qubes-doc/user/reference/glossary.md

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lang: en
layout: doc
permalink: /doc/glossary/
redirect_from:
- /en/doc/glossary/
- /doc/Glossary/
- /wiki/Glossary/
ref: 140
title: Glossary
---

## app qube

Any [qube](#qube) that depends on a [template](#template) for its root
filesystem.

* Historical note: This term originally meant "a qube intended for running user
  software applications" (hence the name "app").

* Historical note: This is the preferred term replacing the deprecated term
  "TemplateBasedVM."

## disposable

See [How to Use Dispoables](/doc/how-to-use-disposables/). A temporary [app
qube](#app-qube) based on a [disposable template](#disposable-template) that
can quickly be created, used, and destroyed.

## disposable template

A type of [app qube](#app-qube) on which [disposables](#disposable) are based.
(Not to be confused with the concept of a [template](#template) that is itself
disposable, which does not exist in Qubes OS.)

Disposable templates are not [templates](#template), since (being app qubes)
they do not have root filesystems of their own to provide to other qubes.
Rather, disposable templates are complementary to templates insofar as
disposable templates provide their own user filesystems to the disposables
based on them.

## dom0

[Domain](#domain) Zero. Also known as the **host** domain, dom0 is the initial
qube started by the Xen hypervisor on boot. Dom0 runs the Xen management
toolstack and has special privileges relative to other domains, such as direct
access to most hardware.

* The term "dom0" is not a proper noun and should not be capitalized unless
  it's the first word in a sentence.

* The use of [domain](#domain) as a synonym for [VM](#vm) is specific to Xen.
  Qubes diverges from this practice. See: [domain](#domain).

## domain

_This term is deprecated in the context of Qubes OS._

In Xen, a synonym for [VM](#vm). See ["domain" on the Xen
Wiki](https://wiki.xenproject.org/wiki/Domain).

## domU

Unprivileged [domain](#domain). Also known as **guest** domains, domUs are the
counterparts to dom0. In Xen, all VMs except dom0 are domUs. By default, most
domUs lack direct hardware access.

* The term "domU" is not a proper noun and should not be capitalized unless it
  is the first word in a sentence.

* The use of [domain](#domain) as a synonym for [VM](#vm) is specific to Xen.
  Qubes diverges from this practice. See: [domain](#domain).

## HVM

[Hardware-assisted Virtual Machine](/doc/standalones-and-HVM/). Any fully
virtualized, or hardware-assisted, [VM](#vm) utilizing the virtualization
extensions of the host CPU. Although HVMs are typically slower than
paravirtualized qubes due to the required emulation, HVMs allow the user to
create domains based on any operating system.

## qube

A secure compartment in Qubes OS. Currently, qubes are implemented as Xen
[VMs](#vm), but Qubes OS is independent of its underlying compartmentalization
technology. VMs could be replaced with a different technology, and qubes would
still be called "qubes."

* **Important:** The term "qube" should be lowercase unless it is the first
  word in a sentence. Note that starting a sentence with the plural of "qube"
  (i.e., "Qubes...") can be ambiguous, since it may not be clear whether the
  referent is a collection of qubes or [Qubes OS](#qubes-os).

* Example usage: "In Qubes OS, you do your banking in your 'banking' qube and
  your web surfing in your 'untrusted' qube. That way, if your 'untrusted' qube
  is compromised, your banking activities will remain secure."

* Historical note: The term "qube" was originally invented as an alternative to
  "VM" intended to make it easier for less technical users to understand Qubes
  OS and learn how to use it.

## Qubes OS

A security-oriented operating system (OS). The main principle of Qubes OS is
security by compartmentalization (or isolation), in which activities are
compartmentalized (or isolated) in separate [qubes](#qube).

* **Important:** The official name is "Qubes OS" (note the capitalization and
  the space between "Qubes" and "OS"). However, in casual conversation this is
  often shortened to "Qubes." Only in technical contexts where spaces are not
  permitted (e.g., usernames) may the space be omitted, as in `@QubesOS`.

## Qubes Windows Tools

[Qubes Windows Tools (QWT)](/doc/windows-tools/) are a set of programs and
drivers that provide integration of Windows qubes with the rest of the Qubes OS
system. Also see [Windows](/doc/windows/).

## service qube

A [qube](#qube) the primary purpose of which is to provide a service or
services to other qubes. `sys-net` and `sys-firewall` are examples of service
qubes.

## standalone

See [Standalones and HVMs](/doc/standalones-and-hvm/). A type of [qube](#qube)
that does not depend on any other qube for its root filesystem. The opposite of
an app qube. A standalone is created by cloning a template. Unlike templates,
however, standalones do not supply their root filesystems to other qubes.

## template

See [Templates](/doc/templates/). Any [qube](#qube) that supplies its root
filesystem to another qube. Templates are intended for installing and updating
software applications, but not for running them.

* Since every template supplies its *own* root filesystem to at least one other
  qube, no template can be based on another template. In other words, no
  template is an [app qube](#app-qube).

* Since every template supplies its *root* filesystem to at least one other
  qube, no [disposable template](#disposable-template) is a template.

## VM

An abbreviation for "virtual machine." A software implementation of a machine
(for example, a computer) that executes programs like a physical machine.