man4/sd.4

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   2 .\" Copyright 1992 Rickard E. Faith (faith@cs.unc.edu)
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  26 .TH SD 4 2017-09-15 "Linux" "Linux Programmer's Manual"
  27 .SH NAME
  28 sd \- driver for SCSI disk drives
  29 .SH SYNOPSIS
  30 .nf
  31 .BR "#include <linux/hdreg.h>        " "/* for HDIO_GETGEO */"
  32 .BR "#include <linux/fs.h>           " "/* for BLKGETSIZE and BLKRRPART */"
  33 .fi
  34 .SH CONFIGURATION
  35 The block device name has the following form:
  36 .BI sd lp,
  37 where
  38 .I l
  39 is a letter denoting the physical drive, and
  40 .I p
  41 is a number denoting the partition on that physical drive.
  42 Often, the partition number,
  43 .IR p ,
  44 will be left off when the device corresponds to the whole drive.
  45 .PP
  46 SCSI disks have a major device number of 8, and a minor device number of
  47 the form (16 *
  48 .IR drive_number ") + " partition_number ,
  49 where
  50 .I drive_number
  51 is the number of the physical drive in order of detection, and
  52 .I partition_number
  53 is as follows:
  54 .IP +3
  55 partition 0 is the whole drive
  56 .IP
  57 partitions 1\(en4 are the DOS "primary" partitions
  58 .IP
  59 partitions 5\(en8 are the DOS "extended" (or "logical") partitions
  60 .PP
  61 For example,
  62 .I /dev/sda
  63 will have major 8, minor 0, and will refer to all of the first SCSI drive
  64 in the system; and
  65 .I /dev/sdb3
  66 will have major 8, minor 19, and will refer to the third DOS "primary"
  67 partition on the second SCSI drive in the system.
  68 .PP
  69 At this time, only block devices are provided.
  70 Raw devices have not yet been implemented.
  71 .SH DESCRIPTION
  72 The following
  73 .IR ioctl s
  74 are provided:
  75 .TP
  76 .B HDIO_GETGEO
  77 Returns the BIOS disk parameters in the following structure:
  78 .PP
  79 .in +4n
  80 .EX
  81 struct hd_geometry {
  82     unsigned char  heads;
  83     unsigned char  sectors;
  84     unsigned short cylinders;
  85     unsigned long  start;
  86 };
  87 .EE
  88 .in
  89 .IP
  90 A pointer to this structure is passed as the
  91 .BR ioctl (2)
  92 parameter.
  93 .IP
  94 The information returned in the parameter is the disk geometry of the drive
  95 .I "as understood by DOS!"
  96 This geometry is
  97 .I not
  98 the physical geometry of the drive.
  99 It is used when constructing the
 100 drive's partition table, however, and is needed for convenient operation
 101 of
 102 .BR fdisk (1),
 103 .BR efdisk (1),
 104 and
 105 .BR lilo (1).
 106 If the geometry information is not available, zero will be returned for all
 107 of the parameters.
 108 .TP
 109 .B BLKGETSIZE
 110 Returns the device size in sectors.
 111 The
 112 .BR ioctl (2)
 113 parameter should be a pointer to a
 114 .IR long .
 115 .TP
 116 .B BLKRRPART
 117 Forces a reread of the SCSI disk partition tables.
 118 No parameter is needed.
 119 .IP
 120 The SCSI
 121 .BR ioctl (2)
 122 operations are also supported.
 123 If the
 124 .BR ioctl (2)
 125 parameter is required, and it is NULL, then
 126 .BR ioctl (2)
 127 fails with the error
 128 .BR EINVAL .
 129 .SH FILES
 130 .TP
 131 .I /dev/sd[a\-h]
 132 the whole device
 133 .TP
 134 .I /dev/sd[a\-h][0\-8]
 135 individual block partitions
 136 .\".SH SEE ALSO
 137 .\".BR scsi (4)