The Linux Kernel Device Mapper is the LVM (Linux Logical Volume Management)
 Team's implementation of a minimalistic kernel-space driver that handles
 volume management, while keeping knowledge of the underlying device layout
 in user-space. This makes it useful for not only LVM, but software raid,
 and other drivers that create "virtual" block devices.
 .
 This package contains the (user-space) header files for accessing the
 device-mapper; it allow usage of the device-mapper through a clean,
 consistent interface (as opposed to through kernel ioctls).