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

       sd - driver for SCSI disk drives

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

       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.

       The following ioctls are provided:

              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 ge-
              ometry information is not available, zero will be  returned  for
              all of the parameters.

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

              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.

              the whole device

              individual block partitions

       This  page  is  part of release 5.05 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

Linux                             2017-09-15                             SD(4)
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