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man pages section 1M: System Administration Commands

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Updated: July 2017



disks - creates /dev entries for hard disks attached to the system


/usr/sbin/disks [-C] [-r rootdir]


devfsadm(1M) is now the preferred command for /dev and should be used instead of disks.

disks creates symbolic links in the /dev/dsk and /dev/rdsk directories pointing to the actual disk device special files under the /devices directory tree. It performs the following steps:

  1. disks searches the kernel device tree to see what hard disks are attached to the system. It notes the /devices pathnames for the slices on the drive and determines the physical component of the corresponding /dev/dsk or /dev/rdsk name.

  2. The /dev/dsk and /dev/rdsk directories are checked for disk entries − that is, symbolic links with names of the form cN[tN]d NsN, or cN[tN]dNpN, where N represents a decimal number. cN is the logical controller number, an arbitrary number assigned by this program to designate a particular disk controller. The first controller found on the first occasion this program is run on a system, is assigned number 0. t N is the bus-address number of a subsidiary controller attached to a peripheral bus such as SCSI or IPI (the target number for SCSI, and the facility number for IPI controllers). dN is the number of the disk attached to the controller. sN is the slice number on the disk. pN is the FDISK partition number used by fdisk(1M). (x86 Only)

  3. If only some of the disk entries are found in /dev/dsk for a disk that has been found under the /devices directory tree, disks creates the missing symbolic links. If none of the entries for a particular disk are found in /dev/dsk, disks checks to see if any entries exist for other disks attached to the same controller, and if so, creates new entries using the same controller number as used for other disks on the same controller. If no other /dev/dsk entries are found for slices of disks belonging to the same physical controller as the current disk, disks assigns the lowest-unused controller number and creates entries for the disk slices using this newly-assigned controller number.

disks is run automatically each time a reconfiguration-boot is performed or when add_drv(1M) is executed. When invoking disks manually, first run drvconfig(1M) to ensure /devices is consistent with the current device configuration.

Notice to Driver Writers

disks considers all devices with a node type of DDI_NT_BLOCK, DDI_NT_BLOCK_CHAN, DDI_NT_CD, DDI_NT_BLOCK_WWN or DDI_NT_CD_CHAN to be disk devices. disks requires the minor name of disk devices obey the following format conventions.

The minor name for block interfaces consists of a single lowercase ASCII character, a through u, representing the slices and the primary partitions. The minor name for logical drive block interfaces consists of the strings p5 through p36. The minor name for character (raw) interfaces consists of a single lowercase ASCII character, a through a, followed by the string ,raw, representing the slices and the primary partitions. The minor name for logical drive character (raw) interfaces consists of the string p5 through p36 followed by ,raw.

disks performs the following translations:

  • a through p to s0 through s15

  • q through u to p0 through p4

  • p5 through p36 to p5 through p36

SPARC drivers should only use the first eight slices: a through h, while x86 drivers can use a through u, with q through u corresponding to fdisk(1M) primary partitions. q represents the entire disk, while r, s, t, and u represent up to four additional primary partitions. For logical drives, p5 to p36 correspond to the 32 logical drives that are supported. The device nodes for logical drives change dynamically as and when they are created or deleted.

To prevent disks from attempting to automatically generate links for a device, drivers must specify a private node type and refrain from using a node type: DDI_NT_BLOCK, DDI_NT_BLOCK_CHAN, DDI_NT_CD, or DDI_NT_CD_CHAN when calling ddi_create_minor_node(9F).


The following options are supported:


Causes disks to remove any invalid links after adding any new entries to /dev/dsk and /dev/rdsk. Invalid links are links which refer to non-existent disk nodes that have been removed, powered off, or are otherwise inaccessible.

–r rootdir

Causes disks to presume that the /dev/dsk, /dev/rdsk and /devices directory trees are found under rootdir, not directly under /.


If disks finds entries of a particular logical controller linked to different physical controllers, it prints an error message and exits without making any changes to the /dev directory, since it cannot determine which of the two alternative logical-to-physical mappings is correct. The links should be manually corrected or removed before another reconfiguration-boot is performed.


Example 1 Creating Block and Character Minor Devices

The following example demonstrates creating the block and character minor devices from within the xkdisk driver's attach(9E) function.

#include    <sys/dkio.h>
 * Create the minor number by combining the instance number
 * with the slice number.
#define MINOR_NUM(i, s)   ((i) << 4 | (s))

xkdiskattach(dev_info_t *dip, ddi_attach_cmd_t cmd)
    int instance, slice;
    char name[8];

        /* other stuff in attach... */

    instance = ddi_get_instance(dip);
    for (slice = 0; slice < V_NUMPAR; slice++) {
         * create block device interface
        sprintf(name, "%c", slice + 'a');
        ddi_create_minor_node(dip, name, S_IFBLK,
            MINOR_NUM(instance, slice), DDI_NT_BLOCK_CHAN, 0);

         * create the raw (character) device interface
        sprintf(name,"%c,raw", slice + 'a');
        ddi_create_minor_node(dip, name, S_IFCHR,
            MINOR_NUM(instance, slice), DDI_NT_BLOCK_CHAN, 0);

Installing the xkdisk disk driver on a Sun Fire 4800, with the driver controlling a SCSI disk (target 3 attached to an isp(7D) SCSI HBA) and performing a reconfiguration-boot (causing disks to be run) creates the following special files in /devices.

# ls -l /devices/ssm@0,0/pci@18,700000/pci@1/SUNW,isptwo@4/
brw-r-----   1 root sys   32, 16 Aug 29 00:02 xkdisk@3,0:a
crw-r-----   1 root sys   32, 16 Aug 29 00:02 xkdisk@3,0:a,raw
brw-r-----   1 root sys   32, 17 Aug 29 00:02 xkdisk@3,0:b
crw-r-----   1 root sys   32, 17 Aug 29 00:02 xkdisk@3,0:b,raw
brw-r-----   1 root sys   32, 18 Aug 29 00:02 xkdisk@3,0:c
crw-r-----   1 root sys   32, 18 Aug 29 00:02 xkdisk@3,0:c,raw
brw-r-----   1 root sys   32, 19 Aug 29 00:02 xkdisk@3,0:d
crw-r-----   1 root sys   32, 19 Aug 29 00:02 xkdisk@3,0:d,raw
brw-r-----   1 root sys   32, 20 Aug 29 00:02 xkdisk@3,0:e
crw-r-----   1 root sys   32, 20 Aug 29 00:02 xkdisk@3,0:e,raw
brw-r-----   1 root sys   32, 21 Aug 29 00:02 xkdisk@3,0:f
crw-r-----   1 root sys   32, 21 Aug 29 00:02 xkdisk@3,0:f,raw
brw-r-----   1 root sys   32, 22 Aug 29 00:02 xkdisk@3,0:g
crw-r-----   1 root sys   32, 22 Aug 29 00:02 xkdisk@3,0:g,raw
brw-r-----   1 root sys   32, 23 Aug 29 00:02 xkdisk@3,0:h
crw-r-----   1 root sys   32, 23 Aug 29 00:02 xkdisk@3,0:h,raw

/dev/dsk will contain the disk entries to the block device nodes in /devices

# ls -l /dev/dsk
/dev/dsk/c0t3d0s0 -> ../../devices/[...]/xkdisk@3,0:a
/dev/dsk/c0t3d0s1 -> ../../devices/[...]/xkdisk@3,0:b
/dev/dsk/c0t3d0s2 -> ../../devices/[...]/xkdisk@3,0:c
/dev/dsk/c0t3d0s3 -> ../../devices/[...]/xkdisk@3,0:d
/dev/dsk/c0t3d0s4 -> ../../devices/[...]/xkdisk@3,0:e
/dev/dsk/c0t3d0s5 -> ../../devices/[...]/xkdisk@3,0:f
/dev/dsk/c0t3d0s6 -> ../../devices/[...]/xkdisk@3,0:g
/dev/dsk/c0t3d0s7 -> ../../devices/[...]/xkdisk@3,0:h

and /dev/rdsk will contain the disk entries for the character device nodes in /devices

# ls -l /dev/rdsk
/dev/rdsk/c0t3d0s0 -> ../../devices/[...]/xkdisk@3,0:a,raw
/dev/rdsk/c0t3d0s1 -> ../../devices/[...]/xkdisk@3,0:b,raw
/dev/rdsk/c0t3d0s2 -> ../../devices/[...]/xkdisk@3,0:c,raw
/dev/rdsk/c0t3d0s3 -> ../../devices/[...]/xkdisk@3,0:d,raw
/dev/rdsk/c0t3d0s4 -> ../../devices/[...]/xkdisk@3,0:e,raw
/dev/rdsk/c0t3d0s5 -> ../../devices/[...]/xkdisk@3,0:f,raw
/dev/rdsk/c0t3d0s6 -> ../../devices/[...]/xkdisk@3,0:g,raw
/dev/rdsk/c0t3d0s7 -> ../../devices/[...]/xkdisk@3,0:h,raw



Disk entries (block device interface)


Disk entries (character device interface)


Device special files (minor device nodes)


See attributes(5) for descriptions of the following attributes:


See Also

add_drv(1M), devfsadm(1M), fdisk(1M), attributes(5), isp(7D), devfs(7FS), dkio(7I), attach(9E), ddi_create_minor_node(9F)

Writing Device Drivers for Oracle Solaris 11.3


disks silently ignores malformed minor device names.