ArGest Backup User Guide

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  5. The Syntax of brutab Entries

The Syntax of brutab Entries

Device entries in brutab consist of multiple fields separated by white space (spaces or tabs) or a new line character. Entries may span more than one line if you enter your shell’s escape character (usually a \) immediately before the newline character at the end of the line.

Each brutab entry begins with the device name, followed by one or more parameter fields. All tabs and blanks between fields are ignored. Any line that begins with a # character is ignored and will be treated as a comment (except for global brutab parameter lines, which are described later).

The device name has the following form:

device name | ... | device name

For example:

ntape0
or
ntape0|ntape1|ntape2…

If the device name field specifies multiple devices, each device must have exactly the same characteristics and capabilities. Note the lack of spaces in the device name field.

There are two types of parameter fields used to define the characteristics of a backup device. Fields are either Alphanumeric or Boolean (true/false). An alphanumeric field consists of the parameter name, followed immediately by an equal sign ‘=’ and the value. There must not be any spaces before or after the equal sign. The value following the equal sign may be a number, a symbolic value, or a string. String values must be enclosed in double quotes.

A Boolean field consists of the parameter name only. If the field is present, the corresponding device capability will be enabled (turned ON). If the Boolean field is absent, the corresponding device capability will be disabled (turned OFF).

Here is an example of various parameters and values:

size=640K noautoscan pwerr=EIO \
fmtcmd=”format /dev/rfd1135ds9”

NOTE: That there is no space between the parameter name and the value. Numeric values may be given in absolute form or appended with a scale factor of:

b or B Blocks (2048 bytes)
k or K Kilobytes (1024 bytes)
m or M Megabytes (1024*1024 bytes)
g or G Gigabytes (1024*1024*1024 bytes)

The letter T may also be used as a modifier after the scale factors M or G. This is commonly used when specifying tape size.

When T is specified, a multiplier of 1000 will be used (instead of 1024). This is useful when using the tape size given by the tape manufacturer. Tape megabytes are measured differently than memory megabytes. A tape that is specified as 150 tape megabytes will actually hold only 143 memory megabytes.

Listed below are the scale factors when the T (for Tape) modifier is used:

kt or KT Kilobytes (1000 bytes)
mt or MT Megabytes (1000*1000 bytes)
gt or GT Gigabytes (1000*1000*1000 bytes)

This is an example of how to specify the media size for a tape with a manufacturer-specified size of 525 megabytes:

size=525MT

Certain parameter fields (like pwerr=EIO) refer to error codes returned by the UNIX systems. The values for these parameters may be given as digits or in symbolic form (like EIO or ENOSPC).

NOTE FOR PROGRAMMERS: Symbolic error codes are usually defined in the development system header include file /usr/include/errno.h.