Cddvd.nss is loaded automatically on startup by default. Cddvd.nss provides the following commands for adding and removing CD and DVD image files as NSS Volumes.
While the CD or DVD image source file is loaded as an NSS volume, the following actions cause the image file to be removed as an NSS volume:
Any file operations on the image source file, such as open, read, or write
Deactivation of the NSS volume where the image source file resides