sd(4) Kernel Interfaces 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:
• 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
Linux man-pages 6.7 2023-10-31 sd(4)
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