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NetBSD 6.1.5 - man page for dump (netbsd section 8)

DUMP(8) 			   BSD System Manager's Manual				  DUMP(8)

NAME
     dump, rdump -- file system backup

SYNOPSIS
     dump [-0123456789aceFinStuX] [-B records] [-b blocksize] [-d density] [-f file] [-h level]
	  [-k read-blocksize] [-L label] [-l timeout] [-r cachesize] [-s feet] [-T date]
	  [-x snap-backup] files-to-dump
     dump [-W | -w]

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

DESCRIPTION
     dump examines files on a file system 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.  This can be enforced by using the -a option.

     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 the tape size and
     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 single file system, or a list of files and directories on a single
     file system to be backed up as a subset of the file system.  In the former case,
     files-to-dump may be the device of a file system, the path to a currently mounted file sys-
     tem, the path to an unmounted file system listed in /etc/fstab, or, if -F is given, a file
     system image.  In the latter case, certain restrictions are placed on the backup: -u is
     ignored, the only dump level that is supported is -0, and all of the files must reside on
     the same file system.

     Any files with the superuser "log" flag (SF_LOG) set will be skipped.  These files are
     assumed to be wapbl(4) journal files and will not be backed up.

     The following options are supported by dump:

     -0-9    Dump levels.  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
	     (but see also the -i option below).  The default level is 9.

     -a      ``auto-size''.  Bypass all tape length considerations, and enforce writing until an
	     end-of-media indication is returned.  This fits best for most modern tape drives.
	     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).

     -B records
	     The number of kilobytes per volume, rounded down to a multiple of the blocksize.
	     This option overrides the calculation of tape size based on length and density.

     -b blocksize
	     The number of kilobytes per dump record.

     -c      Modify the calculation of the default density and tape size to be more appropriate
	     for cartridge tapes.

     -d density
	     Set tape density to density.  The default is 1600 Bits Per Inch (BPI).

     -e      Eject tape automatically if a tape change is required.

     -F      Indicates that files-to-dump is a file system image.

     -f file
	     Write the backup to file; file may be a special device file like /dev/rst0 (a tape
	     drive), /dev/rsd1c (a 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 remain-
	     ing 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 using rmt(8).  Note that methods more secure than rsh(1) (such as ssh(1)) can
	     be used to invoke rmt(8) on the remote host, via the environment variable RCMD_CMD.
	     See rcmd(3) for more details.

     -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      The dump is treated as level 9 but takes into account a previous level 9, if one
	     exists.  This makes it possible to perform a ``true incremental'' dump.

     -k read-blocksize
	     The size in kilobyte of the read buffers, rounded up to a multiple of the file sys-
	     tem block size.  Default is 32k.

     -l timeout
	     If a tape change is required, eject the tape and wait for the drive to be ready
	     again.  This is to be used with tape changers which automatically load the next tape
	     when the tape is ejected.	If after the timeout (in seconds) the drive is not ready
	     dump falls back to the default behavior, and prompts the operator for the next tape.

     -L label
	     The user-supplied text string label is placed into the dump header, where tools like
	     restore(8) and file(1) can access it.  Note that this label is limited to be at most
	     LBLSIZE (currently 16) characters, which must include the terminating '\0'.

     -n      Whenever dump requires operator attention, notify all operators in the group
	     "operator" using wall(1).

     -r cachesize
	     Use that many buffers for read cache operations.  A value of zero disables the read
	     cache altogether, higher values improve read performance by reading larger data
	     blocks from the disk and maintaining them in an LRU cache.  See the -k option for
	     the size of the buffers.  Maximum is 512, the size of the cache is limited to 15% of
	     the avail RAM by default.

     -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 con-
	     servative on this option.	The default tape length is 2300 feet.

     -S      Display an estimate of the backup size and the number of tapes required, and exit
	     without actually performing the dump.

     -t      All informational log messages printed by dump will have the time prepended to them.
	     Also, the completion time interval estimations will have the estimated time at which
	     the dump will complete printed at the end of the line.

     -T date
	     Use the specified date as the starting time for the dump instead of the time deter-
	     mined from looking in /etc/dumpdates.  The format of date is the same as that of
	     ctime(3).	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 people, consisting of one free format record per line:
	     file system name, increment level and ctime(3) format dump date.  There may be only
	     one entry per file system at each level.  The file /etc/dumpdates may be edited to
	     change any of the fields, if necessary.  If a list of files or subdirectories is
	     being dumped (as opposed to an entire file system), then -u is ignored.

     -x snap-backup
	     Use a snapshot with snap-backup as backup for this dump.  See fss(4) for more
	     details.

     -X      Similar to -x but uses a file system internal snapshot on the file system to be
	     dumped.

     -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 each file system in /etc/dumpdates the most recent dump date and
	     level, and highlights those file systems 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 those file systems which need to be dumped.

     If dump honors the "nodump" flag (UF_NODUMP), files with the "nodump" flag will not be
     backed up.  If a directory has the "nodump" flag, this directory and any file or directory
     under it will not be backed up.

     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 are more than a threshold of 32).
     In addition to alerting all operators implied by the -n option, dump interacts with the
     operator on dump's control terminal at times when dump can no longer proceed, or if some-
     thing 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 esti-
     mates of the number of blocks to write, the number of tapes it will take, the time to com-
     pletion, 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:

	   o   Always start with a level 0 backup, for example:

		     /sbin/dump -0u -f /dev/nrst1 /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.

	   o   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.

     If dump receives a SIGINFO signal (see the "status" argument of stty(1)) whilst a backup is
     in progress, statistics on the amount completed, current transfer rate, and estimated fin-
     ished time, will be written to the standard error output.

ENVIRONMENT
     If the following environment variables exist, they are used by dump.

     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".

     RCMD_CMD	 dump will use RCMD_CMD rather than rsh(1) to invoke rmt(8) on the remote
		 machine.

     TIMEFORMAT  can be used to control the format of the timestamps produced by the -t option.
		 TIMEFORMAT is a string containing embedded formatting commands for strftime(3).
		 The total formatted string is limited to about 80 characters, if this limit is
		 exceeded then "ERROR: TIMEFORMAT too long, reverting to default" will be printed
		 and the time format will revert to the default one.  If TIMEFORMAT is not set
		 then the format string defaults to "%T %Z"

FILES
     /dev/nrst0      default tape unit to use.	Taken from _PATH_DEFTAPE in /usr/include/paths.h.
     /dev/rst*	     raw SCSI tape interface
     /etc/dumpdates  dump date records
     /etc/fstab      dump table: file systems and frequency
     /etc/group      to find group operator

DIAGNOSTICS
     Many, and verbose.

     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.

SEE ALSO
     chflags(1), rcmd(1), stty(1), wall(1), fts(3), rcmd(3), fss(4), st(4), fstab(5), environ(7),
     restore(8), rmt(8)

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

     The -i flag was inspired by the -x flag from Sun's Solstice Backup utility.

BUGS
     At least the following caveats can be mentioned.

     o	 Fewer than 32 read errors on the file system are ignored.

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

     o	 dump with the -W or -w options does not report file systems that have never been
	 recorded in /etc/dumpdates, even if listed in /etc/fstab.

     o	 When dumping a list of files or subdirectories, access privileges are required to scan
	 the directory (as this is done via the fts(3) routines rather than directly accessing
	 the file system).

     o	 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(8).

     o	 Snapshot support is experimental.  Be sure you have a backup before you use it.

BSD					 November 5, 2010				      BSD


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