Chapter 16. Unmapping a Block Device
To unmap a block device image with the rbd command, specify the unmap option and the device name (i.e. by convention the same as the block device image name).
To do so, execute the following:
sudo rbd unmap /dev/rbd/{poolname}/{imagename}
sudo rbd unmap /dev/rbd/{poolname}/{imagename}
For example:
sudo rbd unmap /dev/rbd/rbd/foo
sudo rbd unmap /dev/rbd/rbd/foo