SD(4)                     (2017-09-15)                      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 corre-
          sponds 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 1en4 are the DOS "primary" partitions

               partitions 5en8 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;
              };

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     SD(4)                     (2017-09-15)                      SD(4)

               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 geome-
               try 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 5.10 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/.

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