I'm running Bazzite and installed Virtual Machine Manager through Flatpak, along with the QEMU add-on. I'm trying to redirect a USB drive into a Windows 10 virtual machine so I can access installation files, but VMM fails with "Insufficient Permission [-3] (0)." My main account has administrator privileges. Could the Flatpak sandbox be blocking USB access, or do I also need to install and configure libvirt? What permissions or group memberships are required?
3 Answers
Make sure the virtualization service is installed and running, and that your user has been added to the appropriate libvirt group. After adding yourself, log out and back in—or reboot—so the new group membership takes effect. Then check that VMM is connected to the correct libvirt session and that the USB drive is not mounted or being used by the host when you try to attach it.
This is most likely the Flatpak sandbox rather than ordinary administrator privileges. Open Flatseal, select Virtual Machine Manager, and enable access to USB devices—typically the Devices permission such as “All devices.” You may also need access to the libvirt connection/socket used by your setup. Restart VMM completely after changing the permissions. Installing libvirt alone will not automatically grant a sandboxed Flatpak access to host USB devices.
If Flatseal permissions still do not solve it, try the distribution’s native VMM/libvirt packages instead of the Flatpak. USB passthrough can be affected by both the sandbox and host udev permissions, so using the native package may avoid the extra permission layer. Also, attach the physical USB device through the VM’s hardware settings rather than trying to pass through a mounted filesystem.
So the important part is enabling device access for the VMM Flatpak, not just adding my account to the libvirt group? I’ll restart the application after changing that.