Memory Technology Device

The MTD subsystem was created to provide an abstraction layer between the hardware-specific device drivers and higher-level applications.

USB sticks, MMCs, SDs, CompactFlashes and other popular removable devices are not MTDs.

The MTD subsystem exports block devices as well, which allows the use of common filesystem like ext4.

However, using an MTD this way is not recommended since there is neither detection of bad blocks nor any kind of wear leveling.

MTDs don't address to the kernel like traditional storage devices (Solid State Drive, Hard Disk Drive...) using LBAs, but rather using offsets and sizes.