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DUMP(8)                   System management commands                   DUMP(8)

       dump - ext2/3 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 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 vol-
       ume is of a fixed size; the actual size is determined by specifying cartridge media, or via the tape size, den-
       sity 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 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 directories must reside on  the  same

       The following options are supported by dump:

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

       -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  par-
              ticularly  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 restored.

       -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  however  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 versions.

       -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  calcula-
              tion  of  tape  size  based on length and density. If compression is on this limits the size of the com-
              pressed 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 density 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 directory).

       -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 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  (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  com-
              pressed  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

       -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

              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 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 positions.

              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 files.

       -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 volumes 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 Greenwich or +0230 for two hours and a half
              east  of  Greenwich. This timezone offset takes into account daylight savings time (if applicable to the
              timezone): UTC offsets when daylight savings time is in effect will be different than offsets when  day-
              light  savings  time  is not in effect. For backward compatibility, if no timezone is specified, a local
              time is assumed.  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.

       -u     Update the file /etc/dumpdates after a successful dump. The format of /etc/dumpdates is readable by peo-
              ple, 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  neces-

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

       -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  all  file  systems  in
              /etc/dumpdates , and recognized 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 dump-
              ing 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 param-

       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 opera-
       tors 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

       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  incre-
       mental 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
                     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.

       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 for additional information).

       (The 4.3BSD option syntax is implemented for backward compatibility but is not documented 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 user@host:tapename.

       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 termina-
       tion is indicated with an exit code of 3.

       It might be considered a bug that this version of dump can only handle ext2/3  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  logical  block  number.  It doesn't print out the corresponding file name or even the inode number. The
       user has to use debugfs(8), commands 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 assistance for the operator running restore.

       Dump  cannot  do remote backups without being run as root, due to its security history.  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
       <cardATLinux.Org>. He maintained the initial versions of dump (up and including 0.4b4,  released  in  January

       Starting with 0.4b5, the new maintainer is Stelian Pop <>.

       The dump/restore backup suite is available from <>;

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

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