

secret key

String of text known only by the user; used along with an access key to make requests to the Compute API.

secure boot

Process whereby the system firmware validates the authenticity of the code involved in the boot process.

secure shell (SSH)

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

security group

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

segmented object

An Object Storage large object that has been broken up into pieces. The re-assembled object is called a concatenated object.


For IaaS, ability for a regular (non-privileged) account to manage a virtual infrastructure component such as networks without involving an administrator.


Linux kernel security module that provides the mechanism for supporting access control policies.


Code name for the Clustering service.


Computer that provides explicit services to the client software running on that system, often managing a variety of computer operations. A server is a VM instance in the Compute system. Flavor and image are requisite elements when creating a server.

server image

Alternative term for a VM image.

server UUID

Unique ID assigned to each guest VM instance.


An OpenStack service, such as Compute, Object Storage, or Image service. Provides one or more endpoints through which users can access resources and perform operations.

service catalog

Alternative term for the Identity service catalog.

Service Function Chain (SFC)

For a given service, SFC is the abstracted view of the required service functions and the order in which they are to be applied.

service ID

Unique ID assigned to each service that is available in the Identity service catalog.

Service Level Agreement (SLA)

Contractual obligations that ensure the availability of a service.

service project

Special project that contains all services that are listed in the catalog.

service provider

A system that provides services to other system entities. In case of federated identity, OpenStack Identity is the service provider.

service registration

An Identity service feature that enables services, such as Compute, to automatically register with the catalog.

service token

An administrator-defined token used by Compute to communicate securely with the Identity service.

session back end

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

session persistence

A feature of the load-balancing service. It attempts to force subsequent connections to a service to be redirected to the same node as long as it is online.

session storage

A horizon component that stores and tracks client session information. Implemented through the Django sessions framework.


A remote, mountable file system in the context of the Shared File Systems service. You can mount a share to, and access a share from, several hosts by several users at a time.

share network

An entity in the context of the Shared File Systems service that encapsulates interaction with the Networking service. If the driver you selected runs in the mode requiring such kind of interaction, you need to specify the share network to create a share.

Shared File Systems API

A Shared File Systems service that provides a stable RESTful API. The service authenticates and routes requests throughout the Shared File Systems service. There is python-manilaclient to interact with the API.

Shared File Systems service (manila)

The service that provides a set of services for management of shared file systems in a multi-project cloud environment, similar to how OpenStack provides block-based storage management through the OpenStack Block Storage service project. With the Shared File Systems service, you can create a remote file system and mount the file system on your instances. You can also read and write data from your instances to and from your file system.

shared IP address

An IP address that can be assigned to a VM instance within the shared IP group. Public IP addresses can be shared across multiple servers for use in various high-availability scenarios. When an IP address is shared to another server, the cloud network restrictions are modified to enable each server to listen to and respond on that IP address. You can optionally specify that the target server network configuration be modified. Shared IP addresses can be used with many standard heartbeat facilities, such as keepalive, that monitor for failure and manage IP failover.

shared IP group

A collection of servers that can share IPs with other members of the group. Any server in a group can share one or more public IPs with any other server in the group. With the exception of the first server in a shared IP group, servers must be launched into shared IP groups. A server may be a member of only one shared IP group.

shared storage

Block storage that is simultaneously accessible by multiple clients, for example, 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 Protocol for Independent Computing Environments (SPICE)

SPICE provides remote desktop access to guest virtual machines. It is an alternative to VNC. SPICE is supported by OpenStack.

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

A specification that, when implemented by a physical PCIe device, enables it to appear as multiple separate PCIe devices. This enables multiple virtualized guests to share direct access to the physical device, offering improved performance over an equivalent virtual device. Currently supported in OpenStack Havana and later releases.


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


A point-in-time copy of an OpenStack storage volume or image. Use storage volume snapshots to back up volumes. Use image snapshots to back up data, or as « gold » images for additional servers.

soft reboot

A controlled reboot where a VM instance is properly restarted through operating system commands.

Software Development Kit (SDK)

Contains code, examples, and documentation that you use to create applications in the language of your choice.

Software Development Lifecycle Automation service (solum)

OpenStack project that aims to make cloud services easier to consume and integrate with application development process by automating the source-to-image process, and simplifying app-centric deployment.

Software-defined networking (SDN)

Provides an approach for network administrators to manage computer network services through abstraction of lower-level functionality.

SolidFire Volume Driver

The Block Storage driver for the SolidFire iSCSI storage appliance.


Code name for the Software Development Lifecycle Automation service.

spread-first scheduler

The Compute VM scheduling algorithm that attempts to start a new VM 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.


A set of OpenStack resources created and managed by the Orchestration service according to a given template (either an AWS CloudFormation template or a Heat Orchestration Template (HOT)).


Community project that captures Compute AMQP communications; useful for debugging.

static IP address

Alternative term for a fixed IP address.


WSGI middleware component of Object Storage that serves container data as a static web page.


The code name for the nineteenth release of OpenStack. The OpenStack Summit took place in Berlin, Germany. The release is named after the street Steinstraße in Berlin.

storage back end

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

storage manager

A XenAPI component that provides a pluggable interface to support a wide variety of persistent storage back ends.

storage manager back end

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

storage node

An Object Storage node that provides container services, account services, and object services; controls the account databases, container databases, and object storage.

storage services

Collective name for the Object Storage object services, container services, and account services.


Specifies the authentication source used by Image service or Identity. In the Database service, it refers to the extensions implemented for a data store.


A domain within a parent domain. Subdomains cannot be registered. Subdomains enable you to delegate domains. Subdomains can themselves have subdomains, so third-level, fourth-level, fifth-level, and deeper levels of nesting are possible.


Logical subdivision of an IP network.

SUSE Linux Enterprise Server (SLES)

A Linux distribution that is compatible with OpenStack.


The VM instance is paused and its state is saved to disk of the host.


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


Codename for OpenStack Object Storage service.

swift All in One (SAIO)

Creates a full Object Storage development environment within a single VM.

swift middleware

Collective term for Object Storage components that provide additional functionality.

swift proxy server

Acts as the gatekeeper to Object Storage and is responsible for authenticating the user.

swift storage node

A node that runs Object Storage account, container, and object services.

sync point

Point in time since the last container and accounts database sync among nodes within Object Storage.


One of the default roles in the Compute RBAC system. Enables a user to add other users to a project, interact with VM images that are associated with the project, and start and stop VM instances.

system usage

A Compute component that, along with the notification system, collects meters and usage information. This information can be used for billing.



Code name for the NFV Orchestration service

Telemetry service (telemetry)

The OpenStack project which collects measurements of the utilization of the physical and virtual resources comprising deployed clouds, persists this data for subsequent retrieval and analysis, and triggers actions when defined criteria are met.


An authentication facility within Object Storage that enables Object Storage itself to perform authentication and authorization. Frequently used in testing and development.


Automated software test suite designed to run against the trunk of the OpenStack core project.


An Object Storage middleware component that enables creation of URLs for temporary object access.


A group of users; used to isolate access to Compute resources. An alternative term for a project.

Tenant API

An API that is accessible to projects.

tenant endpoint

An Identity service API endpoint that is associated with one or more projects.

tenant ID

An alternative term for project ID.


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

token services

An Identity service component that manages and validates tokens after a user or project has been authenticated.


Used to mark Object Storage objects that have been deleted; ensures that the object is not updated on another node after it has been deleted.

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.


The code name for the twentieth release of OpenStack. The OpenStack Infrastructure Summit took place in Denver, Colorado, US.

Two Project Team Gathering meetings in Denver were held at a hotel next to the train line from downtown to the airport. The crossing signals there had some sort of malfunction in the past causing them to not stop the cars when a train was coming properly. As a result the trains were required to blow their horns when passing through that area. Obviously staying in a hotel, by trains that are blowing their horns 24/7 was less than ideal. As a result, many jokes popped up about Denver and trains - and thus the release is called train.

transaction ID

Unique ID assigned to each Object Storage request; used for debugging and tracing.


Alternative term for non-durable.

transient exchange

Alternative term for a non-durable exchange.

transient message

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

transient queue

Alternative term for a non-durable queue.


OpenStack-on-OpenStack program. The code name for the OpenStack Deployment program.


Codename for OpenStack Database service.

trusted platform module (TPM)

Specialized microprocessor for incorporating cryptographic keys into devices for authenticating and securing a hardware platform.



A Debian-based Linux distribution.

unscoped token

Alternative term for an Identity service default token.


Collective term for a group of Object Storage components that processes queued and failed updates for containers and objects.


In OpenStack Identity, entities represent individual API consumers and are owned by a specific domain. In OpenStack Compute, a user can be associated with roles, projects, or both.

user data

A blob of data that the user can specify when they launch an instance. The instance can access this data through the metadata service or config drive. Commonly used to pass a shell script that the instance runs on boot.

User Mode Linux (UML)

An OpenStack-supported hypervisor.


The code name for the twenty first release of OpenStack. The OpenStack Infrastructure Summit took place in Shanghai, People’s Republic of China. The release is named after the Ussuri river.



The code name for the twenty second release of OpenStack. The OpenDev + PTG was planned to take place in Vancouver, British Columbia, Canada. The release is named after Victoria, the capital city of British Columbia.

The in-person event was cancelled due to COVID-19. The event is being virtualized instead.


Unique ID assigned to each Networking VIF.

Virtual Central Processing Unit (vCPU)

Subdivides physical CPUs. Instances can then use those divisions.

Virtual Disk Image (VDI)

One of the VM image disk formats supported by Image service.

Virtual Extensible LAN (VXLAN)

A network virtualization technology that attempts to reduce the scalability problems associated with large cloud computing deployments. It uses a VLAN-like encapsulation technique to encapsulate Ethernet frames within UDP packets.

Virtual Hard Disk (VHD)

One of the VM image disk formats supported by Image service.

virtual IP address (VIP)

An Internet Protocol (IP) address configured on the load balancer for use by clients connecting to a service that is load balanced. Incoming connections are distributed to back-end nodes based on the configuration of the load balancer.

virtual machine (VM)

An operating system instance that runs on top of a hypervisor. Multiple VMs can run at the same time on the same physical host.

virtual network

An L2 network segment within Networking.

Virtual Network Computing (VNC)

Open source GUI and CLI tools used for remote console access to VMs. Supported by Compute.

Virtual Network InterFace (VIF)

An interface that is plugged into a port in a Networking network. Typically a virtual network interface belonging to a VM.

virtual networking

A generic term for virtualization of network functions such as switching, routing, load balancing, and security using a combination of VMs and overlays on physical network infrastructure.

virtual port

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

virtual private network (VPN)

Provided by Compute in the form of cloudpipes, specialized instances that are used to create VPNs on a per-project basis.

virtual server

Alternative term for a VM or guest.

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.


An OpenStack-supported hypervisor.


Code name for the Root Cause Analysis service.

VLAN manager

A Compute component that provides dnsmasq and radvd and sets up forwarding to and from cloudpipe instances.

VLAN network

The Network Controller provides virtual networks to enable compute servers to interact with each other and with the public network. All machines must have a public and private network interface. A VLAN network is a private network interface, which is controlled by the vlan_interface option with VLAN managers.

VM disk (VMDK)

One of the VM image disk formats supported by Image service.

VM image

Alternative term for an image.

VM Remote Control (VMRC)

Method to access VM instance consoles using a web browser. Supported by Compute.

VMware API

Supports interaction with VMware products in Compute.

VMware NSX Neutron plug-in

Provides support for VMware NSX in Neutron.

VNC proxy

A Compute component that provides users access to the consoles of their VM instances through 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

Alternative name for the Block Storage API.

volume controller

A Block Storage component that oversees and coordinates storage volume actions.

volume driver

Alternative term for a volume plug-in.

volume ID

Unique ID applied to each storage volume under the Block Storage control.

volume manager

A Block Storage component that creates, attaches, and detaches persistent storage volumes.

volume node

A Block Storage node that runs the cinder-volume daemon.

volume plug-in

Provides support for new and specialized types of back-end storage for the Block Storage volume manager.

volume worker

A cinder component that interacts with back-end storage to manage the creation and deletion of volumes and the creation of compute volumes, provided by the cinder-volume daemon.


An OpenStack-supported hypervisor.



The code name for the twenty third release of OpenStack. Wallabies are native to Australia, which at the start of this naming period was experiencing unprecedented wild fires.


Code name for the Infrastructure Optimization service.


Used by Object Storage devices to determine which storage devices are suitable for the job. Devices are weighted by size.

weighted cost

The sum of each cost used when deciding where to start a new VM instance in Compute.


A Compute process that determines the suitability of the VM instances for a job for a particular host. For example, not enough RAM on the host, too many CPUs on the host, and so on.


A daemon that listens to a queue and carries out tasks in response to messages. For example, the cinder-volume worker manages volume creation and deletion on storage arrays.

Workflow service (mistral)

The OpenStack service that provides a simple YAML-based language to write workflows (tasks and transition rules) and a service that allows to upload them, modify, run them at scale and in a highly available manner, manage and monitor workflow execution state and state of individual tasks.



X.509 is the most widely used standard for defining digital certificates. It is a data structure that contains the subject (entity) identifiable information such as its name along with its public key. The certificate can contain a few other attributes as well depending upon the version. The most recent and standard version of X.509 is v3.


Xen is a hypervisor using a microkernel design, providing services that allow multiple computer operating systems to execute on the same computer hardware concurrently.


The Xen administrative API, which is supported by Compute.

Xen Cloud Platform (XCP)

An OpenStack-supported hypervisor.

Xen Storage Manager Volume Driver

A Block Storage volume plug-in that enables communication with the Xen Storage Manager API.


The code name for the twenty fourth release of OpenStack. The release is named after a fictional warrior princess.


An OpenStack-supported hypervisor.


High-performance 64-bit file system created by Silicon Graphics. Excels in parallel I/O operations and data consistency.



The code name for the twenty fifth release of OpenStack. The release is named after a philosophical school with mental and physical practices from India.



Codename for the Message service.


The code name for the twenty sixth release of OpenStack. The release is named after the pronunciation of the letter Z.


Message queue software supported by OpenStack. An alternative to RabbitMQ. Also spelled 0MQ.


Zuul is an open source CI/CD platform specializing in gating changes across multiple systems and applications before landing a single patch.

Zuul is used for OpenStack development to ensure that only tested code gets merged.