SD(4) | Device Drivers Manual | SD(4)

# NAME

`sd` — SCSI disk driver

# SYNOPSIS

`sd* at scsibus?`
`#sd0 at scsibus0 target 3 lun 0` (fixed-configuration example)

# DESCRIPTION

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 configured.

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.

# PARTITIONING

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 systems.

# IOCTLS

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.
`DIOCEJECT`
  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.

# NOTES

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 drive.

# FILES

/dev/sd u p
  block mode SCSI disk unit u, partition p
/dev/rsd u p
  raw mode SCSI disk unit u, partition p

# DIAGNOSTICS

None.

# SEE ALSO

intro(4), scsi(4), wd(4), disklabel(5), disklabel(8), fdisk(8)

# HISTORY

Julian Elischer wrote `sd` for Mach 2.5 and ported it to 386BSD.

December 21, 2024 | Debian