SD(4) BSD Kernel Interfaces Manual SD(4)
sd -- SCSI disk driver
sd* at scsibus?
#sd0 at scsibus0 target 3 lun 0 (fixed-configuration example)
The sd driver provides support for a SCSI disk. It allows the disk to be
divided up into a set of pseudo devices called partitions. In general
the interfaces are similar to those described by wd(4).
SCSI devices have a fairly high level interface to the system and talk to
it via a SCSI host adapter (e.g., ahc(4)). A SCSI adapter must also be
separately configured into the system before a SCSI disk can be config-
When the SCSI adapter is probed during boot, the SCSI bus is scanned for
devices. Any devices found which answer as 'Direct' type devices will be
attached to the sd driver.
On many systems disklabel(8) is used to partition the drive into filesys-
tems. On some systems the OpenBSD portion of the disk resides within a
native partition, and another program is used to create the OpenBSD por-
For example, the i386 port uses fdisk(8) to partition the disk into a
BIOS level partition. This allows sharing the disk with other operating
The following ioctl(2) calls apply to SCSI disks as well as to other
disks. They are defined in the header file <sys/dkio.h>.
DIOCGDINFO struct disklabel *
Read, from the kernel, the in-core copy of the disklabel for the
drive. This may be a fictitious disklabel if the drive has never
been initialized, in which case it will contain information read
from the SCSI inquiry commands.
DIOCSDINFO struct disklabel *
Give the driver a new disklabel to use. The driver will not
write the new disklabel to the disk.
DIOCWDINFO struct disklabel *
Give the driver a new disklabel to use. The driver will write
the new disklabel to the disk.
DIOCLOCK int *
Lock the media cartridge into the device, or unlock a cartridge
previously locked. Used to prevent user and software eject while
the media is in use.
Eject the media cartridge from a removable device.
DIOCINQ struct dk_inquiry *
Read the devices product information.
In addition, the scsi(4) general ioctl() commands may be used with the sd
driver, but only against the 'c' (whole disk) partition.
If a removable device is attached to the sd driver, then the act of
changing the media will invalidate the disklabel and information held
within the kernel. To avoid corruption, all access to the device will be
discarded until there are no more open file descriptors referencing the
device. During this period, all new open attempts will be rejected.
When no more open file descriptors reference the device, the first next
open will load a new set of parameters (including disklabel) for the
/dev/sdup block mode SCSI disk unit u, partition p
/dev/rsdup raw mode SCSI disk unit u, partition p
intro(4), scsi(4), wd(4), disklabel(5), disklabel(8), fdisk(8)
The sd driver was originally written for Mach 2.5, and was ported to
FreeBSD by Julian Elischer. It was later ported to OpenBSD.
BSD July 2, 2014 BSD