Disposable VM Customization

Changing the DVM Template

You may want to use a non-default template the DVM Template. One example is to use a less-trusted template with some less trusted, 3rd party, often unsigned, applications installed, such as e.g. 3rd part printer drivers.

In order to regenerate the Disposable VM “snapshot” (called ‘savefile’ on Qubes) one can use the following command in Dom0:

[user@dom0 ~]$ qvm-create-default-dvm <custom-template-name>

This would create a new Disposable VM savefile based on the custom template. For example <custom-template-name> could be the name of the existing debian-8 vm, which creates the disposable vm debain-8-dvm. Now, whenever one opens a file (from any AppVM) in a Disposable VM, a Disposable VM based on this template will be used.

One can easily verify if the new Disposable VM template is indeed based on a custom template (in the example below the template called “f17-yellow” was used as a basis for the Disposable VM):

[user@dom0 ~]$ ll /var/lib/qubes/dvmdata/
total 0
lrwxrwxrwx 1 user user 45 Mar 11 13:59 default_dvm.conf -> /var/lib/qubes/appvms/f17-yellow-dvm/dvm.conf
lrwxrwxrwx 1 user user 49 Mar 11 13:59 default_savefile -> /var/lib/qubes/appvms/f17-yellow-dvm/dvm-savefile
lrwxrwxrwx 1 user user 47 Mar 11 13:59 savefile_root -> /var/lib/qubes/vm-templates/f17-yellow/root.img

If you wish to use the fedora-minimal template as a DVM Template, see the “DVM Template” use case under fedora-minimal customization.

Customization of Disposable VM

It is possible to change the settings of each new Disposable VM (DispVM). This can be done by customizing the DispVM template:

  1. Start a terminal in the fedora-23-dvm TemplateVM by running the following command in a dom0 terminal. (By default, this TemplateVM is not shown in Qubes VM Manager. However, it can be shown by selecting “Show/Hide internal VMs.”)

    [user@dom0 ~]$ qvm-run -a fedora-23-dvm gnome-terminal
    
  2. Change the VM’s settings and/or applications, as desired. Note that currently Qubes supports exactly one DispVM template, so any changes you make here will affect all DispVMs. Some examples of changes you may want to make include:
    • Changing Firefox’s default startup settings and homepage.
    • Changing Nautilus’ default file preview settings.
    • Changing the DispVM’s default NetVM. For example, you may wish to set the NetVM to “none.” Then, whenever you start a new DispVM, you can choose your desired ProxyVM manually (by changing the newly-started DipsVMs settings). This is useful if you sometimes wish to use a DispVM with a TorVM, for example. It is also useful if you sometimes wish to open untrusted files in a network-disconnected DispVM.
  3. Create an empty /home/user/.qubes-dispvm-customized file in the VM (not in dom0):

    [user@fedora-23-dvm ~]$ touch /home/user/.qubes-dispvm-customized
    
  4. Shutdown the VM (either by poweroff from VM terminal, or qvm-shutdown from dom0 terminal).
  5. Regenerate the DispVM template using the default template:

    [user@dom0 ~]$ qvm-create-default-dvm --default-template
    

    Or, if you’re using a non-default template, regenerate the DispVM using your custom template:

    [user@dom0 ~]$ qvm-create-default-dvm <custom-template-name>
    

Note: All of the above requires at least qubes-core-vm >= 2.1.2 installed in template.

Adding arbitrary programs to Disposable VM Application Menu

For added convenience, arbitrary programs can be added to the Application Menu of the Disposable VM. In order to do that create (e.g.) arbitrary.desktop file in /usr/share/applications in Dom0. That file will point to the desired program. Use the following template for the file:

[Desktop Entry]
Version=1.0
Type=Application
Exec=sh -c 'echo arbitrary | /usr/lib/qubes/qfile-daemon-dvm qubes.VMShell dom0 DEFAULT red'
Icon=dispvm-red
Terminal=false
Name=DispVM: Arbitrary Name
GenericName=DispVM: Arbitrary Generic Name
StartupNotify=false
Categories=Network;X-Qubes-VM;

Next, the /etc/xdg/menus/applications-merged/qubes-dispvm.menu file has to be modified so that it points to the newly-created .desktop file. (If you use i3 you can skip this step; the shortcut gets added to dmenu automatically.)

Add a <Filename>arbitrary.desktop</Filename> line so that your modified file looks like this:

<Include>
<Filename>qubes-dispvm-firefox.desktop</Filename>
<Filename>qubes-dispvm-xterm.desktop</Filename>
<Filename>arbitrary.desktop</Filename>
</Include>

After saving the changes the new shortcut should appear in the Disposable VM Applications menu.