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

NAME
     dump — filesystem backup

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

     (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.  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 options below.	 By default, the same
     output file name is used for each volume after prompting the operator to
     change media.

     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 the same or lower level.
	     The default level is 9.

     -B records
	     The number of dump records per volume.  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 1600BPI.

     -f file
	     Write the backup to file; file may be a special device file like
	     /dev/rmt12 (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
	     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).

     -h level
	     Honor the user “nodump” flag 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.

     -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 /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
	     option.

     -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: filesystem name, increment level and
	     ctime(3) format dump date.	 There may be only one entry per
	     filesystem at each level.	The file /etc/dumpdates may be edited
	     to change any of the fields, if necessary.

     -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 filesystems which need to be
	     dumped.

     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, 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:

	   ·   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
	       forever.

	   ·   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.

FILES
     /dev/rmt8	     default tape unit to dump to
     /etc/dumpdates  dump date records
     /etc/fstab	     dump table: file systems and frequency
     /etc/group	     to find group operator

SEE ALSO
     restore(8), rmt(8), dump(5), fstab(5)

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.

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

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

4th Berkeley Distribution	  May 1, 1995	     4th Berkeley Distribution
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