devtable - Device descriptor table for use with tape functions

DESCRIPTION

devtable is an ASCII file in the pass directory, $PASSDIR, that provides information about the devices available for various tape operations. This data is used by archive, and most telemetry ingesters that read from tape.

The basic record format for the devtable is:

tape-path generic-name block-size flags

The following is a sample record, defining characteristics of an HP DAT with an APUNIX driver, in streaming 1024-byte block mode:

/dev/ncht0 ht0 1024 SHREC

The first three fields are required. The generic-name must be a substring of the tape-path. The block-size should be 1024 for fixed block tapes; block-size is ignored for variable block tapes.

The following flags are supported; they must be capitalized:

SHREC - Device with fixed size blocks (like 1/4" tape)

STREAD - Read record never goes beyond tape end-of-file

STSKIP - Skip record never goes beyond tape end-of-file

IGNPEOF - Same as STREAD and STSKIP together

BYEOM - When at end-of-media, read goes past 2nd EOF

NOEOM - Does not support (reliable) end-of-media command

DEADEND - Cannot use empty read to test end-of-media (HP 8mm)

SOFTBOT - Backspace file beyond beginning-of-media is not detectable using error status or file counts

BADFSR - Multiple record skip doesn't see EOF's

NOTRL - Do not write trailer file at end of tape

REWRT - If not at end-of-media, cannot write data without first writing an EOF (an 8mm problem!)

NOMTGET - Do not attempt to get tape status in order to double check success of tape skip operations (an IRIX 6.2 problem!)

 

Devices found in this table are assumed to be tape devices and to support tape ioctl() related calls.

Devices in this table are normally all no-rewind devices, although this is not a requirement.

Tape devices not found in this table are assumed to have no flags; e.g., variable blocking, records reads and skips will go past EOF's, reliable end-of-media instruction, best to write trailers, OK to get tape status to double check success of skip operations.

Last Update: $Date: 2000/07/21 21:30:00 $