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Device special files tell the operating system which device
driver to use, how to find the peripheral device, and what characteristics
the peripheral device should employ. Characteristics vary by device.
Thus, device special files for magneto-optical devices show the
surface being addressed, while those for tape drives show rewind
and density. Most device special file names contain the location of the
device on the bus architecture. To see this, display the files in
any subdirectory of the /dev directory. Note, all mass storage devices adhere
to a syntax that includes c#t#d#[s#] (other kinds of device files use a related convention): Title not available (Understanding Device Special File Names ) - c#
represents the card instance number
for the class of interface card to which the
device is connected. Classes of interface cards include ext_bus, graphics, tty, lan, and others. The card instance of an interface
card is unique for its specific class. There is no relationship between
the instance number and the slot number of the interface card in
the card cage. Class and instance number can be seen in the first two columns
of /usr/sbin/ioscan -f output. When interpreting a device special file, the only significant
instance number is the card instance (that is, the instance number
for the class of interface to which a device
is attached). Thus, in a sample disk device file /dev/rdsk/c1t4d0, the c1 refers to the card instance, not to
an LU number (as in previous releases). - t#
represents the target address of
the device on the interface bus, and can range from 0 to 7 maximum. Typically t# is the address set with jumpers or dip switches
on the device itself. - d#
represents the device number,
and can range from 0 to 7 maximum. On SCSI devices, d# is the SCSI LUN; on HP-FL and HP-IB, it is the unit
number. Except for multi-function devices, d# is typically d0. - s#
specifies section number
(optional; made available for backward compatibility). Note, section 0 now represents the entire disk,
while section 2 represents a small disk section (previously section 0). If the s# is not shown, the device special file refers to
the entire disk.
Sample
Device Special File Names | |
Every peripheral-specific chapter in this book has tables
of configuration requirements that show the default device special
file names for that class of device. Here are some sample device
special files and their possible meanings: - /dev/rdsk/c0t6d0
Entire disk accessed in character (raw) mode through SCSI card instance 0, target 6,
LUN 0. - /dev/dsk/c3t2d4
Entire disk accessed in block mode through HP-FL card
instance 3, address 2, Unit 4. - /dev/rac/c0t0d0_11a
Surface 11a of a magneto-optical disk whose autochanger
in a disk library accessed in raw mode through card instance 0,
target 0, LUN 0. - /dev/rmt/c1t0d0BESTnb
Tape drive accessed through card instance 1, target 0,
LUN 0. Tape writes at best available density/format, no rewind,
Berkeley-style close. - /dev/rmt/0mnb
Tape drive device special file with identical characteristics
(linked) to /dev/rmt/c1t0d0BESTnb. - /dev/floppy/c1t3d0
Entire floppy disk drive accessed in block mode through
SCSI card instance 1 located in slot 13, with target 3, LUN 0. - /dev/tty0p0
Serial port of built-in card instance 0 port 0, hardwired
at address 56.0; accessed through driver mux4. - /dev/c1t0d0_lp
Parallel port on core I/O card 1, set to handshake mode
2. - /dev/lp
Parallel port on core I/O card 1, set to handshake mode
2; device file is linked to /dev/c1t0d0_lp.
Both lssf and ioscan commands display the interface to which a device
is connected. These are discussed in the next sections. |
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