Qubes Windows Tools: advanced settings and troubleshooting

This document only applies to Qubes R3 (tools version 3.x) Only 64-bit Windows 7 (any edition) is supported currently.

Installable components

Qubes Windows Tools (QWT for short) contain several components than can be enabled or disabled during installation:

  • Shared components (required): common libraries used by QWT components.
  • Xen PV drivers: drivers for the virtual hardware exposed by Xen.
    • Base Xen PV Drivers (required): paravirtual bus and interface drivers.
    • Xen PV Disk Drivers: paravirtual storage drivers.
    • Xen PV Network Drivers: paravirtual network drivers.
  • Qubes Core Agent: qrexec agent and services. Needed for proper integration with Qubes.
    • Move user profiles: user profile directory (c:\users) is moved to VM’s private disk backed by private.img file in dom0 (useful mainly for HVM templates).
  • Qubes GUI Agent: video driver and gui agent that enable seamless showing of Windows applications on the secure Qubes desktop.
  • Disable UAC: User Account Control may interfere with QWT and doesn’t really provide any additional benefits in Qubes environment.

In testing VMs only it’s probably a good idea to install a VNC server before installing QWT. If something goes very wrong with the Qubes gui agent, a VNC server should still allow access to the OS.

NOTE: Xen PV disk drivers are not installed by default. This is because they seem to cause problems (BSOD = Blue Screen Of Death). We’re working with upstream devs to fix this. However, the BSOD seems to only occur after the first boot and everything works fine after that. Enable the drivers at your own risk of course, but we welcome reports of success/failure in any case (backup your VM first!). With disk PV drivers absent qvm-block will not work for the VM, but you can still use standard Qubes inter-VM file copying mechanisms.

Xen PV driver components may display a message box asking for reboot during installation – it’s safe to ignore them and defer the reboot.

Installation logs

If the install process fails or something goes wrong during it, include the installation logs in your bug report. They are created in the %TEMP% directory, by default <user profile>\AppData\Local\Temp. There are two text files, one small and one big, with names starting with Qubes_Windows_Tools.

Uninstalling QWT is supported from version 3.2.1. Uninstalling previous versions is not recommended. After uninstalling you need to manually enable the DHCP Client Windows service, or set IP settings yourself to restore network access.


Starting from version 2.2.* various aspects of Qubes Windows Tools can be configured through registry. Main configuration key is located in HKEY_LOCAL_MACHINE\SOFTWARE\Invisible Things Lab\Qubes Tools. Configuration values set on this level are global to all QWT components. It’s possible to override global values with component-specific keys, this is useful mainly for setting log verbosity for troubleshooting. Possible configuration values are:

Name Type Description Default value
LogDir String Directory where logs are created c:\Program Files\Invisible Things Lab\Qubes Tools\log
LogLevel DWORD Log verbosity (see below) 2 (INFO)
LogRetention DWORD Maximum age of log files (in seconds), older logs are automatically deleted 604800 (7 days)

Possible log levels:

1 Error Serious errors that most likely cause irrecoverable failures
2 Warning Unexpected but non-fatal events
3 Info Useful information (default)
4 Debug Internal state dumps for troubleshooting
5 Verbose Trace most function calls

Debug and Verbose levels can generate large volume of logs and are intended for development/troubleshooting only.

To override global settings for a specific component, create a new key under the root key mentioned above and name it as the executable name, without .exe extension. For example, to change qrexec-agent’s log level to Debug, set it like this:


Component-specific settings currently available:

Component Setting Type Description Default value
qga DisableCursor DWORD Disable cursor in the VM. Useful for integration with Qubes desktop so you don’t see two cursors. Can be disabled if you plan to use the VM through a remote desktop connection of some sort. Needs gui agent restart to apply change (locking OS/logoff should be enough since qga is restarted on desktop change). 1


If the VM is inaccessible (doesn’t respond to qrexec commands, gui is not functioning), try to boot it in safe mode:

  • qvm-start --debug vmname
  • mash F8 on the boot screen to enable boot options and select Safe Mode (optionally with networking)

Safe Mode should at least give you access to logs (see above).

Please include appropriate logs when reporting bugs/problems. Starting from version 2.4.2 logs contain QWT version, but if you’re using an earlier version be sure to mention which one. If the OS crashes (BSOD) please include the BSOD code and parameters in your bug report. The BSOD screen should be visible if you run the VM in debug mode (qvm-start --debug vmname). If it’s not visible or the VM reboots automatically, try to start Windows in safe mode (see above) and 1) disable automatic restart on BSOD (Control Panel - System - Advanced system settings - Advanced - Startup and recovery), 2) check the system event log for BSOD events. If you can, send the memory.dmp dump file from c:\Windows. Xen logs (/var/log/xen/console/guest-*) are also useful as they contain pvdrivers diagnostic output.

If a specific component is malfunctioning, you can increase its log verbosity as explained above to get more troubleshooting information. Below is a list of components:

qrexec-agent Responsible for most communication with Qubes (dom0 and other domains), secure clipboard, file copying, qrexec services.
qrexec-wrapper Helper executable that’s responsible for launching qrexec services, handling their I/O and vchan communication.
qrexec-client-vm Used for communications by the qrexec protocol.
qga Gui agent.
QgaWatchdog Service that monitors session/desktop changes (logon/logoff/locking/UAC…) and simulates SAS sequence (ctrl-alt-del).
qubesdb-daemon Service for accessing Qubes configuration database.
network-setup Service that sets up network parameters according to VM’s configuration.
prepare-volume Utility that initializes and formats the disk backed by private.img file. It’s registered to run on next system boot during QWT setup, if that feature is selected (it can’t run during the setup because Xen block device drivers are not yet active). It in turn registers move-profiles (see below) to run at early boot.
relocate-dir Utility that moves user profiles directory to the private disk. It’s registered as an early boot native executable (similar to chkdsk) so it can run before any profile files are opened by some other process. Its log is in a fixed location: c:\move-profiles.log (it can’t use our common logger library so none of the log settings apply).


When we publish new QWT version (which is announced on qubes-users Google Group) it’s usually pushed to the current-testing or unstable repository first. To use versions from current-testing, run this in dom0:

qubes-dom0-update --enablerepo=qubes-dom0-current-testing qubes-windows-tools

That command will download a new QWT .iso from the testing repository. It goes without saying that you should backup your VMs before installing anything from testing repos.