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183 lines
9.6 KiB
Markdown
183 lines
9.6 KiB
Markdown
---
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layout: doc
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title: DisposableVMs
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permalink: /doc/disposablevm/
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redirect_from:
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- /doc/dispvm/
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- /en/doc/dispvm/
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- /doc/DisposableVms/
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- /wiki/DisposableVMs/
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---
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# DisposableVMs #
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A DisposableVM (previously known as a "DispVM") is a lightweight VM that can be created quickly and will disappear when closed.
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DisposableVMs are usually created in order to host a single application, like a viewer, editor, or web browser.
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From inside an AppVM, choosing the `Open in DisposableVM` option on a file will launch a DisposableVM for just that file.
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Changes made to a file opened in a DisposableVM are passed back to the originating VM.
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This means that you can safely work with untrusted files without risk of compromising your other VMs.
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DisposableVMs can be launched either directly from dom0's Start Menu or terminal window, or from within AppVMs.
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While running, DisposableVMs will appear in Qubes VM Manager with the name `disp####`.
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See [this article](https://blog.invisiblethings.org/2010/06/01/disposable-vms.html) for more on why one would want to use a DisposableVM.
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## Security ##
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If a [DisposableVM Template] becomes compromised, then any DisposableVM based on that DisposableVM Template could be compromised.
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In particular, the *default* DisposableVM Template is important because it is used by the "Open in DisposableVM" feature.
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This means that it will have access to everything that you open with this feature.
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For this reason, it is strongly recommended that you base the default DisposableVM Template on a trusted TemplateVM.
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### DisposableVMs and Local Forensics ###
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At this time, DisposableVMs should not be relied upon to circumvent local forensics, as they do not run entirely in RAM.
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For details, see [this thread](https://groups.google.com/d/topic/qubes-devel/QwL5PjqPs-4/discussion).
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When it is essential to avoid leaving any trace, consider using [Tails](https://tails.boum.org/).
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## DisposableVMs and Networking ##
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Similarly to how AppVMs are based on their underlying [TemplateVM](https://www.qubes-os.org/doc/glossary/#templatevm), DisposableVMs are based on their underlying [DisposableVM Template](https://www.qubes-os.org/doc/glossary/#disposablevm-template).
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R4.0 introduces the concept of multiple DisposableVM Templates, whereas R3.2 was limited to only one.
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On a fresh installation of Qubes, the default DisposableVM Template is called `fedora-XX-dvm` (where `XX` is the Fedora version of the default TemplateVM).
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If you have included the Whonix option in your install, there will also be a `whonix-ws-dvm` DisposableVM Template available for your use.
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You can set any AppVM to have the ability to act as a DisposableVM Template with:
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qvm-prefs <vmname> template_for_dispvms True
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The default system wide DisposableVM Template can be changed with `qubes-prefs default_dispvm`.
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By combining the two, choosing `Open in DisposableVM` from inside an AppVM will open the document in a DisposableVM based on the default DisposableVM Template you specified.
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You can change this behaviour for individual VMs: in the Application Menu, open Qube Settings for the VM in question and go to the "Advanced" tab.
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Here you can edit the "Default DisposableVM" setting to specify which DisposableVM Template will be used to launch DisposableVMs from that VM.
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This can also be changed from the command line with:
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qvm-prefs <vmname> default_dispvm <dvmtemplatename>
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For example, `anon-whonix` has been set to use `whonix-ws-dvm` as its `default_dispvm`, instead of the system default.
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You can even set an AppVM that has also been configured as a DisposableVM Template to use itself, so DisposableVMs launched from within the AppVM/DisposableVM Template would inherit the same settings.
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NetVM and firewall rules for DisposableVM Templates can be set as they can for a normal VM.
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By default a DisposableVM will inherit the NetVM and firewall settings of the DisposableVM Template on which it is based.
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This is a change in behaviour from R3.2, where DisposableVMs would inherit the settings of the AppVM from which they were launched.
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Therefore, launching a DisposableVM from an AppVM will result in it using the network/firewall settings of the DisposableVM Template on which it is based.
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For example, if an AppVM uses sys-net as its NetVM, but the default system DisposableVM uses sys-whonix, any DisposableVM launched from this AppVM will have sys-whonix as its NetVM.
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**Warning:** The opposite is also true.
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This means if you have changed anon-whonix's `default_dispvm` to use the system default, and the system default DisposableVM uses sys-net, launching a DisposableVM from inside anon-whonix will result in the DisposableVM using sys-net.
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A DisposableVM launched from the Start Menu inherits the NetVM and firewall settings of the DisposableVM Template on which it is based.
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Note that changing the "NetVM" setting for the system default DisposableVM Template *does* affect the NetVM of DisposableVMs launched from the Start Menu.
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Different DisposableVM Templates with individual NetVM settings can be added to the Start Menu.
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**Important Notes:**
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Some DisposableVM Templates will automatically create a menu item to launch a DVM, if you do not see an entry and want to add one please use the command:
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qvm-features deb-dvm appmenus-dispvm 1
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To launch a DVM from the command line, in dom0 please type the following:
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qvm-run --dispvm=NameOfDVM --service qubes.StartApp+NameOfApp
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## Opening a file in a DisposableVM via GUI ##
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In an AppVM's file manager, right click on the file you wish to open in a DisposableVM, then choose "Open in DisposableVM".
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Wait a few seconds and the default application for this file type should appear displaying the file content.
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This app is running in its own dedicated VM -- a DisposableVM created for the purpose of viewing or editing this very file.
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Once you close the viewing application the whole DisposableVM will be destroyed.
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If you have edited the file and saved the changes, the changed file will be saved back to the original AppVM, overwriting the original.
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## Opening a fresh web browser instance in a new DisposableVM ##
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Sometimes it is desirable to open an instance of Firefox within a new fresh DisposableVM.
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This can be done easily using the Start Menu: just go to **Application Menu -\> DisposableVM -\> DisposableVM:Firefox web browser**.
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Wait a few seconds until a web browser starts.
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Once you close the viewing application the whole DisposableVM will be destroyed.
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## Opening a file in a DisposableVM via command line (from AppVM) ##
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Use the `qvm-open-in-dvm` command from a terminal in your AppVM:
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~~~
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[user@work-pub ~]$ qvm-open-in-dvm Downloads/apple-sandbox.pdf
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~~~
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Note that the `qvm-open-in-dvm` process will not exit until you close the application in the DisposableVM.
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## Starting an arbitrary program in a DisposableVM from an AppVM ##
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Sometimes it can be useful to start an arbitrary program in a DisposableVM.
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This can be done from an AppVM by running
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~~~
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[user@vault ~]$ qvm-run '@dispvm' xterm
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~~~
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The created DisposableVM can be accessed via other tools (such as `qvm-copy-to-vm`) using its `disp####` name as shown in the Qubes Manager or `qvm-ls`.
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## Starting an arbitrary application in a DisposableVM via command line from dom0 ##
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The Application Launcher has shortcuts for opening a terminal and a web browser in dedicated DisposableVMs, since these are very common tasks.
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However, it is possible to start an arbitrary application in a DisposableVM directly from dom0 by running:
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~~~
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$ qvm-run --dispvm=dvm-template --service qubes.StartApp+xterm
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~~~
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The label color will be inherited from the `dvm-template`.
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(The DisposableVM Application Launcher shortcut used for starting programs runs a very similar command to the one above.)
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### Opening a link in a DisposableVM based on a non-default DisposableVM Template from a qube ###
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Suppose that the default DisposableVM Template for your `email` qube has no networking (e.g., so that untrusted attachments can't phone home).
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However, sometimes you want to open email links in DisposableVMs.
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Obviously, you can't use the default DisposableVM Template, since it has no networking, so you need to be able to specify a different DisposableVM Template.
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You can do that with this command from the `email` qube (as long as your RPC policies allow it):
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~~~
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$ qvm-open-in-vm @dispvm:online-dvm-template https://www.qubes-os.org
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~~~
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This will create a new DisposableVM based on `online-dvm-template`, open the default web browser in that DisposableVM, and navigate to `https://www.qubes-os.org`.
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#### Example of RPC policies to allow this behavior
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In dom0, add the following line at the beginning of the file `/etc/qubes-rpc/policy/qubes.OpenURL`
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~~~
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@anyvm @dispvm:online-dvm-template allow
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~~~
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This line means:
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- FROM: Any VM
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- TO: A DisposableVM based on the `online-dvm-template` TemplateVM
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- WHAT: Allow sending an "Open URL" request
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In other words, any VM will be allowed to create a new DisposableVM based on `online-dvm-template` and open a URL inside of that DisposableVM.
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More information about RPC policies for DisposableVMs can be found [here][qrexec].
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## Customizing DisposableVMs ##
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You can change the template used to generate the DisposableVMs, and change settings used in the DisposableVM savefile.
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These changes will be reflected in every new DisposableVM based on that template.
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Full instructions can be found [here](/doc/disposablevm-customization/).
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[DisposableVM Template]: /doc/glossary/#disposablevm-template
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[qrexec]: /doc/qrexec/#qubes-rpc-administration
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