BRU 16.0 and later provide a mechanism which allows you to utilize an external compression engine instead of the built in LZO engine. This allows BRU to be used with more modern compression engines as they become available.
To use an external compressor, BRU looks at the global variable “BRUZEXTERN” to determine the program that should be used. You can set this as either an environment variable:
BRUZEXTERN=”/usr/bin/bzip2” ; export BRUZEXTERN
or as a global variable in the
/etc/brutab file (refer to “section 4 – The BRUTAB File” for more information on global variables):
The only requirement is that the compression engine accepts stdin as the compression source and send the resulting compressed data to stdout. Also, you must be able to call the engine for decompression using a -d option to the original program (i.e.: bzip2 -d).
Once a tape is created using an external compressor, you do not need to set the BRUZEXTERN for BRU to be able to extract the compressed archive. The setting for BRUZEXTERN is added to the archive header and future uses of BRU to extract files from this archive will know which program to use for decompression automatically.