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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:

       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
	      geometry 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)
	      will fail with the error EINVAL.

       /dev/sd[a-h]: the whole device
       /dev/sd[a-h][0-8]: individual block partitions

       This  page  is  part of release 4.10 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

Linux				  2012-05-03				 SD(4)