SD(4)                        Device Drivers 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

     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
     filesystems.  On some systems the OpenBSD portion of the disk resides
     within a native partition, and another program is used to create the
     OpenBSD portion.

     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.

OpenBSD 5.9                      July 2, 2014                      OpenBSD 5.9

[Unix Hosting | Open-Source | Contact Us]
[Engineering & Automation | Software Development | Server Applications]