HP-UX System Administrator's Guide: Overview

The first two items in the list above are determined by the major number of a device
special file, the latter two items are determined by the minor number of a device special
file.
The Anatomy of a Device Special File
Device Special Files (DSFs) are comprised of the following parts:
file name
This is the name of the file that appears in the /dev directory tree
major number A number used to identify which driver to use to communicate
with the device/LUN associated with that device special file
The major number is an index for the device driver into one of two
kernel tables — bdevsw, the block device switch table and cdevsw,
the character device switch table.
Drivers that support both block and character I/O (such as SCSI
disk driver and optical autochanger) have both a block major
number and a character major number. Devices that support only
character-mode access have only a character major number.
minor number A number that identifies the hardware location and sometimes
driver-dependent characteristics (usually organized by bit
assignments).
The three parts of a device file can be viewed using the ll (ls -l) command. For
example:
Figure 3-3 Device Special File Components
$ ll /dev/dsk /dev/rdsk /dev/disk /dev/rdisk
/dev/disk:
total 0
brw-r----- 1 bin sys 1 0x000000 Aug 10 16:26 disk2
brw-r----- 1 bin sys 1 0x000001 Aug 10 16:26 disk3
brw-r----- 1 bin sys 1 0x000002 Sep 20 17:27 disk4
brw-r----- 1 bin sys 1 0x000003 Sep 20 17:27 disk5
/dev/dsk:
total 0
brw-r----- 1 bin sys 31 0x006000 Aug 10 16:26 c0t6d0
brw-r----- 1 bin sys 31 0x026000 Aug 10 16:26 c2t6d0
/dev/rdisk:
total 0
crw-r----- 1 bin sys 11 0x000000 Aug 10 16:26 disk2
crw-r----- 1 bin sys 11 0x000001 Sep 20 16:03 disk3
crw-r----- 1 bin sys 11 0x000002 Sep 20 17:27 disk4
crw-r----- 1 bin sys 11 0x000003 Sep 20 17:27 disk5
/dev/rdsk:
total 0
crw-r----- 1 bin sys 188 0x006000 Aug 10 16:26 c0t6d0
crw-r----- 1 bin sys 188 0x026000 Aug 10 16:26 c2t6d0
b = block device special file c= character device special file
File Name
Minor Number
Major Number
You can view, in more human readable form, information contained in the device
special file using the /usr/sbin/lssf command. For example:
# /usr/sbin/lssf /dev/rdsk/*
sdisk card instance 0 SCSI target 6 SCSI LUN 0 section 0 at address 0/0/0/2/0.6.0
Storage on HP-UX 61