Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
DUMP(8)			  BSD System Manager's Manual		       DUMP(8)

     dump, rdump -- file system	backup

     dump [-0123456789aceFinStuX] [-B records] [-b blocksize] [-d density]
	  [-f file] [-h	level] [-k read-blocksize] [-L label] [-l timeout]
	  [-r cachesize] [-s feet] [-T date] [-x snap-backup] files-to-dump
     dump [-W |	-w]

	  (The 4.3BSD option syntax is implemented for backward	compatibility,
	  but is not documented	here).

     dump 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 block count	op-
     tions below.  By default, the same	output file name is used for each vol-
     ume after prompting the operator to change	media.

     files-to-dump is either a single file system, or a	list of	files and di-
     rectories on a single file	system to be backed up as a subset of the file
     system.  In the former case, files-to-dump	may be the device of a file
     system, the path to a currently mounted file system, the path to an un-
     mounted file system listed	in /etc/fstab, or, if -F is given, a file sys-
     tem image.	 In the	latter case, certain restrictions are placed on	the
     backup: -u	is ignored, the	only dump level	that is	supported is -0, and
     all of the	files must reside on the same file system.

     Any files with the	superuser "log"	flag (SF_LOG) set will be skipped.
     These files are assumed to	be wapbl(4) journal files and will not be
     backed up.

     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 a lower level (but see
	     also the -i option	below).	 The default level is 9.

     -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 particu-
	     larly 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 kilobytes per volume, rounded down to a multiple of
	     the blocksize.  This option overrides the calculation of tape
	     size based	on length and density.

     -b	blocksize
	     The number	of kilobytes per dump record.

     -c	     Modify the	calculation of the default density and tape size to be
	     more appropriate for cartridge tapes.

     -d	density
	     Set tape density to density.  The default is 1600 Bits Per	Inch

     -e	     Eject tape	automatically if a tape	change is required.

     -F	     Indicates that files-to-dump is a file system image.

     -f	file
	     Write the backup to file; file may	be a special device file like
	     /dev/rst0 (a tape drive), /dev/rsd1c (a disk drive), an ordinary
	     file, or `-' (the standard	output).  Multiple file	names may be
	     given as a	single argument	separated by commas.  Each file	will
	     be	used for one dump volume in the	order listed; if the dump re-
	     quires more volumes than the number of names given, the last file
	     name will used for	all remaining volumes after prompting for me-
	     dia changes.  If the name of the file is of the form "host:file",
	     or	"user@host:file", dump writes to the named file	on the remote
	     host using	rmt(8).	 Note that methods more	secure than rsh(1)
	     (such as ssh(1)) can be used to invoke rmt(8) on the remote host,
	     via the environment variable RCMD_CMD.  See rcmd(3) for more de-

     -h	level
	     Honor the user "nodump" flag (UF_NODUMP) only for dumps at	or
	     above the given level.  The default honor level is	1, so that in-
	     cremental backups omit such files but full	backups	retain them.

     -i	     The dump is treated as level 9 but	takes into account a previous
	     level 9, if one exists.  This makes it possible to	perform	a
	     "true incremental"	dump.

     -k	read-blocksize
	     The size in kilobyte of the read buffers, rounded up to a multi-
	     ple of the	file system block size.	 Default is 32k.

     -l	timeout
	     If	a tape change is required, eject the tape and wait for the
	     drive to be ready again.  This is to be used with tape changers
	     which automatically load the next tape when the tape is ejected.
	     If	after the timeout (in seconds) the drive is not	ready dump
	     falls back	to the default behavior, and prompts the operator for
	     the next tape.

     -L	label
	     The user-supplied text string label is placed into	the dump
	     header, where tools like restore(8) and file(1) can access	it.
	     Note that this label is limited to	be at most LBLSIZE (currently
	     16) characters, which must	include	the terminating	`\0'.

     -n	     Whenever dump requires operator attention,	notify all operators
	     in	the group "operator" using wall(1).

     -r	cachesize
	     Use that many buffers for read cache operations.  A value of zero
	     disables the read cache altogether, higher	values improve read
	     performance by reading larger data	blocks from the	disk and main-
	     taining them in an	LRU cache.  See	the -k option for the size of
	     the buffers.  Maximum is 512, the size of the cache is limited to
	     15% of the	avail RAM by default.

     -s	feet
	     Attempt to	calculate the amount of	tape needed at a particular
	     density.  If this amount is exceeded, dump	prompts	for a new
	     tape.  It is recommended to be a bit conservative on this option.
	     The default tape length is	2300 feet.

     -S	     Display an	estimate of the	backup size and	the number of tapes
	     required, and exit	without	actually performing the	dump.

     -t	     All informational log messages printed by dump will have the time
	     prepended to them.	 Also, the completion time interval estima-
	     tions will	have the estimated time	at which the dump will com-
	     plete printed at the end of the line.

     -T	date
	     Use the specified date as the starting time for the dump instead
	     of	the time determined from looking in /etc/dumpdates.  The for-
	     mat of date is the	same as	that of	ctime(3).  This	option is use-
	     ful for automated dump scripts that wish to dump over a specific
	     period of time.  The -T option is mutually	exclusive from the -u

     -u	     Update the	file /etc/dumpdates after a successful dump.  The for-
	     mat of /etc/dumpdates is readable by people, consisting of	one
	     free format record	per line: file system name, increment level
	     and ctime(3) format dump date.  There may be only one entry per
	     file system at each level.	 The file /etc/dumpdates may be	edited
	     to	change any of the fields, if necessary.	 If a list of files or
	     subdirectories is being dumped (as	opposed	to an entire file sys-
	     tem), then	-u is ignored.

     -x	snap-backup
	     Use a snapshot with snap-backup as	backup for this	dump.  See
	     fss(4) for	more details.

     -X	     Similar to	-x but uses a file system internal snapshot on the
	     file system to be dumped.

     -W	     dump tells	the operator what file systems need to be dumped.
	     This information is gleaned from the files	/etc/dumpdates and
	     /etc/fstab.  The -W option	causes dump to print out, for each
	     file system in /etc/dumpdates the most recent dump	date and
	     level, and	highlights those file systems that should be dumped.
	     If	the -W option is set, all other	options	are ignored, and dump
	     exits immediately.

     -w	     Is	like W,	but prints only	those file systems which need to be

     If	dump honors the	"nodump" flag (UF_NODUMP), files with the "nodump"
     flag will not be backed up.  If a directory has the "nodump" flag,	this
     directory and any file or directory under it will not be backed up.

     dump requires operator intervention on these conditions: end of tape, end
     of	dump, tape write error,	tape open error	or disk	read error (if there
     are more than a threshold of 32).	In addition to alerting	all operators
     implied by	the -n option, dump interacts with the operator	on dump's con-
     trol terminal at times when dump can no longer proceed, or	if something
     is	grossly	wrong.	All questions dump poses must be answered by typing
     "yes" or "no", appropriately.

     Since making a dump involves a lot	of time	and effort for full dumps,
     dump checkpoints itself at	the start of each tape volume.	If writing
     that volume fails for some	reason,	dump will, with	operator permission,
     restart itself from the checkpoint	after the old tape has been rewound
     and removed, and a	new tape has been mounted.

     dump tells	the operator what is going on at periodic intervals, including
     usually low estimates of the number of blocks to write, the number	of
     tapes it will take, the time to completion, and the time to the tape
     change.  The output is verbose, so	that others know that the terminal
     controlling dump is busy, and will	be for some time.

     In	the event of a catastrophic disk event,	the time required to restore
     all the necessary backup tapes or files to	disk can be kept to a minimum
     by	staggering the incremental dumps.  An efficient	method of staggering
     incremental dumps to minimize the number of tapes follows:

	   +o   Always start with a level 0 backup, for example:

		     /sbin/dump	-0u -f /dev/nrst1 /usr/src

	       This should be done at set intervals, say once a	month or once
	       every two months, and on	a set of fresh tapes that is saved

	   +o   After a level 0,	dumps of active	file systems are taken on a
	       daily basis, using a modified Tower of Hanoi algorithm, with
	       this sequence of	dump levels:

		     3 2 5 4 7 6 9 8 9 9 ...

	       For the daily dumps, it should be possible to use a fixed num-
	       ber of tapes for	each day, used on a weekly basis.  Each	week,
	       a level 1 dump is taken,	and the	daily Hanoi sequence repeats
	       beginning with 3.  For weekly dumps, another fixed set of tapes
	       per dumped file system is used, also on a cyclical basis.

     After several months or so, the daily and weekly tapes should get rotated
     out of the	dump cycle and fresh tapes brought in.

     If	dump receives a	SIGINFO	signal (see the	"status" argument of stty(1))
     whilst a backup is	in progress, statistics	on the amount completed, cur-
     rent transfer rate, and estimated finished	time, will be written to the
     standard error output.

     If	the following environment variables exist, they	are used by dump.

     TAPE	 If no -f option was specified,	dump will use the device spec-
		 ified via TAPE	as the dump device.  TAPE may be of the	form
		 "tapename", "host:tapename", or "user@host:tapename".

     RCMD_CMD	 dump will use RCMD_CMD	rather than rsh(1) to invoke rmt(8) on
		 the remote machine.

     TIMEFORMAT	 can be	used to	control	the format of the timestamps produced
		 by the	-t option.  TIMEFORMAT is a string containing embedded
		 formatting commands for strftime(3).  The total formatted
		 string	is limited to about 80 characters, if this limit is
		 exceeded then "ERROR: TIMEFORMAT too long, reverting to
		 default" will be printed and the time format will revert to
		 the default one.  If TIMEFORMAT is not	set then the format
		 string	defaults to "%T	%Z"

     /dev/nrst0	     default tape unit to use.	Taken from _PATH_DEFTAPE in
     /dev/rst*	     raw SCSI tape interface
     /etc/dumpdates  dump date records
     /etc/fstab	     dump table: file systems and frequency
     /etc/group	     to	find group operator

     Many, and verbose.

     dump exits	with zero status on success.  Startup errors are indicated
     with an exit code of 1; abnormal termination is indicated with an exit
     code of 3.

     chflags(1), rcmd(1), stty(1), wall(1), fts(3), rcmd(3), fss(4), st(4),
     fstab(5), environ(7), restore(8), rmt(8)

     A dump command appeared in	Version	6 AT&T UNIX.

     The -i flag was inspired by the -x	flag from Sun's	Solstice Backup	util-

     At	least the following caveats can	be mentioned.

     +o	 Fewer than 32 read errors on the file system are ignored.

     +o	 Each reel requires a new process, so parent processes for reels al-
	 ready written just hang around	until the entire tape is written.

     +o	 dump with the -W or -w	options	does not report	file systems that have
	 never been recorded in	/etc/dumpdates,	even if	listed in /etc/fstab.

     +o	 When dumping a	list of	files or subdirectories, access	privileges are
	 required to scan the directory	(as this is done via the fts(3)	rou-
	 tines rather than directly accessing the file system).

     +o	 It would be nice if dump knew about the dump sequence,	kept track of
	 the tapes scribbled on, told the operator which tape to mount when,
	 and provided more assistance for the operator running restore(8).

     +o	 Snapshot support is experimental.  Be sure you	have a backup before
	 you use it.

BSD			       November	5, 2010				   BSD


Want to link to this manual page? Use this URL:

home | help