A.5 Device Mapper

  • The always writable feature indicates that a target does not support read-only mode. (3.2)

  • The immutable feature indicates that a target type cannot be mixed with any other target type. Once loaded into a device, it cannot be replaced with a table that contains a different type. (3.2)

  • Add a singleton table that can contain only one target. (3.2)

  • Log device dependency allows registration of a log device so that it is included in the list of device dependencies. (3.2)

  • A verity target allows a device to store cryptographic hashes of file system blocks. The device can be used to check every read of the file system. If the hash of the block does not match that of the file system, the read fails. (3.4)