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* Add definition for "VM" * Re-define "domain" (QubesOS/qubes-issues#1015) * Add cross-reference links throughout the page * Many other small updates and fixes
176 lines
6.9 KiB
Markdown
176 lines
6.9 KiB
Markdown
---
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layout: doc
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title: Glossary
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permalink: /doc/glossary/
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redirect_from:
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- /en/doc/glossary/
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- /doc/Glossary/
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- /wiki/Glossary/
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---
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Glossary of Qubes Terminology
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=============================
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Qubes OS
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--------
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A security-oriented operating system (OS). The main principle of Qubes OS is
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security by compartmentalization (or isolation), in which activities are
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compartmentalized (or isolated) in separate **qubes**.
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* The official name is `Qubes OS` (note the capitalization and spacing).
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However, in casual conversation this is often shortened to `Qubes`, and in
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technical contexts where spaces are not permitted, (e.g., usernames), the
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space may be omitted, as in `QubesOS`.
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VM
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--
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An abbreviation for "virtual machine." A software implementation of a machine
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(for example, a computer) which executes programs like a physical machine.
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Qube
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----
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A user-friendly term for a [VM](#vm) in Qubes OS.
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* Example: "In Qubes OS, you do your banking in your 'banking' qube and your
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web surfing in your 'untrusted' qube. That way, if your 'untrusted' qube is
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compromised, your banking activities will remain secure."
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* "Qube" is an informal term intended to make it easier for less technical
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users to understand Qubes OS and learn how to use it. In technical
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discussions, the other, more precise terms defined on this page are to be
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preferred.
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* The term "qube" should be lowercase unless it is the first word in a
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sentence. Note that starting a sentence with the plural of "qube" (i.e.,
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"Qubes...") can be ambiguous, since it may not be clear whether the referent
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is a collection of qubes or [Qubes OS](#qubes-os).
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Domain
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------
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An area or set of activities in one's digital life that has certain security
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requirements and therefore involves the use of certain [qubes](#qube). For
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example, suppose your "email" domain encompasses the activity of sending
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PGP-encrypted email. This domain may include your email qube and your [Split
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GPG](/doc/split-gpg) qube. Note that domains and qubes are not the same thing.
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In this example, your "email" domain includes the use of two qubes. Furthermore,
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a qube can fall under multiple domains simultaneously. For example, your Split
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GPG qube may also be part of your "software development" domain if you PGP-sign
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your Git commits.
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Dom0
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----
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Domain Zero. Also known as the **host** domain, dom0 is the initial VM
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started by the Xen hypervisor on boot. Dom0 runs the Xen management toolstack
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and has special privileges relative to other domains, such as direct access to
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most hardware. (Note that the use of "domain" for a synonym for "VM" is specific
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to Xen. Qubes diverges from this practice. See: [domain](#domain).)
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DomU
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----
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Unprivileged Domain. Also known as **guest** domains, domUs are the counterparts
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to dom0. All VMs except dom0 are domUs. By default, most domUs lack direct
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hardware access. (Note that the use of "domain" for a synonym for "VM" is
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specific to Xen. Qubes diverges from this practice. See: [domain](#domain).)
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TemplateVM
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----------
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Template Virtual Machine. Any [VM](#vm) which supplies its root filesystem to
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another VM. TemplateVMs are intended for installing and updating software
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applications, but not for running them.
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* Colloquially, TemplateVMs are often referred to as "templates."
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TemplateBasedVM
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---------------
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Any [VM](#vm) which depends on a TemplateVM for its root filesystem.
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Standalone(VM)
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--------------
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Standalone (Virtual Machine). In general terms, a [VM](#vm) is described as
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**standalone** if and only if it does not depend on any other VM for its root
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filesystem. (In other words, a VM is standalone if and only if it is not a
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TemplateBasedVM.) More specifically, a **StandaloneVM** is a type of VM in Qubes
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which is created by cloning a TemplateVM. Unlike TemplateVMs, however,
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StandaloneVMs do not supply their root filesystems to other VMs. (Therefore,
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while a TemplateVM is a type of standalone VM, it is not a StandaloneVM.)
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AppVM
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-----
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Application Virtual Machine. A [VM](#vm) which is intended for running software
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applications. Typically a TemplateBasedVM, but may be a StandaloneVM. Never a
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TemplateVM.
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NetVM
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-----
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Network Virtual Machine. A type of [VM](#vm) which connects directly to a
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network and provides access to that network to other VMs which connect to the
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NetVM. A NetVM called `sys-net` is created by default in most Qubes
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installations.
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Alternatively, "NetVM" may refer to whichever VM is directly connected to a VM
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for networking purposes. For example, if `untrusted` is directly connected to
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`sys-firewall` for network access, then it is accurate to say, "`sys-firewall`
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is `untrusted`'s NetVM," even though `sys-firewall` is a ProxyVM.
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ProxyVM
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-------
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Proxy Virtual Machine. A type of [VM](#vm) which proxies network access for
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other VMs. Typically, a ProxyVM sits between a NetVM and another VM (such as an
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AppVM or a TemplateVM) which requires network access.
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FirewallVM
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----------
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Firewall Virtual Machine. A type of [ProxyVM](#proxyvm) which is used to enforce
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network-level policies (a.k.a. "firewall rules"). A FirewallVM called
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`sys-firewall` is created by default in most Qubes installations.
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DispVM
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------
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Disposable Virtual Machine. A temporary [AppVM](#appvm) which can quickly be
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created, used, and destroyed.
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DVM
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---
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An abbreviation of [DispVM](#dispvm), typically used to refer to the TemplateVM
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on which DispVMs are based. By default, a VM named `fedora-XX-dvm` is created on
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most Qubes installations (where `XX` is the current Fedora version).
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PV
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--
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Paravirtualization. An efficient and lightweight virtualization technique
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originally introduced by the Xen Project and later adopted by other
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virtualization platforms. Unlike HVMs, paravirtualized [VMs](#vm) do not require
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virtualization extensions from the host CPU. However, paravirtualized VMs
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require a PV-enabled kernel and PV drivers, so the guests are aware of the
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hypervisor and can run efficiently without emulation or virtual emulated
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hardware.
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HVM
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---
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Hardware Virtual Machine. Any fully virtualized, or hardware-assisted, [VM](#vm)
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utilizing the virtualization extensions of the host CPU. Although HVMs are
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typically slower than paravirtualized VMs due to the required emulation, HVMs
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allow the user to create domains based on any operating system.
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StandaloneHVM
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-------------
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Any [HVM](#hvm) which is standalone (i.e., does not depend on any other VM for
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its root filesystem). In Qubes, StandaloneHVMs are referred to simply as
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**HVMs**.
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TemplateHVM
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-----------
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Any [HVM](#hvm) which functions as a [TemplateVM](#templatevm) by supplying its
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root filesystem to other VMs. In Qubes, TemplateHVMs are referred to as **HVM
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templates**.
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PVH
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---
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[PV](#pv) on [HVM](#hvm). To boost performance, fully virtualized HVM guests can
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use special paravirtual device drivers (PVHVM or PV-on-HVM drivers). These
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drivers are optimized PV drivers for HVM environments and bypass the emulation
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for disk and network I/O, thus providing PV-like (or better) performance on HVM
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systems. This allows for optimal performance on guest operating systems such as
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Windows.
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