SD(4)							     Linux Programmer's Manual							     SD(4)

NAME

       sd - driver for SCSI disk drives

SYNOPSIS

       #include <linux/hdreg.h>        /* for HDIO_GETGEO */
       #include <linux/fs.h>	       /* for BLKGETSIZE and BLKRRPART */

CONFIGURATION

       The  block device name has the following form: sdlp, where l is a letter denoting the physical drive, and p is a number denoting the parti-
       tion on that physical drive.  Often, the partition number, p, will be left off when the device corresponds to the whole drive.

       SCSI disks have a major device number of 8, and a minor device number of the form (16 * drive_number) + partition_number, where	drive_num-
       ber is the number of the physical drive in order of detection, and partition_number is as follows:

       +3     partition 0 is the whole drive

	      partitions 1-4 are the DOS "primary" partitions

	      partitions 5-8 are the DOS "extended" (or "logical") partitions

       For  example,  /dev/sda	will  have  major 8, minor 0, and will refer to all of the first SCSI drive in the system; and /dev/sdb3 will have
       major 8, minor 19, and will refer to the third DOS "primary" partition on the second SCSI drive in the system.

       At this time, only block devices are provided.  Raw devices have not yet been implemented.

DESCRIPTION

       The following ioctls are provided:

       HDIO_GETGEO
	      Returns the BIOS disk parameters in the following structure:

	   struct hd_geometry {
	       unsigned char  heads;
	       unsigned char  sectors;
	       unsigned short cylinders;
	       unsigned long  start;
	   };

	      A pointer to this structure is passed as the ioctl(2) parameter.

	      The information returned in the parameter is the disk geometry of the drive as understood by DOS!  This geometry is not the physical
	      geometry of the drive.  It is used when constructing the drive's partition table, however, and is needed for convenient operation of
	      fdisk(1), efdisk(1), and lilo(1).  If the geometry information is not available, zero will be returned for all of the parameters.

       BLKGETSIZE
	      Returns the device size in sectors.  The ioctl(2) parameter should be a pointer to a long.

       BLKRRPART
	      Forces a reread of the SCSI disk partition tables.  No parameter is needed.

	      The SCSI ioctl(2) operations are also supported.	If the ioctl(2) parameter is required, and it is NULL, then  ioctl(2)  fails  with
	      the error EINVAL.

FILES

       /dev/sd[a-h]
	      the whole device

       /dev/sd[a-h][0-8]
	      individual block partitions

COLOPHON

       This  page is part of release 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Linux								    2017-09-15								     SD(4)