How To Restore DVD & Removable Drive

Restore the DVD drive:
# xe sr-create host-uuid= content-type=iso name-label=”DVD drives” type=udev device-config:location=/dev/xapi/cd

Restore removable storage:
# xe sr-create host-uuid= content-type=disk name-label=”Removable storage” type=udev device-config:location=/dev/xapi/block

Source: http://support.citrix.com/article/CTX120962