SD(4)							   BSD Kernel Interfaces Manual 						     SD(4)

NAME

     sd -- SCSI and ATAPI disk driver

SYNOPSIS

     sd* at scsibus? target ? lun ?
     sd3 at scsibus0 target 3 lun 0
     sd* at atapibus? drive ? flags 0x0000

DESCRIPTION

     The sd driver provides support for SCSI bus and Advanced Technology Attachment Packet Interface (ATAPI) disks.  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).

     Where the wd(4) device has a fairly low level interface to the system, SCSI devices have a much higher level interface and talk to the system
     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-
     ured.

     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.

     For the use of flags with ATAPI devices, see wd(4).

PARTITIONING

     On many systems disklabel(8) is used to partition the drive into filesystems.  On some systems the NetBSD portion of the disk resides within
     a native partition, and another program is used to create the NetBSD 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 operat-
     ing systems.

CONFIGURATION OPTIONS

     The following config(1) options may be applied to SCSI disks as well as to other disks.

     SDRETRIES	    Set the number of retries that will be performed for operations it makes sense to retry (e.g., normal reads and writes). The
		    default is four (4).

     SD_IO_TIMEOUT  Set amount of time, in milliseconds, a normal read or write is expected to take. The defaults is sixty seconds (60000 mil-
		    liseconds). This is used to set watchdog timers in the SCSI HBA driver to catch commands that might have died on the device.

IOCTLS

     The following ioctl(2) calls apply to SCSI disks as well as to other disks.  They are defined in the header file <disklabel.h>.

     DIOCGDINFO  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  Give the driver a new disklabel to use.  The driver will not write the new disklabel to the disk.

     DIOCKLABEL  Keep or drop the in-core disklabel on the last close.

     DIOCWLABEL  Enable or disable the driver's software write protect of the disklabel on the disk.

     DIOCWDINFO  Give the driver a new disklabel to use.  The driver will write the new disklabel to the disk.

     DIOCLOCK	 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.

     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 accesses to the device will be discarded until there are no more open file descriptors referenc-
     ing 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/sdup	    block mode SCSI disk unit u, partition p
     /dev/rsdup     raw mode SCSI disk unit u, partition p

DIAGNOSTICS

     None.

SEE ALSO

     ioctl(2), intro(4), scsi(4), wd(4), disklabel(5), disklabel(8), fdisk(8), scsictl(8)

HISTORY

     The sd driver was originally written for Mach 2.5, and was ported to FreeBSD by Julian Elischer.  It was later ported to NetBSD.

BSD
								 January 18, 1996							       BSD