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The Device-mapper is a generic framework to map one block device into another in Linux kernel. It forms the foundation of LVM2 and EVMS, software RAIDs, Cryptoloop file system encryption, and offers additional features such as file system snapshots.

Device-mapper works by processing data passed in from a virtual block device, that it itself provides, and then passing it on to another block device.

Applications (like LVM2 and EVMS) that want to create new mapped devices talk to the Device-mapper via the libdevmapper.so shared library, which in turn issues ioctls to the /dev/mapper/control device node. Device-mapper is also accessible from shell scripts via the dmsetup tool.

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