Manual browser: dkctl(8)

DKCTL(8) System Manager's Manual DKCTL(8)


dkctlprogram to manipulate disks


dkctl device

dkctl device command [arg [...]]


dkctl allows a user or system administrator to manipulate and configure disks in various ways. It is used by specifying a disk to manipulate, the command to perform, and any arguments the command may require. device is the disk (wdN, sdN, ...) containing the wedges unless noted otherwise. If dkctl is called without any command, it displays strategy, cache, and all of the wedges of the specified device.


The following commands are supported:
Get and display the cache enables for the specified device.
setcache none | r | w | rw [save]
Set the cache enables for the specified device. The enables are as follows:
Disable all caches on the disk.
Enable the read cache, and disable all other caches on the disk.
Enable the write cache, and disable all other caches on the disk.
Enable both the read and write caches on the disk.
If specified, and the cache enables are savable, saves the cache enables in the disk's non-volatile parameter storage.
synccache [force]
Causes the cache on the disk to be synchronized, flushing all dirty write cache blocks to the media. If force is specified, the cache synchronization command will be issued even if the kernel does not believe that there are any dirty cache blocks in the disk's cache.
keeplabel [yes | no]
Specify to keep or drop the in-core disklabel on the last close of the disk device. (Keep if yes is specified, drop if no is specified.)
badsector flush | list | retry
Used for managing the kernel's bad sector list for wd(4) devices. The software bad sector list is only maintained if the option “WD_SOFTBADSECT” was specified on kernel configuration.
Clears the in kernel list of bad sectors.
Prints out the list of bad sector ranges recorded by the kernel.
Flushes the in kernel list and then retries all of the previously recorded bad sectors, causing the list to self update. This option can only be used with character devices.
addwedge name startblk blkcnt ptype
Define a “wedge” on the specified disk starting at block number startblk and spanning blkcnt blocks. You need to create the partition first with fdisk(8) or gpt(8), dkctl will just name it. The wedge will have the volume name name and the partition type ptype. Valid choices for ptype would be unused, swap, ffs, lfs, ext2fs, cd9660, ados, hfs, msdos, filecore, raidframe, ccd, appleufs, ntfs, and cgd.

The device name of the virtual block device assigned to the wedge will be displayed after the wedge has been successfully created. See dk(4) for more information about disk wedges.

delwedge dk
Delete the wedge specified by its device name dk from the specified disk.
Display information about the specified disk wedge. device in this case is the wedge name.
List all of the wedges configured on the specified disk.
Delete all wedges configured on the specified disk, and autodiscover the wedges again. Wedges that are in use are not deleted and conflicting or overlapping wedges are not created. You need to list wedges to find out what has changed.
strategy [name]
Get and set the disk I/O scheduler (buffer queue strategy) on the drive. If you do not provide a name argument, the currently selected strategy will be shown. To set the bufq strategy, the name argument must be specified. name must be the name of one of the built-in kernel disk I/O schedulers. To get the list of supported schedulers, use the following command:

$ sysctl kern.bufq.strategies

Note: The addwedge and delwedge commands only modify the in-kernel representation of disks; for modifying information on the disks themselves, refer to fdisk(8) or gpt(8).


The dkctl command first appeared in NetBSD 1.6.


The dkctl command was written by Jason R. Thorpe of Wasabi Systems, Inc.
November 4, 2014 NetBSD 7.0