dparam, dkinit -- display or change hard disk characteristics


/bin/dparam -w [ disk_node ]
/bin/dparam disk_node [ cylinders heads wrt_reduce precomp ecc control landzone sectors ]

/etc/dkinit /dev/rhd00
/etc/dkinit [ drive controller_number controller_type ]


The dparam command displays or changes the hard disk characteristics currently in effect on the disk referred to by the raw device disk_node. Any changes take effect immediately and are also written to the masterboot block for subsequent boots. If you are using a non-standard hard disk, run dparam before accessing the drive.

The default disk_node accessed by dparam is the raw device for the entire primary hard disk (/dev/rhd00).

dparam takes one option:

Copies /etc/masterboot to the disk's masterboot block to ensure that non-standard hard disks are supported for the specified drive. This must precede any call to write non-standard disk parameters so that these are saved correctly in the masterboot block.
When writing characteristics for the specified hard disk, dparam changes the current disk controller status and updates the masterboot block. You must specify all the following hard disk characteristics:

number of cylinders

number of heads

cylinder number at which to start reducing the current when writing

cylinder number at which to start precompensation when writing

number of bits of error correction on I/O transfers

controller type number

cylinder number used to park the heads on shutting down the system (landing zone)

number of sectors per track
The parameters are specific to the type of hard disk; consult the hardware specification manual or the manufacturer for the correct information.

dkinit provides a menu-driven front end to dparam. For more details on the use of dkinit, please refer to ``Changing default disk parameters using dkinit'' in the SCO OpenServer Handbook.

Invoke dkinit with /dev/rhd00 as its argument if the primary hard disk is to be examined. To specify a different drive, supply the following three arguments:

the number of the drive on a given controller; 0 or 1

the number of the controller of a given type; 0 to 6

the controller type:

OMTI disk controller

IDA disk controller

IDE, ST506 or ESDI disk controller
When installing a hard disk using mkdev hd, dkinit is invoked only for IDE, ST506, IDA, and ESDI controllers. dparam -w is run silently to write the masterboot block to SCSI and OMTI disks.


Run dparam on the root hard disk and copy /etc/masterboot to it:

/bin/dparam -w

Run dparam on the secondary hard disk:

/bin/dparam /dev/rhd10

Re-specify the hard disk characteristics of the root hard disk:

/bin/dparam /dev/rhd00 700 4 256 180 5 0 640 17


Never run dparam on a disk partition or division. If specified, disk_node must be a raw device that refers to a whole disk.


This utility changes the kernel's view of the hard disk parameters. It may be subject to restrictions imposed by the hardware configuration.

The masterboot file is usually copied to drive 0's masterboot. Drive 1's masterboot is only used to determine virtual drive partitioning, not for masterboot code to boot up or for disk parameters. Disk parameters for both drives are kept on disk 0.

dparam copies /etc/masterboot to sector 3 (1-based) on some devices (such as Enhanced Memory Adapters). This is to prevent it overwriting the POSTEXT masterboot sector that configures the card at boot time.



raw interface to entire primary hard disk


raw interface to entire secondary hard disk

masterboot block code

information about the hard disks configured on the system

See also

hd(HW), mkdev(ADM)

Standards conformance

dparam and dkinit are not part of any currently supported standard; they are an extension of AT&T System V provided by The Santa Cruz Operation, Inc.
© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003