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

NAME
     dump - filesystem backup

SYNOPSIS
     dump [-0123456789acnu] [-B records] [-b blocksize] [-d density] [-f file]
          [-h level] [-s feet] [-T date] files-to-dump
     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.  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, density and/or block count options
     below.  By default, the same output file name is used for each volume af-
     ter prompting the operator to change media.

     files-to-dump is either a mountpoint of a filesystem or a list of files
     and directories on a single filesystem to be backed up as a subset of the
     filesystem.  In the former case, either the path to a mounted filesystem
     or the device of an unmounted filesystem can be used.  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 filesystem.

     Rewinding or ejecting tape features after a close operation on a tape de-
     vice depend on the name of the tape unit device used.  See the -f option
     and st(4) for more information.

     The options are as follows:

     -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.  The de-
             fault level is 0.

     -a      ``auto-size''.  Bypass all tape length considerations, and en-
             force writing until an end-of-media indication is returned.  This
             option is recommended 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 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.  Since the IO system
             slices all requests into chunks of MAXBSIZE (typically 64KB), it
             is not possible to use a larger blocksize without having problems
             later with restore(8).  Therefore dump will constrain writes to
             MAXBSIZE.

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

     -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/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 be 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 flag is mutually exclusive from the -u
             flag.

     -u      Update the file /etc/dumpdates after a successful dump.  The for-
             mat of /etc/dumpdates is human readable, 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.  If a list of files or
             subdirectories is being dumped (as opposed to an entire filesys-
             tem), then -u is ignored.

     -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 flag 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 flag is set, all other options are ignored, and dump exits im-
             mediately.

     -w      Same as -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
     is more than a threshold of 32).  In addition to alerting all operators
     implied by the -n flag, 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
               forever.

           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 com-
     pleted, current transfer rate, and estimated finished time, will be writ-
     ten to the standard error output.

ENVIRONMENT
     TAPE            default tape device to use instead of /dev/rst0

FILES
     /dev/rst0       default tape unit to dump to
     /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

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.

SEE ALSO
     stty(1), fts(3), rcmd(3), st(4), fstab(5), restore(8), rmt(8)

HISTORY
     A dump command appeared in Version 5 AT&T UNIX.

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 flag does not report filesystems that have never
     been recorded in /etc/dumpdates, even if listed in /etc/fstab.

     When dumping a list of files or subdirectories, access privileges are re-
     quired to scan the directory (as this is done via the fts(3) routines
     rather than directly accessing the filesystem).

     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).

OpenBSD 3.6                      June 4, 1997                                4