Device Control on a Linux Host
On Linux hosts, guest operating systems can use devices that are not already in use by the host — that is, devices that are not claimed by a host operating system driver.
If your device is in use by the host and you try to connect it to the guest using the VM > Removable Devices menu, a dialog box appears, informing you that there is a problem connecting to the device.
To disconnect the device from the host, you must unload the device driver. You can unload the driver manually as root (su -) using the rmmod command. If the driver was automatically loaded by hotplug, you can disable it in the hotplug configuration files in the /etc/hotplug directory. See your Linux distribution’s documentation for details on editing these configuration files.
A related issue sometimes affects devices that rely on automatic connection (as PDAs often do).
If you have successfully used autoconnection to connect the device to your virtual machine, and later experience problems with the connection to the device, complete the following steps:
1

Disconnect and reconnect the device. You can either unplug it physically, and plug it back in, or use the VM > Removable Devices menu to disconnect it and reconnect it.
2

If you see a dialog box warning that the device is in use, disable it in the hotplug configuration files in the /etc/hotplug directory.