raw

raw /dev/raw/rawN major minorraw /dev/raw/rawN /dev/blockdevraw -q [-a] [rawN]

raw binds Linux raw character devices to block devices, allowing direct (unbuffered) I/O access to the underlying storage. Raw devices bypass the kernel's buffer cache, providing direct access to block devices for applications that manage their own caching (like databases).When a raw device is bound to a block device, reading and writing to the raw device performs synchronous, direct I/O to the underlying storage without kernel buffering.

/dev/raw/rawN

Raw device node to bind or query

Query binding for specified raw device

Query all raw devices (with -q)

Block device specified by major/minor numbers

Block device path to bind to raw device

Raw devices are largely deprecated in favor of O_DIRECT flag on regular file I/O. Requires the raw driver to be loaded (modprobe raw). Raw device nodes must exist in /dev/raw/ before binding. Only root can bind raw devices.

Raw devices were introduced in Linux 2.4 to support databases like Oracle that required unbuffered I/O. The O_DIRECT flag added in later kernels provides similar functionality without dedicated raw devices, making this interface largely obsolete.

losetup(8), dd(1), blockdev(8)