1SD(4)                      Linux Programmer's Manual                     SD(4)
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NAME

6       sd - driver for SCSI disk drives
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SYNOPSIS

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

13       The block device name has the following form: sdlp, where l is a letter
14       denoting the physical drive, and p is a number denoting  the  partition
15       on  that  physical drive.  Often, the partition number, p, will be left
16       off when the device corresponds to the whole drive.
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18       SCSI disks have a major device number of 8, and a minor  device  number
19       of  the form (16 * drive_number) + partition_number, where drive_number
20       is the number of the physical drive in order of detection,  and  parti‐
21       tion_number is as follows:
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23       +3     partition 0 is the whole drive
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25              partitions 1–4 are the DOS "primary" partitions
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27              partitions 5–8 are the DOS "extended" (or "logical") partitions
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29       For example, /dev/sda will have major 8, minor 0, and will refer to all
30       of the first SCSI drive in the system; and /dev/sdb3 will have major 8,
31       minor  19,  and  will refer to the third DOS "primary" partition on the
32       second SCSI drive in the system.
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34       At this time, only block devices are provided.  Raw  devices  have  not
35       yet been implemented.
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DESCRIPTION

38       The following ioctls are provided:
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40       HDIO_GETGEO
41              Returns the BIOS disk parameters in the following structure:
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43           struct hd_geometry {
44               unsigned char  heads;
45               unsigned char  sectors;
46               unsigned short cylinders;
47               unsigned long  start;
48           };
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50              A pointer to this structure is passed as the ioctl(2) parameter.
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52              The  information  returned in the parameter is the disk geometry
53              of the drive as understood by DOS!  This  geometry  is  not  the
54              physical  geometry  of  the drive.  It is used when constructing
55              the drive's partition table, however, and is needed  for  conve‐
56              nient operation of fdisk(1), efdisk(1), and lilo(1).  If the ge‐
57              ometry information is not available, zero will be  returned  for
58              all of the parameters.
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60       BLKGETSIZE
61              Returns  the  device  size  in  sectors.  The ioctl(2) parameter
62              should be a pointer to a long.
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64       BLKRRPART
65              Forces a reread of the SCSI disk partition tables.  No parameter
66              is needed.
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68              The  SCSI  ioctl(2)  operations  are  also  supported.   If  the
69              ioctl(2) parameter is required, and it is  NULL,  then  ioctl(2)
70              fails with the error EINVAL.
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FILES

73       /dev/sd[a-h]
74              the whole device
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76       /dev/sd[a-h][0-8]
77              individual block partitions
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COLOPHON

80       This  page  is  part of release 5.13 of the Linux man-pages project.  A
81       description of the project, information about reporting bugs,  and  the
82       latest     version     of     this    page,    can    be    found    at
83       https://www.kernel.org/doc/man-pages/.
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87Linux                             2017-09-15                             SD(4)
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