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@ -8,37 +8,37 @@ Qubes User's FAQ
================
1. [General Questions](#GeneralQuestions)
1. [Isn’t Qubes just another Linux distribution after all?](#IsntQubesjustanotherLinuxdistributionafterall)
1. [Is Qubes just another Linux distribution?](#IsQubesjustanotherLinuxdistribution)
2. [How is Qubes different from other security solutions?](#HowisQubesdifferentfromothersecuritysolutions)
3. [What is the main concept behind Qubes?](#WhatisthemainconceptbehindQubes)
4. [What about other approaches to security?](#Whataboutotherapproachestosecurity)
5. [But what about safe languages and formally verified microkernels?](#Butwhataboutsafelanguagesandformallyverifiedmicrokernels)
6. [Why Qubes uses virtualization?](#WhyQubesusesvirtualization)
5. [What about safe languages and formally verified microkernels?](#Whataboutsafelanguagesandformallyverifiedmicrokernels)
6. [Why does Qubes use virtualization?](#WhydoesQubesusevirtualization)
7. [Does Qubes run every app in a separate VM?](#DoesQubesruneveryappinaseparateVM)
8. [Why Qubes uses Xen, and not e.g. KVM or some other hypervisor?](#WhyQubesusesXenandnote.g.KVMorsomeotherhypervisor)
9. [What is so special about Qubes GUI virtualization?](#WhatissospecialaboutQubesGUIvirtualization)
10. [Can I watch movies in AppVMs, e.g. YouTube? movies?](#CanIwatchmoviesinAppVMse.g.YouTubemovies)
11. [How about running applications like games that required 3D support?](#Howaboutrunningapplicationslikegamesthatrequired3Dsupport)
8. [Why does Qubes use Xen instead of KVM or some other hypervisor?](#WhydoesQubesuseXeninsteadofKVMorsomeotherhypervisor)
9. [What's so special about Qubes' GUI virtualization?](#WhatssospecialaboutQubesGUIvirtualization)
10. [Can I watch YouTube? videos in AppVMs?](#CanIwatchYouTubevideosinAppVMs)
11. [Can I run applications, like games, which require 3D support?](#CanIrunapplicationslikegameswhichrequire3Dsupport)
12. [Is Qubes a multi-user system?](#IsQubesamulti-usersystem)
2. [Installation/hardware compatibility](#Installationhardwarecompatibility)
1. [How much disk space do I need for each AppVM?](#HowmuchdiskspacedoIneedforeachAppVM)
2. [Installation & Hardware Compatibility](#InstallationHardwareCompatibility)
1. [How much disk space does each AppVM require?](#HowmuchdiskspacedoeseachAppVMrequire)
2. [How much memory is recommended for Qubes?](#HowmuchmemoryisrecommendedforQubes)
3. [Can I install Qubes on a system without VT-x?](#CanIinstallQubesonasystemwithoutVT-x)
4. [Can I install Qubes on a system without VT-d?](#CanIinstallQubesonasystemwithoutVT-d)
5. [Can I use AMD-v instead of VT-x?](#CanIuseAMD-vinsteadofVT-x)
6. [Can I install Qubes in a Virtual Machine, e.g. on VMWare?](#CanIinstallQubesinaVirtualMachinee.g.onVMWare)
6. [Can I install Qubes in a virtual machine (e.g., on VMWare)?](#CanIinstallQubesinavirtualmachinee.g.onVMWare)
General Questions
-----------------
### Isn’t Qubes just another Linux distribution after all?
### Is Qubes just another Linux distribution?
Well, if you really want to call it a distribution, then we’re more of a “Xen distribution”, rather then a Linux one. But Qubes is much more than just Xen packaging -- it has its own VM management infrastructure, with support for template VMs, centralized VM updating, etc, and also its very unique GUI virtualization infrastructure.
If you really want to call it a distribution, then it's more of a "Xen distribution" than a Linux one. But Qubes is much more than just Xen packaging. It has its own VM management infrastructure, with support for template VMs, centralized VM updating, etc. It also has a very unique GUI virtualization infrastructure.
### How is Qubes different from other security solutions?
Please see [​this article](http://theinvisiblethings.blogspot.com/2012/09/how-is-qubes-os-different-from.html) for a more thorough discussion discussion.
Please see [​this article](http://theinvisiblethings.blogspot.com/2012/09/how-is-qubes-os-different-from.html) for a thorough discussion.
### What is the main concept behind Qubes?
@ -46,74 +46,70 @@ To build security on the “Security by Isolation” principle.
### What about other approaches to security?
The other two popular [​approaches](http://theinvisiblethings.blogspot.com/2008/09/three-approaches-to-computer-security.html) are: “Security by Correctness”, and “Security by Obscurity”. We don’t believe any of those two can bring reasonable security today and in the foreseeable future.
The other two popular [​approaches](http://theinvisiblethings.blogspot.com/2008/09/three-approaches-to-computer-security.html) are “Security by Correctness” and “Security by Obscurity.” We don't believe either of these approaches are capable of providing reasonable security today, nor do we believe that they will be capable of doing so in the foreseeable future.
### But what about safe languages and formally verified microkernels?
### What about safe languages and formally verified microkernels?
In short: these are non-realistic solutions today. We discuss this more in-depth in our [​Architecture Specification document](http://files.qubes-os.org/files/doc/arch-spec-0.3.pdf).
In short: these are non-realistic solutions today. We discuss this in further depth in our [​Architecture Specification document](http://files.qubes-os.org/files/doc/arch-spec-0.3.pdf).
### Why Qubes uses virtualization?
### Why does Qubes use virtualization?
We believe that today this is the only practically viable approach to implement strong isolation, and, at the same time, provide compatibility with existing applications and drivers.
We believe that this is currently the only practically viable approach to implementing strong isolation while simultaneously providing compatibility with existing applications and drivers.
### Does Qubes run every app in a separate VM?
No! This would not make much sense. Qubes uses lightweight VMs to create security domains, such as e.g. ‘work’, ‘personal’, ‘banking’, etc. Typical user would likely need around 5 domains. Very paranoid users, who are high-profile targets. might use around a dozen or more domains.
No! This would not make much sense. Qubes uses lightweight VMs to create security domains (e.g., "work," "personal," and "banking,"). A typical user would likely need around five domains. Very paranoid users, or those who are high-profile targets, might use a dozen or more domains.
### Why Qubes uses Xen, and not e.g. KVM or some other hypervisor?
### Why does Qubes use Xen instead of KVM or some other hypervisor?
In short: we believe the Xen architecture allows to create more secure systems, i.e. with much smaller TCB, which translates to smaller attack surface. We discuss this much more in-depth in our [​Architecture Specification document](http://files.qubes-os.org/files/doc/arch-spec-0.3.pdf).
In short: we believe the Xen architecture allows for the creation of more secure systems (i.e. with a much smaller TCB, which translates to a smaller attack surface). We discuss this in much greater depth in our [​Architecture Specification document](http://files.qubes-os.org/files/doc/arch-spec-0.3.pdf).
### What is so special about Qubes GUI virtualization?
### What's so special about Qubes' GUI virtualization?
We have designed the GUI virtualization subsystem with two primary goals: security and performance. Our GUI infrastructure introduces only about 2,500 lines of C code (LOC) into the privileged domain (Dom0), which is very little, and thus leaves not much space for bugs and potential attacks. At the same time, due to smart use of Xen shared memory our GUI implementation is very efficient, so most virtualized applications really feel like if they were executed natively.
We have designed the GUI virtualization subsystem with two primary goals: security and performance. Our GUI infrastructure introduces only about 2,500 lines of C code (LOC) into the privileged domain (Dom0), which is very little, and thus leaves little space for bugs and potential attacks. At the same time, due to the smart use of Xen shared memory, our GUI implementation is very efficient, so most virtualized applications really feel as if they were executed natively.
### Can I watch movies in AppVMs, e.g. [YouTube?](/wiki/YouTube) movies?
### Can I watch [YouTube?](/wiki/YouTube) videos in AppVMs?
Absolutely.
### How about running applications like games that required 3D support?
### Can I run applications, like games, which require 3D support?
Those won’t fly. We do not provide OpenGL virtualization for AppVMs. This is mostly a security decision, as implementing such feature would most likely introduce lots of complexity to the GUI virtualization infrastructure. However, Qubes allows for use of accelerated graphics (OpenGL) in Dom0’s Window Manager, so all the fancy desktop effects should still work under Qubes.
Those won’t fly. We do not provide OpenGL virtualization for AppVMs. This is mostly a security decision, as implementing such a feature would most likely introduce a great deal of complexity into the GUI virtualization infrastructure. However, Qubes does allow for the use of accelerated graphics (OpenGL) in Dom0’s Window Manager, so all the fancy desktop effects should still work.
You can read more discussions about potential GPU passthorugh on [Xen/Qubes?](/wiki/Xen/Qubes) and other disucssions on the topic on the following threads from qubes-devel:
For further discussion about the potential for GPU passthorugh on [Xen/Qubes?](/wiki/Xen/Qubes), please see the following threads:
- [​GPU passing to HVM](https://groups.google.com/group/qubes-devel/browse_frm/thread/31f1f2da39978573?scoring=d&q=GPU&)
- [​Clarifications on GPU security](https://groups.google.com/group/qubes-devel/browse_frm/thread/31e2d8a47c8b4474?scoring=d&q=GPU&)
### Is Qubes a multi-user system?
No, Qubes does not pretend to be a multi-user system. Qubes assumes that the user that controls Dom0, controls the whole system. It will be very difficult to **securely** implement multi-user support -- see this message:
No. Qubes does not pretend to be a multi-user system. Qubes assumes that the user who controls Dom0 controls the whole system. It would be very difficult to **securely** implement multi-user support. See [​here](https://groups.google.com/group/qubes-devel/msg/899f6f3efc4d9a06) for details.]
[​https://groups.google.com/group/qubes-devel/msg/899f6f3efc4d9a06](https://groups.google.com/group/qubes-devel/msg/899f6f3efc4d9a06)
Installation & Hardware Compatibility
-------------------------------------
Installation/hardware compatibility
-----------------------------------
(See also: [System Requirements](/wiki/SystemRequirements) and [Hardware Compatibility List](/wiki/HCL).)
### How much disk space do I need for each AppVM?
### How much disk space does each AppVM require?
Every AppVM is created from a so called TemplateVM and they share the root filesystem with the template (in a read-only manner). This means each AppVM needs only disk space for its own private data. This also means that it is possible to update the software for all the AppVMs by just running the update process in the TemplateVM once (one needs to stop all the AppVMs for this, of course).
Each AppVM is created from a TemplateVM and shares the root filesystem with this TemplateVM (in a read-only manner). This means that each AppVM needs only as much disk space as is necessary to store its own private data. This also means that it is possible to update the software for several AppVMs simultaneously by running a single update process in the TemplateVM upon which those AppVMs are based. (These AppVMs will then have to be restarted in order for the update to take effect in them.)
### How much memory is recommended for Qubes?
4 GB at least. Sure, you can try it on a system with 2GB, but don't expect to be able to run more than 3 AppVMs at the same time...
At least 4 GB. It is possible to install Qubes on a system with 2 GB of RAM, but the system would probably not be able to run more than three AppVMs at a time.
### Can I install Qubes on a system without VT-x?
Yes. Xen doesn't use VT-x (nor AMD-v) for PV guests virtualization (it uses ring0/3 separation instead). But, of course, without VT-x, you will also not have VT-d -- see the next question.
Also, without VT-x you won't be able to use fully virtualized VMs (e.g. Windows-based AppVMs) that are to be introduced in Qubes 2.
Yes. Xen doesn't use VT-x (or AMD-v) for PV guest virtualization. (It uses ring0/3 separation instead.) However, without VT-x, you won't be able to use fully virtualized VMs (e.g., Windows-based AppVMs), which were introduced in Qubes 2. In addition, if your system lacks VT-x, then it also lacks VT-d. (See next question.)
### Can I install Qubes on a system without VT-d?
Yes you can. You can even run a netvm but, of course, you will not benefit from DMA protection for driver domains. So, on a system without VT-d, everything should work the same, but there is no real security benefit of having a separate netvm, as the attacker can always use a simple DMA attack to go from netvm to Dom0.
**But still, all the other Qubes security mechanisms, such as AppVM separation, work as usual, and you still end up with a significantly secure OS, much more secure then Windows, Mac, or Linux, even if you don't have VT-d'''**
Yes. You can even run a NetVM, but you will not benefit from DMA protection for driver domains. On a system without VT-d, everything should work in the same way, except there will be no real security benefit to having a separate NetVM, as an attacker could always use a simple DMA attack to go from the NetVM to Dom0. **Nonetheless, all of Qubes' other security mechanisms, such as AppVM separation, work without VT-d. Therefore, a system running Qubes will still be significantly more secure than one running Windows, Mac, or Linux, even if it lacks VT-d.**
### Can I use AMD-v instead of VT-x?
See [​this message](http://groups.google.com/group/qubes-devel/msg/6412170cfbcb4cc5).
### Can I install Qubes in a Virtual Machine, e.g. on VMWare?
### Can I install Qubes in a virtual machine (e.g., on VMWare)?
Most likely no. You should install it on bare-metal. Hey, it uses its own bare-metal hypervisor, after all...
Some users have been able to do this, but it is neither recommended nor supported. Qubes should be installed bare-metal. (After all, it uses its own bare-metal hypervisor!)