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191 lines
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Markdown
191 lines
10 KiB
Markdown
---
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lang: en
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layout: doc
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permalink: /doc/how-to-use-disposables/
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redirect_from:
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- /doc/how-to-use-disposablevms/
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- /doc/disposable/
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- /doc/disposablevm/
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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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ref: 203
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title: How to use disposables
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---
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A [disposable](/doc/glossary/#disposable) is a lightweight [qube](/doc/glossary/#qube) that can be created quickly and will self-destruct when closed.
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Disposables are usually created in order to host a single application, like a viewer, editor, or web browser.
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From inside an app qube, choosing the `Open in disposable` option on a file will launch a disposable for just that file.
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Changes made to a file opened in a disposable 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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Disposables can be launched either directly from dom0's Start Menu or terminal window, or from within app qubes.
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While running, disposables will appear in Qubes VM Manager with the name `disp####`.
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[](/attachment/doc/disposablevm-example.png)
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This diagram provides a general example of how disposables can be used to safely open untrusted links and attachments in disposables. See [this article](https://blog.invisiblethings.org/2010/06/01/disposable-vms.html) for more on why one would want to use a disposable.
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## Security
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If a [disposable template](/doc/glossary/#disposable-template) becomes compromised, then any disposable based on that disposable template could be compromised.
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In particular, the *default* disposable template is important because it is used by the "Open in disposable" 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 disposable template on a trusted template.
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### Disposables and Local Forensics
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At this time, disposables 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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## Disposables and Networking
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Similarly to how app qubes are based on their underlying [template](/doc/glossary/#template), disposables are based on their underlying [disposable template](/doc/glossary/#disposable-template).
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R4.0 introduces the concept of multiple disposable templates, whereas R3.2 was limited to only one.
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On a fresh installation of Qubes, the default disposable template is called `fedora-XX-dvm` (where `XX` is the Fedora version of the default template).
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If you have included the Whonix option in your install, there will also be a `whonix-ws-dvm` disposable template available for your use.
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You can set any app qube to have the ability to act as a disposable template with:
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```
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qvm-prefs <vmname> template_for_dispvms True
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```
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The default system wide disposable template can be changed with `qubes-prefs default_dispvm`.
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By combining the two, choosing `Open in disposable` from inside an app qube will open the document in a disposable based on the default disposable 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 disposable" setting to specify which disposable template will be used to launch disposables from that VM.
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This can also be changed from the command line with:
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```
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qvm-prefs <VM> default_dispvm <DISPOSABLEVM_TEMPLATE>
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```
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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 app qube that has also been configured as a disposable template to use itself, so disposables launched from within the app qube/disposable template would inherit the same settings.
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NetVM and firewall rules for disposable templates can be set as they can for a normal VM.
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By default a disposable will inherit the NetVM and firewall settings of the disposable template on which it is based.
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This is a change in behaviour from R3.2, where disposables would inherit the settings of the app qube from which they were launched.
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Therefore, launching a disposable from an app qube will result in it using the network/firewall settings of the disposable template on which it is based.
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For example, if an app qube uses sys-net as its NetVM, but the default system disposable uses sys-whonix, any disposable launched from this app qube 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 disposable uses sys-net, launching a disposable from inside anon-whonix will result in the disposable using sys-net.
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A disposable launched from the Start Menu inherits the NetVM and firewall settings of the disposable template on which it is based.
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Note that changing the "NetVM" setting for the system default disposable template *does* affect the NetVM of disposables launched from the Start Menu.
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Different disposable templates with individual NetVM settings can be added to the Start Menu.
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**Important Notes:**
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Some disposable templates will automatically create a menu item to launch a disposable, if you do not see an entry and want to add one please use the command:
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```
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qvm-features <DISPOSABLE> appmenus-dispvm 1
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```
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To launch a disposable template from the command line, in dom0 please type the following:
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```
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qvm-run --dispvm=<DISPOSABLE_TEMPLATE> --service qubes.StartApp+NameOfApp
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```
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## Opening a file in a disposable via GUI
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In an app qube's file manager, right click on the file you wish to open in a disposable, then choose "View in disposable" or "Edit in disposable".
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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 disposable created for the purpose of viewing or editing this very file.
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Once you close the viewing application the whole disposable 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 app qube, overwriting the original.
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## Opening a fresh web browser instance in a new disposable
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Sometimes it is desirable to open an instance of Firefox within a new fresh disposable.
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This can be done easily using the Start Menu: just go to **Application Menu -\> Disposable -\> Disposable: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 disposable will be destroyed.
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## Opening a file in a disposable via command line (from app qube)
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Use the `qvm-open-in-dvm` command from a terminal in your app qube:
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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 disposable.
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## Starting an arbitrary program in a disposable from an app qube
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Sometimes it can be useful to start an arbitrary program in a disposable.
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The disposable will stay running so long as the process which started the disposable has not exited.
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Some applications, such as GNOME Terminal, do not wait for the application to close before the process exits (details [here](https://github.com/QubesOS/qubes-issues/issues/2581#issuecomment-272664009)).
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Starting an arbitrary program can be done from an app qube 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 disposable 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 disposable via command line from dom0
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The Application Launcher has shortcuts for opening a terminal and a web browser in dedicated disposables, since these are very common tasks.
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The disposable will stay running so long as the process which started the disposable has not exited.
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Some applications, such as GNOME Terminal, do not wait for the application to close before the process exits (details [here](https://github.com/QubesOS/qubes-issues/issues/2581#issuecomment-272664009)).
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It is possible to start an arbitrary application in a disposable directly from dom0 by running:
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~~~
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$ qvm-run --dispvm=<DISPOSABLE_TEMPLATE> --service qubes.StartApp+xterm
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~~~
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The label color will be inherited from `<DISPOSABLE_TEMPLATE>`.
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(The disposable 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 disposable based on a non-default disposable template from a qube
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Suppose that the default disposable 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 disposables.
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Obviously, you can't use the default disposable template, since it has no networking, so you need to be able to specify a different disposable 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_DISPOSABLE_TEMPLATE> https://www.qubes-os.org
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~~~
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This will create a new disposable based on `<ONLINE_DISPOSABLE_TEMPLATE>`, open the default web browser in that disposable, 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_DISPOSABLE_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 disposable based on `<ONLINE_DISPOSABLE_TEMPLATE>`
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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 disposable based on `<ONLINE_DISPOSABLE_TEMPLATE>` and open a URL inside of that disposable.
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More information about RPC policies for disposables can be found [here](/doc/qrexec/#qubes-rpc-administration).
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## Customizing disposables
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You can change the template used to generate the disposables, and change settings used in the disposable savefile.
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These changes will be reflected in every new disposable based on that template.
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Full instructions can be found [here](/doc/disposable-customization/).
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