dump

DUMP(8) System management commands DUMP(8)

NAME

   dump - ext2/3/4 filesystem backup

SYNOPSIS

   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]

DESCRIPTION

   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  stor‐
   age 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  de‐
   termined  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 can be a filesystem identifier or a list of files and directories to be backed up.

   A filesystem can be identified by its device path (e.g.  /dev/sde2), by its mountpoint if the filesystem is currently mounted (e.g.  /var), or by  its  label
   or uuid property if the block device is known to blkid(8) (e.g.  LABEL=foobar or UUID=a0f155-...).

   If  files-to-dump  is a list of files and directories, then certain restrictions apply: -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.

OPTIONS

   The following options are supported by dump:

   -level#
          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  MAXB‐
          SIZE (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 use‐
          ful 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 /var/lib/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 over‐
          ridden 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 passes.

          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‐
          tions.

          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 /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  time‐
          zone offset takes into account daylight savings time (if applicable to the timezone): UTC offsets when daylight savings time is in effect will be dif‐
          ferent 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 op‐
          tion.

   -u     Update the file /var/lib/dumpdates after a successful dump. The format of /var/lib/dumpdates is human-readable, with one record per  line.  Each  line
          holds, separated by spaces, a filesystem identifier, dump increment level and dump date in ctime(3) format followed by a rfc822 timezone specification
          (see the -T 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.

          The  filesystem identifier is exactly as given on the command line, e.g.  UUID=a0f155-...  or /dev/sde2.  This is for incremental dumps of filesystems
          on removable media or other situations where the device path changes over time. There may be at most one  entry  per  filesystem  for  each  increment
          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 op‐
          tion 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 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 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  stagger‐
   ing 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 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 fre‐
   quent, then for older dates (see https://en.wikipedia.org/wiki/Backup_rotation_scheme for additional information).

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

ENVIRONMENT

   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.

FILES

   /dev/st0
          default tape unit to dump to

   /var/lib/dumpdates
          dump date records

   /etc/fstab
          dump table: file systems and frequency

   /etc/mtab
          dump table: mounted file systems

   /etc/group
          to find group operator