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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 partition 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_number 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

Linux                                                                          2017-09-15                                                                          SD(4)