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documentation.suse.com / SUSE OpenStack Cloud Crowbar 9 Documentation / Deployment Guide using Crowbar / Glossary of Terminology and Product Names
Applies to SUSE OpenStack Cloud Crowbar 9

Glossary of Terminology and Product Names


A concept of how services are running on nodes in a High Availability cluster. In an active/active setup, both the main and redundant systems are managed concurrently. If a failure of services occurs, the redundant system is already online, and can take over until the main system is fixed and brought back online.


A concept of how services are running on nodes in a High Availability cluster. In an active/passive setup, one or more services are running on an active cluster node, whereas the passive node stands by. If the active node fails then the services are transferred to the passive node.

Administration Server

Also called Crowbar Administration Node. Manages all other nodes. It assigns IP addresses to them, boots them using PXE, configures them, and provides them the necessary software for their roles. To provide these services, the Administration Server runs Crowbar, Chef, DHCP, TFTP, NTP, and other services.

AMI (Amazon Machine Image)

A virtual machine that can be created and customized by a user. AMIs can be identified by an ID prefixed with ami-.

Availability Zone

An OpenStack method of partitioning clouds. It enables you to arrange OpenStack Compute hosts into logical groups. The groups typically have physical isolation and redundancy from other availability zones, for example, by using separate power supply or network equipment for each zone. When users provision resources, they can specify from which availability zone their instance should be created. This allows cloud consumers to ensure that their application resources are spread across disparate machines to achieve high availability if the hardware fails. Since the Grizzly release, availability zones are implemented via host aggregates.

AWS (Amazon Web Services)

A collection of remote computing services (including Amazon EC2, Amazon S3, and others) that together make up Amazon's cloud computing platform.


A set of Chef cookbooks, templates, and other logic. Used to apply a particular Chef role to individual nodes or a set of nodes.


Code name for Telemetry.


Cells provide a new way to scale Compute deployments. This includes the ability to have compute clusters (cells) in different geographic locations all under the same Compute API. This allows for a single API server being used to control access to multiple cloud installations. Cells provide logical partitioning of Compute resources in a child/parent relationship.


A massively scalable, open source, distributed storage system. It consists of an object store, a block store, and a POSIX-compliant distributed file system.


An automated configuration management platform for deployment of your entire cloud infrastructure. The Chef server manages many of the software packages and allows the easy changing of nodes.


Code name for OpenStack Block Storage.


A package commonly installed in virtual machine images. It uses the SSH public key to initialize an instance after boot.


A set of connected computers that work together. In many respects (and from the outside) they can be viewed as a single system. Clusters can be further categorized depending on their purpose, for example: High Availability clusters, high-performance clusters, or load-balancing clusters.

Cluster Partition

Whenever communication fails between one or more nodes and the rest of the cluster, a cluster partition occurs: The nodes of a cluster are split into partitions but still active. They can only communicate with nodes in the same partition and are unaware of the separated nodes. As the loss of the nodes on the other partition cannot be confirmed, a Split Brain scenario develops.

Cluster Resource Manager

The main management entity in a High Availability cluster responsible for coordinating all non-local interactions. The SUSE Linux Enterprise High Availability Extension uses Pacemaker as CRM. Each node of the cluster has its own CRM instance. The instance running on the Designated Coordinator (DC) is the one elected to relay decisions to the other non-local CRMs and to process their input.

Compute Node

Node within a SUSE OpenStack Cloud. A physical server running a Hypervisor. A Compute Node is a host for guest virtual machines that are deployed in the cloud. It starts virtual machines on demand using nova-compute. To split virtual machine load across more than one server, a cloud should contain multiple Compute Nodes.


A container is a storage compartment for data. It can be thought of as a directory, only that it cannot be nested.

Control Node

Node within a SUSE OpenStack Cloud. The Control Node is configured through the Administration Server and registers with the Administration Server for all required software. Hosts the OpenStack API endpoints and the OpenStack scheduler and runs the nova services—except for nova-compute, which is run on the Compute Nodes. The Control Node coordinates everything about cloud virtual machines: like a central communication center it receives all requests (for example, if a user wants to start or stop a virtual machine). It communicates with the Compute Nodes to coordinate fulfillment of the request. A cloud can contain multiple Control Nodes.


A collection of Chef recipes which deploy a software stack or functionality. The unit of distribution for Chef.


The messaging/infrastructure layer used in a High Availability cluster that is set up with SUSE Linux Enterprise High Availability Extension. For example, the cluster communication channels are defined in /etc/corosync/corosync.conf.


Bare-metal installer and an extension of Chef server. The primary function of Crowbar is to get new hardware into a state where it can be managed by Chef. That means: Setting up BIOS and RAID, network, installing a basic operating system, and setting up services like DNS, NTP, and DHCP. The Crowbar server manages all nodes, supplying configuration of hardware and software.

Designated Coordinator (DC)

One Cluster Resource Manager in a High Availability cluster is elected as the Designated Coordinator (DC). The DC is the only entity in the cluster that can decide that a cluster-wide change needs to be performed. For example, fencing a node or moving resources around. After a membership change, the DC is elected from all nodes in the cluster.

DRBD (Distributed Replicated Block Device)

DRBD is a block device designed for building high availability clusters. The whole block device is mirrored via a dedicated network and is seen as a network RAID-1.

EBS (Amazon Elastic Block Store)

Block-level storage volumes for use with Amazon EC2 instances. Similar to OpenStack cinder.

EC2 (Amazon Elastic Compute Cloud)

A public cloud run by Amazon. It provides similar functionality to OpenStack Compute.

Ephemeral Disk

Ephemeral disks offer machine local disk storage linked to the life cycle of a virtual machine instance. When a virtual machine is terminated, all data on the ephemeral disk is lost. Ephemeral disks are not included in any snapshots.


Occurs when a resource fails on a cluster node (or the node itself fails) and the affected resources are started on another node.


Describes the concept of preventing access to a shared resource by isolated or failing cluster members. Should a cluster node fail, it will be shut down or reset to prevent it from causing trouble. The resources running on the cluster node will be moved away to another node. This way, resources are locked out of a node whose status is uncertain.

Fixed IP Address

When an instance is launched, it is automatically assigned a fixed (private) IP address, which stays the same until the instance is explicitly terminated. Private IP addresses are used for communication between instances.


The compute, memory, and storage capacity of nova computing instances (in terms of virtual CPUs, RAM, etc.). Flavors can be thought of as templates for the amount of cloud resources that are assigned to an instance.

Floating IP Address

An IP address that a Compute project can associate with a virtual machine. A pool of floating IP addresses is available in OpenStack Compute, as configured by the cloud operator. After a floating IP address has been assigned to an instance, the instance can be reached from outside the cloud by this public IP address. Floating IP addresses can be dynamically disassociated and associated with other instances.


Code name for OpenStack Image.

Guest Operating System

An instance of an operating system installed on a virtual machine.


Code name for Orchestration.

High Availability Cluster

High Availability clusters seek to minimize two things: system downtime and data loss. System downtime occurs when a user-facing service is unavailable beyond a specified maximum amount of time. System downtime and data loss (data is accidentally destroyed) can occur not only in case of a single failure. There are also cases of cascading failures, where a single failure deteriorates into a series of consequential failures.


Code name for OpenStack Dashboard.


A physical computer.

Host Aggregate

An OpenStack method of grouping hosts via a common set of metadata. It enables you to tag groups of hosts with certain capabilities or characteristics. A characteristic could be related to physical location, allowing creation or further partitioning of availability zones. It could also be related to performance (for example, indicating the availability of SSD storage) or anything else that the cloud administrators deem appropriate. A host can be in more than one host aggregate.

Hybrid Cloud

One of several deployment models for a cloud infrastructure. A composition of both public and private clouds that remain unique entities, but are bound together by standardized technology for enabling data and application portability. Integrating SUSE Studio and SUSE Manager with SUSE OpenStack Cloud delivers a platform and tools with which to enable enterprise hybrid clouds.


A piece of computer software, firmware or hardware that creates and runs virtual machines. It arbitrates and controls access of the virtual machines to the underlying hardware.

IaaS (Infrastructure-as-a-Service)

A service model of cloud computing where processing, storage, networks, and other fundamental computing resources are rented over the Internet. It allows the customer to deploy and run arbitrary software, including operating systems and applications. The customer has control over operating systems, storage, and deployed applications but does not control the underlying cloud infrastructure. Housing and maintaining it is in the responsibility of the service provider.


A file that contains a complete Linux virtual machine.

In the SUSE OpenStack Cloud Crowbar context, images are virtual disk images that represent the contents and structure of a storage medium or device (such as a hard disk), in a single file. Images are used as a template from which a virtual machine can be started. For starting a virtual machine, SUSE OpenStack Cloud Crowbar always uses a copy of the image.

Images have both content and metadata; the latter are also called image properties.


A virtual machine that runs inside the cloud.

Instance Snapshot

A point-in-time copy of an instance. It preserves the disk state of a running instance and can be used to launch a new instance or to create a new image based upon the snapshot.


OpenStack Compute injects SSH keypair credentials that are injected into images when they are launched.


Code name for OpenStack Identity.


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

Linux Bridge

A software allowing multiple virtual machines to share a single physical NIC within OpenStack Compute. It behaves like a hub: You can connect multiple (physical or virtual) network interface devices to it. Any Ethernet frames that come in from one interface attached to the bridge is transmitted to all other devices.

Logical Volume (LV)

Acts as a virtual disk partition. After creating a Volume Group (VG), logical volumes can be created in that volume group. Logical volumes can be used as raw block devices, swap devices, or for creating a (mountable) file system like disk partitions.


The process of moving a virtual machine instance from one Compute Node to another. This process can only be executed by cloud administrators.


A technology used for a one-to-many communication within a network that can be used for cluster communication. Corosync supports both multicast and unicast.


In the OpenStack Networking API: An isolated L2 network segment (similar to a VLAN). It forms the basis for describing the L2 network topology in a given OpenStack Networking deployment.


Code name for OpenStack Networking.


A (physical) server that is managed by Crowbar.


Code name for OpenStack Compute.


Basic storage entity in OpenStack Object Storage, representing a file that your store there. When you upload data to OpenStack Object Storage, the data is neither compressed nor encrypted, it is stored as-is.

Open vBridge

A virtual networking device. It behaves like a virtual switch: network interface devices connect to its ports. The ports can be configured similar to a physical switch's port, including VLAN configurations.


A collection of open source software to build and manage public and private clouds. Its components are designed to work together to provide Infrastructure as a Service and massively scalable cloud computing software.

At the same time, OpenStack is also a community and a project.

OpenStack Block Storage

One of the core OpenStack components and services (code name: cinder). It provides persistent block level storage devices for use OpenStack compute instances. The block storage system manages the creation, attaching and detaching of the block devices to servers. Prior to the OpenStack Grizzly release, the service was part of nova-volume (block service).

OpenStack Compute

One of the core OpenStack components and services (code name: nova). It is a cloud computing fabric controller and as such, the main part of an IaaS system. It provides virtual machines on demand.

OpenStack Dashboard

One of the core OpenStack components or services (code name: horizon). It provides a modular Web interface for OpenStack services and allows end users and administrators to interact with each OpenStack service through the service's API.

OpenStack Identity

One of the core OpenStack components or services (code name: keystone). It provides authentication and authorization for all OpenStack services.

OpenStack Image

One of the core OpenStack components or services (code name: glance). It provides discovery, registration, and delivery services for virtual disk images.

OpenStack Networking

One of the core OpenStack components or services (code name: neutron). It provides network connectivity as a service between interface devices (for example, vNICs) managed by other OpenStack services (for example, Compute). Allows users to create their own networks and attach interfaces to them.

OpenStack Object Storage

One of the core OpenStack components or services (code name: swift). Allows to store and retrieve files while providing built-in redundancy and fail-over. Can be used for backing up and archiving data, streaming data to a user's Web browser, or developing new applications with data storage integration.

OpenStack Service

A collection of Linux services (or daemons) that work together to provide core functionality within the OpenStack project. This can be storing objects, providing virtual servers, or authentication and authorization. All services have code names, which are also used in configuration files, and command line programs.


A module (code name: heat) to orchestrate multiple composite cloud applications using file-based or Web-based templates. It contains both a user interface and an API and describes your cloud deployment in a declarative language. The module is an integrated project of OpenStack as of the Havana release.

PaaS (Platform-as-a-Service)

A service model of cloud computing where a computing platform and cloud-based application development tools are rented over the Internet. The customer controls software deployment and configuration settings, but not the underlying cloud infrastructure including network, servers, operating systems, or storage.


An open source cluster resource manager used in SUSE Linux Enterprise High Availability Extension.


In the OpenStack Networking API: An attachment port to an L2 OpenStack Networking network.

Private Cloud

One of several deployment models for a cloud infrastructure. The infrastructure is operated exclusively for a single organization and may exist on or off premises. The cloud is owned and managed by the organization itself, by a third party or a combination of both.

Private IP Address

See Fixed IP Address.


A concept in OpenStack Identity. Used to identify a group, an organization, or a project (or more generically, an individual customer environment in the cloud). Also called tenant. The term tenant is primarily used in the OpenStack command line tools.


Special configuration for a barclamp. It includes barclamp-specific settings, and a list of nodes to which the proposal should be applied.

Public Cloud

One of several deployment models for a cloud infrastructure. The cloud infrastructure is designed for use by the general public and exists on the premises of the cloud provider. Services like applications, storage, and other resources are made available to the general public for free or are offered on a pay-per-use model. The infrastructure is owned and managed by a business, academic or government organization, or some combination of these.

Public IP Address

See Floating IP Address.

qcow (QEMU Copy on Write)

A disk image format supported by the QEMU virtual machine manager. A qcow2 image helps to optimize disk space. It consumes disk space only when contents are written on it and grows as data is added.

qcow2 is a more recent version of the qcow format where a read-only base image is used, and all writes are stored to the qcow2 image.


In a cluster, a Cluster Partition is defined to have quorum (is quorate) if it has the majority of nodes (or votes). Quorum distinguishes exactly one partition. It is part of the algorithm to prevent several disconnected partitions or nodes from proceeding and causing data and service corruption (Split Brain). Quorum is a prerequisite for Fencing, which then ensures that quorum is indeed unique.


Restriction of resources to prevent overconsumption within a cloud. In OpenStack, quotas are defined per project and contain multiple parameters, such as amount of RAM, number of instances, or number of floating IP addresses.

RC File (openrc.sh)

Environment file needed for the OpenStack command line tools. The RC file is project-specific and contains the credentials used by OpenStack Compute, Image, and Identity services.


A group of Chef scripts and templates. Recipes are used by Chef to deploy a unit of functionality.


An OpenStack method of aggregating clouds. Regions are a robust way to share some infrastructure between OpenStack compute installations, while allowing for a high degree of failure tolerance. Regions have a separate API endpoint per installation.


In a High Availability context: Any type of service or application that is known to the cluster resource manager. Examples include an IP address, a file system, or a database.

Resource Agent (RA)

A script acting as a proxy to manage a resource in a High Availability cluster. For example, it can start, stop or monitor a resource.


In the Crowbar/Chef context: an instance of a Proposal that is active on a node.

In the OpenStack Identity context: concept of controlling the actions or set of operations that a user is allowed to perform. A role includes a set of rights and privileges. A user assuming that role inherits those rights and privileges.

S3 (Amazon Simple Storage Service)

An object storage by Amazon that can be used to store and retrieve data on the Web. Similar in function to OpenStack Object Storage. It can act as a back-end store for glance images.

SaaS (Software-as-a-Service)

A service model of cloud computing where applications are hosted by a service provider and made available to customers remotely as a Web-based service.

SBD (STONITH Block Device)

In an environment where all nodes of a High Availability cluster have access to shared storage, a small partition is used for disk-based fencing.

Security Group

Concept in OpenStack Networking. A security group is a container for security group rules. Security group rules allow to specify the type of traffic and direction (ingress/egress) that is allowed to pass through a port.

Sequence number (seqno)

A term from a MariaDB Galera Cluster which is used for replication. It's a 64-bit signed integer that the node uses to denote the position of a given transaction in the sequence.

Single Point of Failure (SPOF)

An individual piece of equipment or software which will cause system downtime or data loss if it fails. To eliminate single points of failure, High Availability systems seek to provide redundancy for crucial pieces of equipment or software.


When you first boot a node in SUSE OpenStack Cloud Crowbar via PXE, it is booted with the SLEShammer image. This performs the initial hardware discovery, and registers the node with Crowbar. After you allocate the node, it is rebooted with a regular SLES installation image.


See Volume Snapshot or Instance Snapshot.

Split Brain

Also known as a partitioned cluster scenario. Either through a software or hardware failure, the cluster nodes are divided into two or more groups that do not know of each other. STONITH prevents a split brain situation from badly affecting the entire cluster.

Stateful Service

A service where subsequent requests to the service depend on the results of the first request.

Stateless Service

A service that provides a response after your request, and then requires no further attention.


The acronym for Shoot the other node in the head. It refers to the fencing mechanism that shuts down a misbehaving node to prevent it from causing trouble in a cluster.

Storage Node

Node within a SUSE OpenStack Cloud. Acts as the controller for cloud-based storage. A cloud can contain multiple Storage Nodes.


In the OpenStack Networking API: A block of IP addresses and other network configuration (for example, a default gateway, DNS servers) that can be associated with an OpenStack Networking network. Each subnet represents an IPv4 or IPv6 address block. Multiple subnets can be associated with a network, if necessary.

SUSE Linux Enterprise High Availability Extension

An integrated suite of open source clustering technologies that enables you to implement highly available physical and virtual Linux clusters.

SUSE OpenStack Cloud Administrator

User role in SUSE OpenStack Cloud Crowbar. Manages projects, users, images, flavors, and quotas within SUSE OpenStack Cloud Crowbar.

SUSE OpenStack Cloud Dashboard

The SUSE® OpenStack Cloud Crowbar Dashboard is a Web interface that enables cloud administrators and users to manage various OpenStack services. It is based on OpenStack Dashboard (also known under its codename horizon).

SUSE OpenStack Cloud Operator

User role in SUSE OpenStack Cloud Crowbar. Installs and deploys SUSE OpenStack Cloud Crowbar.

SUSE OpenStack Cloud User

User role in SUSE OpenStack Cloud Crowbar. End user who launches and manages instances, can create snapshots, and use volumes for persistent storage within SUSE OpenStack Cloud Crowbar.


Code name for OpenStack Object Storage.

TAP Device

A virtual networking device. A TAP device, such as vnet0 is how hypervisors such as KVM and Xen implement a virtual network interface card (vNIC). An Ethernet frame sent to a TAP device is received by the guest operating system. The tap option connects the network stack of the guest operating system to a TAP network device on the host.


A module (code name: ceilometer) for metering OpenStack-based clouds. The project aims to provide a unique point of contact across all OpenStack core components for acquiring metrics. The metrics can then be consumed by other components such as customer billing. The module is an integrated project of OpenStack as of the Havana release.


See Project.


A technology for sending messages to a single network destination. Corosync supports both multicast and unicast. In Corosync, unicast is implemented as UDP-unicast (UDPU).


In the OpenStack context, a digital representation of a person, system, or service who uses OpenStack cloud services. Users can be directly assigned to a particular project and behave as if they are contained in that project.

Veth Pair

A virtual networking device. The acronym veth stands for virtual Ethernet interface. A veth is a pair of virtual network interfaces correctly directly together. An Ethernet frame sent to one end of a veth pair is received by the other end of a veth pair. OpenStack Networking uses veth pairs as virtual patch cables to make connections between virtual bridges.


A physical method for network virtualization. VLANs allow to create virtual networks across a distributed network. Disparate hosts (on independent networks) appear as if they were part of the same broadcast domain.

VM (Virtual Machine)

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


Virtual network interface card.


Detachable block storage device. Unlike a SAN, it can only be attached to one instance at a time.

Volume Group (VG)

A virtual disk consisting of aggregated physical volumes. Volume groups can be logically partitioned into logical volumes.

Volume Snapshot

A point-in-time copy of an OpenStack storage volume. Used to back up volumes.

vSwitch (Virtual Switch)

A software that runs on a host or node and provides the features and functions of a hardware-based network switch.


A logical grouping of Compute services and virtual machine hosts.