Specifying the -R option tells BRU to exclude all files on remote systems. It lets you back up files on your local system and not reach out across the network to other systems. The following example backs up only files on the local system:
bru -cv -R /
For an individual machine that has remote connections and mounted filesystems from remote machines, archiving files from the remote machines could mean generating a very large archive. The -R option should be used to limit the backup to your local files.