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29 .\" @(#)dump.8 8.3 (Berkeley) 5/1/95
38 .Nd file system backup
41 .Op Fl 0123456789acLnSu
47 .Op Fl f Ar file | Fl P Ar pipecommand
56 is an alternate name for
62 option syntax is implemented for backward compatibility, but
63 is not documented here.)
67 utility examines files
69 and determines which files
72 are copied to the given disk, tape or other
73 storage medium for safe keeping (see the
75 option below for doing remote backups).
76 A dump that is larger than the output medium is broken into
78 On most media the size is determined by writing until an
79 end-of-media indication is returned.
85 On media that cannot reliably return an end-of-media indication
86 (such as some cartridge tape drives)
87 each volume is of a fixed size;
88 the actual size is determined by the tape size and density and/or
91 By default, the same output file name is used for each volume
92 after prompting the operator to change media.
94 The file system to be dumped is specified by the argument
96 as either its device-special file or its mount point
97 (if that is in a standard entry in
100 The following options are supported by
105 A level 0, full backup,
106 guarantees the entire file system is copied
110 A level number above 0,
113 copy all files new or modified since the
114 last dump of any lower level.
115 The default level is 0.
118 Bypass all tape length considerations, and enforce writing
119 until an end-of-media indication is returned.
120 This fits best for most modern tape drives.
121 Use of this option is particularly
122 recommended when appending to an existing tape, or using a tape
123 drive with hardware compression (where you can never be sure about
124 the compression ratio).
126 The number of kilobytes per output volume, except that if it is
127 not an integer multiple of the output block size,
128 the command uses the next smaller such multiple.
129 This option overrides the calculation of tape size
130 based on length and density.
131 .It Fl b Ar blocksize
132 The number of kilobytes per output block.
133 The default block size is 10.
134 .It Fl C Ar cachesize
135 Specify the cache size in megabytes.
136 This will greatly improve performance
139 possibly not noticing changes in the file system between passes.
141 recommended that you always use this option when dumping a snapshot.
144 forks, and the actual memory use may be larger than the specified cache
146 The recommended cache size is between 8 and 32 (megabytes).
148 Change the defaults for use with a cartridge tape drive, with a density
149 of 8000 bpi, and a length of 1700 feet.
150 .It Fl D Ar dumpdates
151 Specify an alternate path to the
159 The default is 1600BPI.
164 may be a special device file
169 (a floppy disk drive),
173 (the standard output).
174 Multiple file names may be given as a single argument separated by commas.
175 Each file will be used for one dump volume in the order listed;
176 if the dump requires more volumes than the number of names given,
177 the last file name will used for all remaining volumes after prompting
179 If the name of the file is of the form
184 writes to the named file on the remote host using
186 The default path name of the remote
189 .\" rmt path, is the path on the remote host
191 this can be overridden by the environment variable
193 .It Fl P Ar pipecommand
198 script string defined by
200 for the output device of each volume.
201 This child pipeline's
204 is redirected from the
206 output stream, and the environment variable
208 is set to the current volume number being written.
209 After every volume, the writer side of the pipe is closed and
212 Subject to the media size specified by
214 each volume is written in this manner as if the output were a tape drive.
220 only for dumps at or above the given
222 The default honor level is 1,
223 so that incremental backups omit such files
224 but full backups retain them.
226 This option is to notify
228 that it is dumping a live file system.
229 To obtain a consistent dump image,
231 takes a snapshot of the file system in the
233 directory in the root of the file system being dumped and
234 then does a dump of the snapshot.
235 The snapshot is removed when the dump is complete.
236 This option is ignored for unmounted or read-only file systems.
239 directory does not exist in the root of the file system being dumped,
240 a warning will be issued and the
242 will revert to the standard behavior.
243 This problem can be corrected by creating a
245 directory in the root of the file system to be dumped;
250 and its mode should be
255 requires operator attention,
256 notify all operators in the group
258 by means similar to a
261 Display an estimate of the backup size and the number of
262 tapes required, and exit without actually performing the dump.
264 Attempt to calculate the amount of tape needed
265 at a particular density.
266 If this amount is exceeded,
268 prompts for a new tape.
269 It is recommended to be a bit conservative on this option.
270 The default tape length is 2300 feet.
272 Use the specified date as the starting time for the dump
273 instead of the time determined from looking in
274 a warning will be issued and the
277 The format of date is the same as that of
279 This option is useful for automated dump scripts that wish to
280 dump over a specific period of time.
283 option is mutually exclusive from the
290 after a successful dump.
295 is readable by people, consisting of one
296 free format record per line:
302 There may be only one entry per file system at each level.
306 may be edited to change any of the fields,
308 The default path for the
314 option may be used to change it.
316 Tell the operator what file systems need to be dumped.
317 This information is gleaned from the files
325 to print out, for each file system in
329 the most recent dump date and level,
330 and highlights those file systems that should be dumped.
333 option is set, all other options are ignored, and
339 but prints only those file systems which need to be dumped.
342 Directories and regular files which have their
346 set will be omitted along with everything under such directories,
353 utility requires operator intervention on these conditions:
358 disk read error (if there are more than a threshold of 32).
359 In addition to alerting all operators implied by the
363 interacts with the operator on
365 control terminal at times when
367 can no longer proceed,
368 or if something is grossly wrong.
373 be answered by typing
379 Since making a dump involves a lot of time and effort for full dumps,
381 checkpoints itself at the start of each tape volume.
382 If writing that volume fails for some reason,
385 with operator permission,
386 restart itself from the checkpoint
387 after the old tape has been rewound and removed,
388 and a new tape has been mounted.
392 utility tells the operator what is going on at periodic intervals
393 (every 5 minutes, or promptly after receiving
395 including usually low estimates of the number of blocks to write,
396 the number of tapes it will take, the time to completion, and
397 the time to the tape change.
398 The output is verbose,
399 so that others know that the terminal
403 and will be for some time.
405 In the event of a catastrophic disk event, the time required
406 to restore all the necessary backup tapes or files to disk
407 can be kept to a minimum by staggering the incremental dumps.
408 An efficient method of staggering incremental dumps
409 to minimize the number of tapes follows:
410 .Bl -bullet -offset indent
412 Always start with a level 0 backup, for example:
413 .Bd -literal -offset indent
414 /sbin/dump -0u -f /dev/nsa0 /usr/src
417 This should be done at set intervals, say once a month or once every two months,
418 and on a set of fresh tapes that is saved forever.
420 After a level 0, dumps of active file systems (file systems with files
421 that change, depending on your partition layout some file systems may
422 contain only data that does not change) are taken on a daily basis,
423 using a modified Tower of Hanoi algorithm,
424 with this sequence of dump levels:
425 .Bd -literal -offset indent
426 3 2 5 4 7 6 9 8 9 9 ...
429 For the daily dumps, it should be possible to use a fixed number of tapes
430 for each day, used on a weekly basis.
431 Each week, a level 1 dump is taken, and
432 the daily Hanoi sequence repeats beginning with 3.
433 For weekly dumps, another fixed set of tapes per dumped file system is
434 used, also on a cyclical basis.
437 After several months or so, the daily and weekly tapes should get
438 rotated out of the dump cycle and fresh tapes brought in.
440 .Bl -tag -width ".Ev TAPE"
442 Device from which to read backup.
444 Pathname of the remote
448 Pathname of a remote shell program, if not
452 .Bl -tag -width /etc/dumpdates -compact
454 default tape unit to dump to
455 .It Pa /etc/dumpdates
457 (this can be changed;
462 dump table: file systems and frequency
468 Dump exits with zero status on success.
469 Startup errors are indicated with an exit code of 1;
470 abnormal termination is indicated with an exit code of 3.
484 Fewer than 32 read errors on the file system are ignored, though all
485 errors will generate a warning message.
486 This is a bit of a compromise.
487 In practice, it is possible to generate read errors when doing dumps
488 on mounted partitions if the file system is being modified while the
491 Since dumps are often done in an unattended fashion using
493 jobs asking for Operator intervention would result in the
496 However, there is nothing wrong with a dump tape written when this sort
497 of read error occurs, and there is no reason to terminate the
500 Each reel requires a new process, so parent processes for
501 reels already written just hang around until the entire tape
510 options does not report file systems that have never been recorded
519 knew about the dump sequence,
520 kept track of the tapes scribbled on,
521 told the operator which tape to mount when,
522 and provided more assistance
523 for the operator running
528 utility cannot do remote backups without being run as root, due to its
530 This will be fixed in a later version of
532 Presently, it works if you set it setuid (like it used to be), but this
533 might constitute a security risk.