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 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 oper-
       ator 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 filesystem.


       The following options are supported by dump:

              The dump level (any integer). 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 9. 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 compression (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 den-
              sity  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 calculation of tape size based on length and den-
              sity. 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

       -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 prompt-
              ing 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 incre-
              mental 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  com-
              patible with the BSD tape format. The (optional) parameter spec-
              ifies the compression level bzlib will use. The default compres-
              sion  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  com-

       -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.

              Tapes written using such ’metadata only’ inodes will not be com-
              patible 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

              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

       -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  fol-
              lowed  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 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  daylight
              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 spe-
              cific period of time. The -T option is mutually  exclusive  from
              the -u option.

       -u     Update the file /etc/dumpdates after a successful dump. The for-
              mat 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/dump-
              dates may be edited to change any of the fields, if necessary.

       -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 regognized 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  com-
              pressed  tapes. Tapes written using compression will not be com-
              patible 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  com-
              pressed  tapes. Tapes written using compression will not be com-
              patible with the BSD tape format. The (optional) parameter spec-
              ifies  the compression level zlib will use. The default compres-
              sion level is 2. If the optional parameter is  specified,  there
              should  be  no  white  space  between  the option letter and the

       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  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, includ-
       ing  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 mini-
       mum by staggering the incremental dumps. An efficient method  of  stag-
       gering 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 for-

       —      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.

       (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 speci-
              fied via TAPE as the dump device.  TAPE may be of the form tape-
              name, host:tapename, or user@host:tapename.

       RMT    The environment variable RMT will be used to determine the path-
              name 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


       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 filesystems.  Specifically, it does not work with  FAT  filesys-

       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 corresponing 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 <card@Linux.EU.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


       The  dump/restore  backup  suite is available from <http://dump.source-


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

BSD                      version 0.4b40 of May 2, 2005                 DUMP(8)

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