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NAME    [Toc]    [Back]

     dump - filesystem backup

SYNOPSIS    [Toc]    [Back]

     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
          but is not documented here.)

DESCRIPTION    [Toc]    [Back]

     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.  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 after
 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 device
  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 default
 level is 0.

     -a      ``auto-size''.  Bypass all  tape  length  considerations, and enforce
  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

     -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

     -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 requires
 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
             ``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
             backups omit such  files  but  full  backups  retain

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

     -s feet
             Attempt  to calculate the amount of tape needed at a
             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 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 flag is  mutually  exclusive
from the -u

     -u       Update  the  file /etc/dumpdates after a successful
dump.  The format
 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 filesystem),
 then -u is ignored.

     -W      dump tells the operator what file systems need to be
             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 immediately.

     -w      Same as -W, but prints only those filesystems  which
need to be

     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 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
     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
     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
     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

           +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 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

     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 completed,
 current transfer rate, and estimated finished  time,
will be written
 to the standard error output.

ENVIRONMENT    [Toc]    [Back]

     TAPE             default  tape  device  to  use  instead  of

FILES    [Toc]    [Back]

     /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    [Toc]    [Back]

     Many, and verbose.

     dump exits with zero status on success.  Startup errors  are
     with  an  exit  code of 1; abnormal termination is indicated
with an exit
     code of 3.

SEE ALSO    [Toc]    [Back]

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

HISTORY    [Toc]    [Back]

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

BUGS    [Toc]    [Back]

     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

     When dumping a list of files or subdirectories, access privileges are required
 to scan the directory (as this is done via the fts(3)
     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 provided
 more assistance for the operator running restore(8).

OpenBSD      3.6                           June      4,      1997
[ Back ]
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