When the webcam is detached from the host the emulated webcam device is automatically detached from the guest only if the webcam is streaming video. If the emulated webcam is inactive it should be manually detached using the VBoxManage controlvm VM-name webcam detach command.

Aliases .0 and .1 are mapped to /dev/video0, alias .2 is mapped to /dev/video1 and so forth.