dump

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

NAME
     dump — filesystem backup

SYNOPSIS
     dump [0123456789BbhfusTdWn [argument ...]] filesystem
     dump [0123456789BbhfusTdWn [argument ...]] directory

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
     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.  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 is interpreted as the
           size in kilobytes).  This option overrides the calculation of tape
           size based on length and density.

     b blocksize
           The number of kilobytes per dump record.

     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.

     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).

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

     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.

     u     Update the file /etc/dumpdates after a successful dump.  The format
           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.

     T date
           Use the specified date as the starting time for the dump instead of
           the time determined from looking in /etc/dumpdates.  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 specific period of
           time.  The T option is mutually exclusive from the u option.

     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 0uf /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
               number 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), chattr(1), 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
     provided more assistance for the operator running restore.

     The Linux port of dump is not able yet to produce correct multi-volume
     backups.

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

4th Berkeley Distribution        June 16, 1993       4th Berkeley Distribution