Device mapper

The device mapper is a framework provided by the Linux kernel for mapping physical block devices onto higher-level virtual block devices. It forms the foundation of the logical volume manager (LVM), software RAIDs and dm-crypt disk encryption, and offers additional features such as file system snapshots. Device mapper works by passing data from a virtual block device, which is provided by the device mapper itself, to another block device. Data can be also modified in transition, which is performed, for example, in the case of device mapper providing disk encryption or simulation of unreliable hardware behavior. This article focuses on the device mapper implementation in the Linux kernel, but the device mapper functionality is also available in both NetBSD and DragonFly BSD.

The device mapper is a framework provided by the Linux kernel for mapping physical block devices onto higher-level virtual block devices. It forms the foundation of the logical volume manager (LVM), software RAIDs and dm-crypt disk encryption, and offers additional features such as file system snapshots. Device mapper works by passing data from a virtual block device, which is provided by the device mapper itself, to another block device. Data can be also modified in transition, which is performed, for example, in the case of device mapper providing disk encryption or simulation of unreliable hardware behavior. This article focuses on the device mapper implementation in the Linux kernel, but the device mapper functionality is also available in both NetBSD and DragonFly BSD. == Applications == Linux kernel features and projects built on top of the device mapper include the following: cryptsetup utility used to conveniently setup disk encryption based on dm-crypt dm-crypt/LUKS mapping target that provides volume encryption dm-cache mapping target that allows creation of hybrid volumes dm-integrity mapping target that provides data integrity, either using checksumming or cryptographic verification, also used with LUKS dm-log-writes mapping target that uses two devices, passing through the first device and logging the write operations performed to it on the second device dm-verity validates the data blocks contained in a file system against a list of cryptographic hash values, developed as part of the ChromiumOS project provides access to "fake" RAID configurations via the device mapper DM Multipath provides I/O failover and load-balancing of block devices within the Linux kernel Docker uses device mapper to create copy-on-write storage for software containers DRBD (Distributed Replicated Block Device) EVMS (deprecated) utility called from hotplug upon device maps creation and deletion LVM2 logical volume manager for the Linux kernel VeraCrypt - Linux version of TrueCrypt VDO - Virtual Data Optimizer

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