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

     dump, rdump -- file system backup

     dump [-0123456789acLnSu] [-B records] [-b blocksize] [-C cachesize]
          [-D dumpdates] [-d density] [-f file | -P pipecommand] [-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.)

     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 prompt-
     ing 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 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 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 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.  The default block size
             is 10.

     -C cachesize
             Specify the cache size in megabytes.  This will greatly improve
             performance at the cost of dump possibly not noticing changes in
             the file system between passes.  It is recommended that you
             always use this option when dumping a snapshot.  Beware that dump
             forks, and the actual memory use may be larger than the specified
             cache size.  The recommended cache size is between 8 and 32

     -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

     -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.

     -P pipecommand
             Use popen(3) to execute the sh(1) script string defined by
             pipecommand for the output device of each volume.  This child
             pipeline's stdin (/dev/fd/0) is redirected from the dump output
             stream, and the environment variable DUMP_VOLUME is set to the
             current volume number being written.  After every volume, the
             writer side of the pipe is closed and pipecommand is executed
             again.  Subject to the media size specified by -B, each volume is
             written in this manner as if the output were a tape drive.

     -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.

     -L      This option is to notify dump that it is dumping a live file sys-
             tem.  To obtain a consistent dump image, dump takes a snapshot of
             the file system in the .snap directory in the root of the file
             system being dumped and then does a dump of the snapshot.  The
             snapshot is unlinked as soon as the dump starts, and is thus
             removed when the dump is complete.  This option is ignored for
             unmounted or read-only file systems.  If the .snap directory does
             not exist in the root of the file system being dumped, a warning
             will be issued and the dump will revert to the standard behavior.
             This problem can be corrected by creating a .snap directory in
             the root of the file system to be dumped; its owner should be
             ``root'', its group should be ``operator'', and its mode should
             be ``0770''.

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

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

     -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: file system name, increment level and
             ctime(3) format dump date.  There may be only one entry per file
             system 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      Tell the operator what file systems 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 file system in
             the dumpdates file the most recent dump date and level, and high-
             lights those file systems that should be dumped.  If the -W
             option is set, all other options are ignored, and dump exits

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

     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.

     The dump utility 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 alert-
     ing 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.

     The dump utility tells the operator what is going on at periodic inter-
     vals (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 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/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

           +o   After a level 0, dumps of active file systems (file systems
               with files that change, depending on your partition layout some
               file systems may contain only data that does not change) are
               taken on a daily basis, using a modified Tower of Hanoi algo-
               rithm, 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.

     TAPE  The file or device to dump to if the -f option is not used.

     RMT   Pathname of the remote rmt(8) program.

     RSH   Pathname of a remote shell program, if not rsh(1).

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

     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.

     Many, and verbose.

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

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

     Fewer than 32 read errors on the file system are ignored, though all
     errors will generate a warning message.  This is a bit of a compromise.
     In practice, it is possible to generate read errors when doing dumps on
     mounted partitions if the file system is being modified while the dump is
     running.  Since dumps are often done in an unattended fashion using
     cron(8) jobs asking for Operator intervention would result in the dump
     dying.  However, there is nothing wrong with a dump tape written when
     this sort of read error occurs, and there is no reason to terminate the

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

     The dump utility with the -W or -w options does not report file systems
     that have never been recorded in the dumpdates file, even if listed in

     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(8).

     The dump utility cannot do remote backups without being run as root, due
     to its security 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.

FreeBSD 6.2                    February 24, 2006                   FreeBSD 6.2


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