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

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
DUMP(8)			FreeBSD	System Manager's Manual		       DUMP(8)

NAME
     dump, rdump -- filesystem backup

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

     rdump is an alternate name	for dump.

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

DESCRIPTION
     Dump examines files on a filesystem and determines	which files need to be
     backed up.	 These files are copied	to the given disk, tape	or other stor-
     age 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 prompt-
     ing the operator to change	media.

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

     The following options are supported by dump:

     -0-9    Dump levels.  A level 0, full backup, guarantees the entire
	     filesystem	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 kilobytes per output	volume,	except that if it is
	     not an integer multiple of	the output block size, the command
	     uses the next smaller such	multiple.  This	option overrides the
	     calculation of tape size based on length and density.

     -b	blocksize
	     The number	of kilobytes per output	block, except that if it is
	     larger than 64, the command uses 64. (See the BUGS	section.)  The
	     default block size	is 10.

     -c	     Change the	defaults for use with a	cartridge tape drive, with a
	     density of	8000 bpi, and a	length of 1700 feet.

     -D	dumpdates
	     Specify an	alternate path to the dumpdates	file.  The default is
	     /etc/dumpdates.

     -d	density
	     Set tape density to density.  The default is 1600BPI.

     -f	file
	     Write the backup to file; file may	be a special device file like
	     /dev/sa0 (a tape drive), /dev/fd1 (a floppy disk drive), an ordi-
	     nary 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
	     requires more volumes than	the number of names given, the last
	     file name will used for all remaining volumes after prompting for
	     media 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).  The	default	path name of
	     the remote	rmt(8) program is /etc/rmt; this can be	overridden by
	     the environment variable RMT.

     -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
	     incremental backups omit such files but full backups retain them.

     -k	     Use Kerberos authentication to talk to remote tape	servers.
	     (Only available if	this option was	enabled	when dump was com-
	     piled.)

     -n	     Whenever dump requires operator attention,	notify all operators
	     in	the group ``operator'' by means	similar	to a wall(1).

     -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.

     -T	date
	     Use the specified date as the starting time for the dump instead
	     of	the time determined from looking in the	dumpdates file.	 The
	     format of date is the same	as that	of ctime(3).  This option is
	     useful for	automated dump scripts that wish to dump over a	spe-
	     cific period of time.  The	-T option is mutually exclusive	from
	     the -u option.

     -u	     Update the	dumpdates file after a successful dump.	 The format of
	     the dumpdates file	is readable by people, consisting of one free
	     format record per line: filesystem	name, increment	level and
	     ctime(3) format dump date.	 There may be only one entry per
	     filesystem	at each	level.	The dumpdates file may be edited to
	     change any	of the fields, if necessary.  The default path for the
	     dumpdates file is /etc/dumpdates, but the -D option may be	used
	     to	change it.

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

     -w	     Is	like W,	but prints only	those filesystems which	need to	be
	     dumped.

     Directories and regular files which have their ``nodump'' flag
     (UF_NODUMP) set will be omitted along with	everything under such directo-
     ries, subject to the -h option.

     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 key, dump interacts with	the operator on	dump's control
     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 -- every 5
     minutes, or promptly after	receiving SIGINFO -- 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 out-
     put 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/nsa0 /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
	       forever.

	   +o   After a level 0,	dumps of active	filesystems 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 filesystem 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.

ENVIRONMENT
     The environment variable RMT will be used to determine the	pathname of
     the remote	rmt(8) program.

FILES
     /dev/sa0	     default tape unit to dump to
     /etc/dumpdates  dump date records (this can be changed; see the -D
		     option)
     /etc/fstab	     dump table: filesystems and frequency
     /etc/group	     to	find group operator

SEE ALSO
     chflags(1), fstab(5), restore(8), rmt(8)

DIAGNOSTICS
     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.

BUGS
     Fewer than	32 read	errors on the filesystem are ignored.

     Each reel requires	a new process, so parent processes for reels already
     written just hang around until the	entire tape is written.

     Currently,	physio(9) slices all requests into chunks of 64	KB.  There-
     fore, it is impossible to use a larger output block size, so dump will
     prevent this from happening.

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

     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 pro-
     vided more	assistance for the operator running restore.

     Dump cannot do remote backups without being run as	root, due to its secu-
     rity history.  This will be fixed in a later version of FreeBSD.
     Presently,	it works if you	set it setuid (like it used to be), but	this
     might constitute a	security risk.

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

FreeBSD	10.1			 July 9, 2001			  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | ENVIRONMENT | FILES | SEE ALSO | DIAGNOSTICS | BUGS | HISTORY

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=dump&sektion=8&manpath=FreeBSD+4.6-RELEASE>

home | help