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DUMP(8)                   System management commands                   DUMP(8)

       dump - ext2/3/4 filesystem backup

       dump  [-level#] [-ackMnqSuv] [-A file] [-B records] [-b blocksize] [-d density] [-D
       file] [-e inode numbers] [-E file] [-f file] [-F script] [-h level] [-I nr  errors]
       [-jcompression  level] [-L label] [-Q file] [-s feet] [-T date] [-y] [-zcompression
       level] files-to-dump

       dump [-W | -w]

       Dump examines files on an ext2/3/4 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  car-
       tridge  tape drives), each volume is of a fixed size; the actual size is determined
       by specifying cartridge media, or via 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  direc-
       tories  to be backed up as a subset of a 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 not
       allowed, the only dump level that is supported is 0 and all the files and  directo-
       ries must reside on the same filesystem.

       The following options are supported by dump:

              The  dump level (any integer). A level 0, full backup, specified by -0 guar-
              antees 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.
              Historically only levels 0 to 9 were usable in dump, this version is able to
              understand any integer as a dump level.

       -a     "auto-size". Bypass all tape length calculations, and write until an end-of-
              media  indication is returned.  This works best for most modern tape drives,
              and is the default. Use of this  option  is  particularly  recommended  when
              appending  to an existing tape, or using a tape drive with hardware compres-
              sion (where you can never be sure about the compression ratio).

       -A archive_file
              Archive a dump table-of-contents in the specified archive_file to be used by
              restore(8)  to  determine  whether  a file is in the dump file that is being

       -b blocksize
              The number of kilobytes per dump record. The default blocksize is 10, unless
              the -d option has been used to specify a tape density of 6250BPI or more, in
              which case the default blocksize is 32. Th maximal value is 1024.  Note how-
              ever  that,  since the IO system slices all requests into chunks of MAXBSIZE
              (which can be as low as 64kB), you can experience problems with dump(8)  and
              restore(8)  when  using a higher value, depending on your kernel and/or libC

       -B records
              The number of 1 kB blocks per volume. Not normally  required,  as  dump  can
              detect  end-of-media. When the specified size is reached, dump waits for you
              to change the volume.  This option overrides the calculation  of  tape  size
              based  on  length  and density. If compression is on this limits the size of
              the compressed output per volume.  Multiple values may be given as a  single
              argument  separated  by commas.  Each value will be used for one dump volume
              in the order listed; if dump creates more volumes than the number of  values
              given, the last value will be used for the remaining volumes. This is useful
              for filling up already partially filled media (and then continuing with full
              size volumes on empty media) or mixing media of different sizes.

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

       -d density
              Set tape density to density.  The default is 1600BPI. Specifying a tape den-
              sity overrides the end-of-media detection.

       -D file
              Set the path name of the file storing the  information  about  the  previous
              full and incremental dumps. The default location is /etc/dumpdates.

       -e inodes
              Exclude inodes from the dump. The inodes parameter is a comma separated list
              of inode numbers (you can use stat(1) to find the inode number for a file or

       -E file
              Read  list  of  inodes to be excluded from the dump from the text file file.
              The file file should be an ordinary file containing inode numbers  separated
              by newlines.

       -f file
              Write the backup to file; file may be a special device file like /dev/st0 (a
              tape drive), /dev/rsd1c (a floppy disk drive), an ordinary file, or  -  (the
              standard output). Multiple file names may be given as a single argument sep-
              arated 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  (which
              should  already  exist, dump doesn't create a new remote file) 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.

       -F script
              Run  script  at  the end of each tape (except for the last one).  The device
              name and the current volume number are  passed  on  the  command  line.  The
              script  must  return  0  if  dump should continue without asking the user to
              change the tape, 1 if dump should continue but ask the user  to  change  the
              tape.  Any  other  exit code will cause dump to abort. For security reasons,
              dump reverts back to the real user ID and the real group ID  before  running
              the script.

       -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.

       -I nr errors
              By  default,  dump  will  ignore the first 32 read errors on the file system
              before asking for operator intervention. You can change this using this flag
              to any value. This is useful when running dump on an active filesystem where
              read errors simply indicate an inconsistency between the mapping and dumping

              A value of 0 means that all read errors will be ignored.

       -jcompression level
              Compress  every  block  to  be written on the tape using bzlib library. This
              option will work only when dumping to a file or pipe or, when dumping  to  a
              tape  drive, if the tape drive is capable of writing variable length blocks.
              You will need at least the 0.4b24 version of restore  in  order  to  extract
              compressed  tapes.  Tapes  written  using compression will not be compatible
              with the BSD tape format. The (optional) parameter specifies the compression
              level  bzlib  will  use. The default compression level is 2. If the optional
              parameter is specified, there should be no white space  between  the  option
              letter and the parameter.

       -k     Use  Kerberos authentication to talk to remote tape servers. (Only available
              if this option was enabled when dump was compiled.)

       -L label
              The user-supplied text string label is placed into the  dump  header,  where
              tools  like  restore(8)  and  file(8) can access it. Note that this label is
              limited to be at most LBLSIZE (currently 16) characters, which must  include
              the terminating \0.

       -m     If  this  flag is specified, dump will optimise the output for inodes having
              been changed but not modified since the last dump ('changed' and  'modified'
              have the meaning defined in stat(2) ). For those inodes, dump will save only
              the metadata, instead of saving the entire inode contents.  Inodes which are
              either  directories or have been modified since the last dump are saved in a
              regular way. Uses of this flag must be consistent, meaning that either every
              dump in an incremental dump set have the flag, or no one has it.

              If  you  use this option, be aware that many programs that unpack files from
              archives (e.g. tar, rpm, unzip, dpkg) may set files' mtimes to dates in  the
              past.   Files  installed in this way may not be dumped correctly using "dump
              -m" if the modified mtime is earlier than the previous level dump.

              Tapes written using such 'metadata only' inodes will not be compatible  with
              the BSD tape format or older versions of restore.

       -M     Enable  the  multi-volume feature. The name specified with f is treated as a
              prefix and dump writes in sequence to <prefix>001, <prefix>002 etc. This can
              be useful when dumping to files on an ext2/3/4 partition, in order to bypass
              the 2GB file size limitation.

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

       -q     Make dump abort immediately whenever operator attention is required, without
              prompting in case of write errors, tape changes etc.

       -Q file
              Enable the Quick File Access support. Tape  positions  for  each  inode  are
              stored into the file file which is used by restore (if called with parameter
              -Q and the filename) to directly position the tape at the  file  restore  is
              currently  working  on.  This  saves  hours when restoring single files from
              large backups, saves the tapes and the drive's head.

              It is recommended to set up the st driver to return logical  tape  positions
              rather  than  physical before calling dump/restore with parameter -Q.  Since
              not all tape devices support physical  tape  positions  those  tape  devices
              return an error during dump/restore when the st driver is set to the default
              physical setting.  Please see the st(4) man page, option MTSETDRVBUFFER , or
              the  mt(1)  man  page, on how to set the driver to return logical tape posi-

              Before calling restore with parameter -Q, always make sure the st driver  is
              set  to  return the same type of tape position used during the call to dump.
              Otherwise restore may be confused.

              This option can be used when dumping to local tapes (see above) or to  local

       -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.
              Specifying the tape size overrides end-of-media detection.

       -S     Size estimate. Determine the amount of space that is needed to  perform  the
              dump without actually doing it, and display the estimated number of bytes it
              will take. This is useful with incremental dumps to determine how many  vol-
              umes of media will be needed.

       -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) followed by an rfc822 timezone specification: either a
              plus or minus sign followed by two digits for the number of  hours  and  two
              digits  for  the minutes.  For example, -0800 for eight hours west of Green-
              wich or +0230 for two hours and a half east of Greenwich. This timezone off-
              set  takes  into  account  daylight savings time (if applicable to the time-
              zone): UTC offsets when daylight savings time is in effect will be different
              than  offsets when daylight savings time is not in effect. For backward com-
              patibility, if no timezone is specified, a  local  time  is  assumed.   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

       -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
              followed by a rfc822 timezone specification (see the -u option for details).
              If no timezone offset is specified, times are interpreted as local. Whenever
              the file is written, all dates in the file are converted to the  local  time
              zone,  without  changing  the  UTC  times.  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.

       -v     The  -v (verbose) makes dump to print extra information which could be help-
              ful in debug sessions.

       -W     Dump tells the operator what file systems need to be dumped.  This  informa-
              tion is gleaned from the files /etc/dumpdates and /etc/fstab.  The -W option
              causes dump to print out, for all file systems in /etc/dumpdates , and  rec-
              ognized file systems in /etc/mtab and /etc/fstab.  the most recent dump date
              and level, and highlights those 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  recognized  filesystems  in  /etc/mtab and
              /etc/fstab which need to be dumped.

       -y     Compress every block to be written to the tape using the lzo library.   This
              doesn't  compress  as  well  as the zlib library but it's much faster.  This
              option will work only when dumping to a file or pipe or, when dumping  to  a
              tape  drive, if the tape drive is capable of writing variable length blocks.
              You will need at least the 0.4b34 version of restore  in  order  to  extract
              compressed  tapes.  Tapes  written  using compression will not be compatible
              with the BSD tape format.

       -zcompression level
              Compress every block to be written on the  tape  using  zlib  library.  This
              option  will  work only when dumping to a file or pipe or, when dumping to a
              tape drive, if the tape drive is capable of writing variable length  blocks.
              You  will  need  at  least the 0.4b22 version of restore in order to extract
              compressed tapes. Tapes written using compression  will  not  be  compatible
              with the BSD tape format. The (optional) parameter specifies the compression
              level zlib will use. The default compression level is  2.  If  the  optional
              parameter  is  specified,  there should be no white space between the option
              letter and the parameter.

       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 nr errors). 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 check-
       points 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 check-
       point after the old tape has been rewound and removed, and  a  new  tape  has  been

       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

       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/st0 /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,
              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 cycli-
              cal basis.

       After several months or so, the daily and weekly tapes should get  rotated  out  of
       the dump cycle and fresh tapes brought in.

       Another backup strategy is the Tower of Hanoi sequence, which reuses older tapes in
       a way that for newer dates the available restore points are more frequent, then for
       older dates (see http://en.wikipedia.org/wiki/Backup_rotation_scheme for additional

       (The 4.3BSD option syntax is implemented for backward compatibility but is not doc-
       umented here.)

       TAPE   If  no  -f option was specified, dump will use the device specified via TAPE
              as the dump device.  TAPE may be of the  form  tapename,  host:tapename,  or

       RMT    The  environment  variable RMT will be used to determine the pathname of the
              remote rmt(8) program.

       RSH    Dump uses the contents of this variable to determine the name of the  remote
              shell  command  to  use  when  doing remote backups (rsh, ssh etc.). If this
              variable is not set, rcmd(3) will be used, but only root will be able to  do
              remote backups.

              default tape unit to dump to

              dump date records

              dump table: file systems and frequency

              dump table: mounted file systems

              to find group operator

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

       Many, and verbose.

       The  format  of the /etc/dumpdates file has changed in release 0.4b34, however, the
       file will be read correctly with either pre-0.4b34 or 0.4b34 and later versions  of
       dump provided that the machine on which dump is run did not change timezones (which
       should be a fairly rare occurrence).

       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.

       It  might  be  considered  a bug that this version of dump can only handle ext2/3/4
       filesystems.  Specifically, it does not work with FAT filesystems.

       Fewer than 32 read errors (change this with -I) on the filesystem are  ignored.  If
       noticing  read  errors is important, the output from dump can be parsed to look for
       lines that contain the text 'read error'.

       When a read error occurs, dump prints out the corresponding physical disk block and
       sector  number and the ext2/3/4 logical block number. It doesn't print out the cor-
       responding file name or even the inode number. The user has to use debugfs(8), com-
       mands ncheck and icheck to translate the ext2blk number printed out by dump into an
       inode number, then into a file name.

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

       The estimated number of tapes is not correct if compression is on.

       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  assis-
       tance for the operator running restore.

       Dump  cannot  do remote backups without being run as root, due to its security his-
       tory.  Presently, it works if you set it setuid (like it  used  to  be),  but  this
       might  constitute  a security risk. Note that you can set RSH to use a remote shell
       program instead.

       The dump/restore backup suite was ported to Linux's Second Extended File System  by
       Remy  Card  <card AT Linux.Org>. He maintained the initial versions of dump (up and
       including 0.4b4, released in January 1997).

       Starting with 0.4b5, the new maintainer is Stelian Pop <stelian AT popies.net>.

       The dump/restore backup suite is available from <http://dump.sourceforge.net>

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

BSD                     version 0.4b42 of June 18, 2009                DUMP(8)

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