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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  parti-
     tion_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 conve-
            nient 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 4.16 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)