Currently (until issue [1082](https://github.com/QubesOS/qubes-issues/issues/1082) gets implemented), if you remove the device before detaching it from the qube, Qubes OS (more precisely, `libvirtd`) will think that the device is still attached to the qube and will not allow attaching further devices under the same name.
This may be characterized by VM manager crashes and the error message: `Houston, we have a problem`.
If this isn't an option, you can manually recover from the situation by following the instructions at the [Block Devices documentation](/doc/block-devices/#what-if-i-removed-the-device-before-detaching-it-from-the-vm)
## "Device attach failed" error
Upon trying to attach a USB device using the `qvm-usb -a vm-name device-vm-name:device` command, you may face the error `Device attach failed: no device info received, connection failed, check backend side for details`.
## usbVM does not boot after creating and assigning USB controllers to it ##
This is probably because one of the controllers does not support reset.
In Qubes R2 any such errors were ignored. In Qubes R3.x they are not.
In R4.x, devices that are automatically added to sys-net and sys-usb on install but do not support FLR will be attached with the no-strict-reset option, but see the related warning in the last sentence in this answer.
A device that does not support reset is not ideal and generally should not be assigned to a VM.
Most likely the offending controller is a USB 3.0 device.
You can remove this controller from the usbVM, and see if this allows the VM to boot.
Alternatively you may be able to disable USB 3.0 in the BIOS.
If the BIOS does not have the option to disable USB 3.0, try running the following command in dom0 to [force USB 2.0 modes for the USB ports][force_usb2]:
- In Qubes R3.x, by modifying the VM's properties:
qvm-prefs usbVM -s pci_strictreset false
These options allow the VM to ignore the error and the VM will start.
Please review the notes in the `qvm-prefs` man page and [here][assign_devices] and be aware of the potential risks.
## Can't use keyboard or mouse after creating sys-usb ##
You risk locking yourself out of your computer if you have a USB keyboard and use full disk encryption alongside sys-usb.
On boot, the keyboard may be inactive, preventing you from entering your LUKS decryption password.
When you enable a USB qube, it hides all the USB controllers from dom0, even before it gets started.
So, if your only keyboard is on USB, you should undo this hiding.
To solve the problem, disable the USB qube by not having it autostart, or unassigning your USB controller(s) from it. If you had created the USB qube by checking the box in the installer, then your USB controller(s) are probably hidden from dom0. To unhide them, reverse the procedure described in the [USB Qubes documentation](https://www.qubes-os.org/doc/usb-qubes/#how-to-hide-all-usb-controllers-from-dom0) (under "How to hide all USB controllers from dom0"). That is, remove `rd.qubes.hide_all_usb`, instead of adding it.
Note that this procedure will attach your USB controllers to dom0, so do this only with USB devices you trust.
If your computer has a PS/2 port, you may instead use a PS/2 keyboard to enter the LUKS password.
