Logical Device Names

The logical device name is created by the operating system when the peripheral is first installed and booted with the reconfiguration option. Logical device names are located in the /dev directory. A logical device name is a file that is symbolically linked to the physical device name (names in the /devices directory). The file name reflects the address and physical connection of the device to the system. The logical device name is the address that you use when you work with the device.

Logical device names for a disk drives are created as follows:

/dev/[r]dsk/cntndnsn

• cn - is the controller (or interface) number such as c0, c1, c2, and so on. Controller numbers are logically assigned in sequential order. c0 often represents a built-in SCSI controller.

• tn - is the target ID of the device such as t0, t1, t2, t3 and so on.

• dn - is the device number (often called a LUN). It reflects the actual address of the device unit. This is usually d0 for most SCSI disks because there is only one disk attached to the target controller (device interface).

• sn - is the slice number that represents a partition, or slice, of a disk. Valid numbers are 0 through 7.

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Note -

Do not apply the above explanation to disks that are part of a SPARCstorage Array (a device connected to a SOC card). Disks in a SPARCstorage Array have logical device names with the same /dev/[r]dsk/cntndnsn; however, they are interpreted differently.

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Logical device names for disk drives are created in two subdirectories in the /dev directory; rdsk and dsk. As you use disk logical device names with various commands you must use the appropriate one from either /dev/rdsk or /dev/dsk depending on whether the command uses a raw (or character) device interface, or a block device interface. The distinction is made based on how data is read from the device:

• Raw device interface - A raw device transfers data character by character in just the exact amount of data needed for a given task. Use the logical device name from the /dev/rdsk directory.

• Block device interface - A block device transfers data in a predetermined amount, often from a buffer from which large blocks of data are read at once. Use the logical device name from the /dev/dsk directory

In general, there are three commands that require a block device: mount, umount, and df. Most other commands function best when you use the raw device. When you're not sure whether a command requires use of /dev/dsk or /dev/rdsk, check the man page for that command.

CD-ROM logical device names are created following the same scheme as disk drives (see above). The following is an example of a CD-ROM logical device name:

/dev/rdsk/cnt6dnsn

SCSI tape logical device name example:

/dev/rmt/0

Table A-2 Tape Drive Logical Device Names

Tape Drive	Target ID	Primary Logical Device Name	Additional Logical Device Names
First tape drive	4	/dev/rmt/0	/dev/rmt/0n    /dev/rmt/0h    /dev/rmt/0c    /dev/rmt/0ubn
Second tape drive	5	/dev/rmt/1	/dev/rmt/1n    /dev/rmt/1h    /dev/rmt/1c    /dev/rmt/1ubn

For most tape operations you should use the primary logical device name because the tape drive will use its optimum default characteristics. However, if you desire to specify a particular tape drive behavior, append a letter (up to three letters) to the appropriate logical device name as follows:

• Append a letter to the drive number to specify a tape density where h is high, m is medium, l is low, c is compressed, and u is ultra. Not all tape drives support all densities. If you are in doubt, do not specify a density. The tape drive should default to the optimum setting.

  Append a b to the drive number to specify BSD behavior. This means that when reading past an end-of-file mark, it returns the first record of the next file. This is desirable if the tape is going to be read on a BSD UNIX system.

  Append an n to the drive number to specify no rewind operation, otherwise the tape will rewind when the tape operation is complete.

Valid tape name combinations are shown in the table below. If you are working with the second tape drive use a 1 instead of 0.

0n   0b 0bn

0c   0cb   0cbn   0cn

0h 0hb 0hbn 0hbn

0m   0mb   0mbn 0mn

0l   0lb   0lbn   0ln

0u   0ub   0ubn   0un