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29 .\" @(#)dump.8 8.3 (Berkeley) 5/1/95
30 .\" $FreeBSD: src/sbin/dump/dump.8,v 1.27.2.18 2003/02/23 19:58:23 trhodes Exp $
31 .\"
32 .Dd September 29, 2016
33 .Dt DUMP 8
34 .Os
35 .Sh NAME
36 .Nm dump ,
37 .Nm rdump
38 .Nd UFS file system backup
39 .Sh SYNOPSIS
40 .Nm
41 .Op Fl 0123456789acknSu
42 .Op Fl B Ar records
43 .Op Fl b Ar blocksize
44 .Op Fl D Ar dumpdates
45 .Op Fl C Ar cachesize
46 .Op Fl d Ar density
47 .Op Fl f Ar file
48 .Op Fl h Ar level
49 .Op Fl s Ar feet
50 .Op Fl T Ar date
51 .Ar filesystem
52 .Nm
53 .Fl W | Fl w
54 .Sh DESCRIPTION
55 The
56 .Nm
57 utility examines files
58 on a file system
59 and determines which files
60 need to be backed up.
61 These files
62 are copied to the given disk, tape or other
63 storage medium for safe keeping (see the
64 .Fl f
65 option below for doing remote backups).
66 A dump that is larger than the output medium is broken into
67 multiple volumes.
68 On most media the size is determined by writing until an
69 end-of-media indication is returned.
70 This can be enforced
71 by using the
72 .Fl a
73 option.
74 .Pp
75 On media that cannot reliably return an end-of-media indication
76 (such as some cartridge tape drives)
77 each volume is of a fixed size;
78 the actual size is determined by the tape size and density and/or
79 .Fl B
80 options.
81 By default, the same output file name is used for each volume
82 after prompting the operator to change media.
83 .Pp
84 The file system to be dumped is specified by the argument
85 .Ar filesystem
86 as either its device-special file or its mount point
87 (if that is in a standard entry in
88 .Pa /etc/fstab ) .
89 .Pp
90 .Nm
91 may also be invoked as
92 .Nm rdump .
93 The
94 .Bx 4.3
95 option syntax is implemented for backward compatibility, but
96 is not documented here.
97 .Pp
98 The following options are supported by
99 .Nm :
100 .Bl -tag -width Ds
101 .It Fl 0-9
102 Dump levels.
103 A level 0, full backup,
104 guarantees the entire file system is copied
105 (but see also the
106 .Fl h
107 option below).
108 A level number above 0,
109 incremental backup,
110 tells dump to
111 copy all files new or modified since the
112 last dump of any lower level.
113 The default level is 0.
114 .It Fl a
115 .Dq auto-size .
116 Bypass all tape length considerations, and enforce writing
117 until an end-of-media indication is returned.
118 This fits best for most modern tape drives.
119 Use of this option is particularly
120 recommended when appending to an existing tape, or using a tape
121 drive with hardware compression (where you can never be sure about
122 the compression ratio).
123 .It Fl B Ar records
124 The number of kilobytes per output volume, except that if it is
125 not an integer multiple of the output block size,
126 the command uses the next smaller such multiple.
127 This option overrides the calculation of tape size
128 based on length and density.
129 .It Fl b Ar blocksize
130 The number of kilobytes per output block, except that if it is
131 larger than 64, the command uses 64. (See the BUGS section.)
132 The default block size is 10.
133 .It Fl c
134 Change the defaults for use with a cartridge tape drive, with a density
135 of 8000 bpi, and a length of 1700 feet.
136 .It Fl D Ar dumpdates
137 Specify an alternate path to the
138 .Pa dumpdates
139 file.
140 The default is
141 .Pa /etc/dumpdates .
142 .It Fl C Ar cachesize
143 Specify the cache size in megabytes. This will greatly improve performance
144 at the cost of
145 .Nm
146 possibly not noticing changes in the filesystem between passes.
147 Beware that
148 .Nm
149 forks, and the actual memory use may be larger than the specified cache
150 size. The recommended cache size is between 8 and 32 (megabytes).
151 .It Fl d Ar density
152 Set tape density to
153 .Ar density .
154 The default is 1600BPI.
155 .It Fl f Ar file
156 Write the backup to
157 .Ar file ;
158 .Ar file
159 may be a special device file
160 like
161 .Pa /dev/sa0
162 (a tape drive),
163 .Pa /dev/fd1
164 (a floppy disk drive),
165 an ordinary file,
166 or
167 .Sq Fl
168 (the standard output).
169 Multiple file names may be given as a single argument separated by commas.
170 Each file will be used for one dump volume in the order listed;
171 if the dump requires more volumes than the number of names given,
172 the last file name will used for all remaining volumes after prompting
173 for media changes.
174 If the name of the file is of the form
175 .Dq host:file ,
176 or
177 .Dq user@host:file ,
178 .Nm
179 writes to the named file on the remote host using
180 .Xr rmt 8 .
181 The default path name of the remote
182 .Xr rmt 8
183 program is
184 .\" rmt path, is the path on the remote host
185 .Pa /etc/rmt ;
186 this can be overridden by the environment variable
187 .Ev RMT .
188 .It Fl h Ar level
189 Honor the user
190 .Dq nodump
191 flag
192 .Pq Dv UF_NODUMP
193 only for dumps at or above the given
194 .Ar level .
195 The default honor level is 1,
196 so that incremental backups omit such files
197 but full backups retain them.
198 .It Fl k
199 Use Kerberos authentication to talk to remote tape servers. (Only
200 available if this option was enabled when
201 .Nm
202 was compiled.)
203 .It Fl n
204 Whenever
205 .Nm
206 requires operator attention,
207 notify all operators in the group
208 .Dq operator
209 by means similar to a
210 .Xr wall 1 .
211 .It Fl s Ar feet
212 Attempt to calculate the amount of tape needed
213 at a particular density.
214 If this amount is exceeded,
215 .Nm
216 prompts for a new tape.
217 It is recommended to be a bit conservative on this option.
218 The default tape length is 2300 feet.
219 .It Fl S
220 Display an estimate of the backup size and the number of
221 tapes required, and exit without actually performing the dump.
222 .It Fl T Ar date
223 Use the specified date as the starting time for the dump
224 instead of the time determined from looking in
225 the
226 .Pa dumpdates
227 file.
228 The format of date is the same as that of
229 .Xr ctime 3 .
230 This option is useful for automated dump scripts that wish to
231 dump over a specific period of time.
232 The
233 .Fl T
234 option is mutually exclusive from the
235 .Fl u
236 option.
237 .It Fl u
238 Update the
239 .Pa dumpdates
240 file
241 after a successful dump.
242 The format of
243 the
244 .Pa dumpdates
245 file
246 is readable by people, consisting of one
247 free format record per line:
248 file system name,
249 increment level
250 and
251 .Xr ctime 3
252 format dump date.
253 There may be only one entry per file system at each level.
254 The
255 .Pa dumpdates
256 file
257 may be edited to change any of the fields,
258 if necessary.
259 The default path for the
260 .Pa dumpdates
261 file is
262 .Pa /etc/dumpdates ,
263 but the
264 .Fl D
265 option may be used to change it.
266 .It Fl W
267 Tell the operator what file systems need to be dumped.
268 This information is gleaned from the files
269 .Pa dumpdates
270 and
271 .Pa /etc/fstab .
272 The
273 .Fl W
274 option causes
275 .Nm
276 to print out, for each file system in
277 the
278 .Pa dumpdates
279 file
280 the most recent dump date and level,
281 and highlights those file systems that should be dumped.
282 If the
283 .Fl W
284 option is set, all other options are ignored, and
285 .Nm
286 exits immediately.
287 .It Fl w
288 Is like
289 .Fl W ,
290 but prints only those file systems which need to be dumped.
291 .El
292 .Pp
293 Directories and regular files which have their
294 .Dq nodump
295 flag
296 .Pq Dv UF_NODUMP
297 set will be omitted along with everything under such directories,
298 subject to the
299 .Fl h
300 option.
301 .Pp
302 The
303 .Nm
304 utility requires operator intervention on these conditions:
305 end of tape,
306 end of dump,
307 tape write error,
308 tape open error or
309 disk read error (if there are more than a threshold of 32).
310 In addition to alerting all operators implied by the
311 .Fl n
312 key,
313 .Nm
314 interacts with the operator on
315 .Em dump's
316 control terminal at times when
317 .Nm
318 can no longer proceed,
319 or if something is grossly wrong.
320 All questions
321 .Nm
322 poses
323 .Em must
324 be answered by typing
325 .Dq yes
326 or
327 .Dq no ,
328 appropriately.
329 .Pp
330 Since making a dump involves a lot of time and effort for full dumps,
331 .Nm
332 checkpoints itself at the start of each tape volume.
333 If writing that volume fails for some reason,
334 .Nm
335 will,
336 with operator permission,
337 restart itself from the checkpoint
338 after the old tape has been rewound and removed,
339 and a new tape has been mounted.
340 .Pp
341 The
342 .Nm
343 utility tells the operator what is going on at periodic intervals
344 (every 5 minutes, or promptly after receiving
345 .Dv SIGINFO ) ,
346 including usually low estimates of the number of blocks to write,
347 the number of tapes it will take, the time to completion, and
348 the time to the tape change.
349 The output is verbose,
350 so that others know that the terminal
351 controlling
352 .Nm
353 is busy,
354 and will be for some time.
355 .Pp
356 In the event of a catastrophic disk event, the time required
357 to restore all the necessary backup tapes or files to disk
358 can be kept to a minimum by staggering the incremental dumps.
359 An efficient method of staggering incremental dumps
360 to minimize the number of tapes follows:
361 .Bl -bullet -offset indent
362 .It
363 Always start with a level 0 backup, for example:
364 .Bd -literal -offset indent
365 /sbin/dump -0u -f /dev/nsa0 /usr/src
366 .Ed
367 .Pp
368 This should be done at set intervals, say once a month or once every two months,
369 and on a set of fresh tapes that is saved forever.
370 .It
371 After a level 0, dumps of active file systems are taken on a daily basis,
372 using a modified Tower of Hanoi algorithm,
373 with this sequence of dump levels:
374 .Bd -literal -offset indent
375 3 2 5 4 7 6 9 8 9 9 ...
376 .Ed
377 .Pp
378 For the daily dumps, it should be possible to use a fixed number of tapes
379 for each day, used on a weekly basis.
380 Each week, a level 1 dump is taken, and
381 the daily Hanoi sequence repeats beginning with 3.
382 For weekly dumps, another fixed set of tapes per dumped file system is
383 used, also on a cyclical basis.
384 .El
385 .Pp
386 After several months or so, the daily and weekly tapes should get
387 rotated out of the dump cycle and fresh tapes brought in.
388 .Sh ENVIRONMENT
389 .Bl -tag -width ".Ev TAPE"
390 .It Ev TAPE
391 Device from which to read backup.
392 .It Ev RMT
393 Pathname of the remote
394 .Xr rmt 8
395 program.
396 .El
397 .Sh FILES
398 .Bl -tag -width /etc/dumpdates -compact
399 .It Pa /dev/sa0
400 default tape unit to dump to
401 .It Pa /etc/dumpdates
402 dump date records
403 (this can be changed;
404 see the
405 .Fl D
406 option)
407 .It Pa /etc/fstab
408 dump table: file systems and frequency
409 .It Pa /etc/group
410 to find group
411 .Em operator
412 .El
413 .Sh EXIT STATUS
414 Dump exits with zero status on success.
415 Startup errors are indicated with an exit code of 1;
416 abnormal termination is indicated with an exit code of 3.
417 .Sh DIAGNOSTICS
418 Many, and verbose.
419 .Sh SEE ALSO
420 .Xr chflags 1 ,
421 .Xr fstab 5 ,
422 .Xr UFS 5 ,
423 .Xr restore 8 ,
424 .Xr rmt 8
425 .Sh HISTORY
426 A
427 .Nm
428 utility appeared in
429 .At v4 .
430 .Sh BUGS
431 Fewer than 32 read errors on the file system are ignored.
432 .Pp
433 Each reel requires a new process, so parent processes for
434 reels already written just hang around until the entire tape
435 is written.
436 .Pp
437 Currently,
438 .Xr physio 9
439 slices all requests into chunks of 64 KB.
440 Therefore, it is
441 impossible to use a larger output block size, so
442 .Nm
443 will prevent this from happening.
444 .Pp
445 The
446 .Nm
447 utility with the
448 .Fl W
449 or
450 .Fl w
451 options does not report file systems that have never been recorded
452 in the
453 .Pa dumpdates
454 file,
455 even if listed in
456 .Pa /etc/fstab .
457 .Pp
458 It would be nice if
459 .Nm
460 knew about the dump sequence,
461 kept track of the tapes scribbled on,
462 told the operator which tape to mount when,
463 and provided more assistance
464 for the operator running
465 .Xr restore 8 .
466 .Pp
467 The
468 .Nm
469 utility cannot do remote backups without being run as root, due to its
470 security history.
471 This may be fixed in a later version of
472 .Dx .
473 Presently, it works if you set it setuid (like it used to be), but this
474 might constitute a security risk.