freebsd man page for rdump

DUMP(8) 						    BSD System Manager's Manual 						   DUMP(8)

NAME
     dump, rdump -- file system backup

SYNOPSIS
     dump [-0123456789acLnrRSu] [-B records] [-b blocksize] [-C cachesize] [-D dumpdates] [-d density] [-f file | -P pipecommand] [-h level]
	  [-s feet] [-T date] filesystem
     dump -W | -w

DESCRIPTION
     The dump utility examines files on a file system and determines which files need to be backed up.	These files are copied to the given disk,
     tape or other storage medium for safe keeping (see the -f option below for doing remote backups).	A dump that is larger than the output
     medium is broken into multiple volumes.  On most media the size is determined by writing until an end-of-media indication is returned.  This
     can be enforced by using the -a option.

     On media that cannot reliably return an end-of-media indication (such as some cartridge tape drives) each volume is of a fixed size; the
     actual size is determined by the tape size and density and/or -B options.	By default, the same output file name is used for each volume
     after prompting the operator to change media.

     The file system to be dumped is specified by the argument filesystem as either its device-special file or its mount point (if that is in a
     standard entry in /etc/fstab).

     dump may also be invoked as rdump.  The 4.3BSD option syntax is implemented for backward compatibility, but is not documented here.

     The following options are supported by dump:

     -0-9    Dump levels.  A level 0, full backup, guarantees the entire file system is copied (but see also the -h option below).  A level number
	     above 0, incremental backup, tells dump to copy all files new or modified since the last dump of any lower level.	The default level
	     is 0.

     -a      ``auto-size''.  Bypass all tape length considerations, and enforce writing until an end-of-media indication is returned.  This fits
	     best for most modern tape drives.	Use of this option is particularly recommended when appending to an existing tape, or using a tape
	     drive with hardware compression (where you can never be sure about the compression ratio).

     -B records
	     The number of kiloby