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SD(4)                        Device Drivers Manual                       SD(4)

     sd - SCSI and ATAPI disk driver

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

     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

     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).

     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 operating

     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 milliseconds).  This is used to set watchdog timers
                    in the SCSI HBA driver to catch commands that might have
                    died on the device.

     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> and use data
     structures defined in <sys/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.

     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 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


     ioctl(2), 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 NetBSD.

NetBSD 10.99                     June 9, 2016                     NetBSD 10.99