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       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 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
       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 filesystem.


       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. 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
              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  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 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
              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

       -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

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

       -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

       -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

       -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 /var/lib/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
              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 specific period of time. The  -T  option  is
              mutually exclusive from the -u option.

       -u     Update  the file /var/lib/dumpdates after a successful dump. The
              format of /var/lib/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 /var/lib/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 helpful in debug sessions.

       -W     Dump tells the operator what file systems  need  to  be  dumped.
              This  information  is  gleaned from the files /var/lib/dumpdates
              and /etc/fstab.  The -W option causes dump to print out, for all
              file systems in /var/lib/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

       -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

       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,
       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 -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

       —      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 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

       (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  /var/lib/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
       ext2/3/4  filesystems.   Specifically,  it  does  not  work  with   FAT

       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 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 <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


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