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33 .\" @(#)dump.8 8.3 (Berkeley) 5/1/95
34 .\" $FreeBSD: src/sbin/dump/dump.8,v 1.27.2.18 2003/02/23 19:58:23 trhodes Exp $
35 .\" $DragonFly: src/sbin/dump/dump.8,v 1.6 2008/10/16 23:08:30 swildner Exp $
36 .\"
37 .Dd March 1, 2002
38 .Dt DUMP 8
39 .Os
40 .Sh NAME
41 .Nm dump ,
42 .Nm rdump
43 .Nd file system backup
44 .Sh SYNOPSIS
45 .Nm
46 .Op Fl 0123456789acknSu
47 .Op Fl B Ar records
48 .Op Fl b Ar blocksize
49 .Op Fl D Ar dumpdates
50 .Op Fl C Ar cachesize
51 .Op Fl d Ar density
52 .Op Fl f Ar file
53 .Op Fl h Ar level
54 .Op Fl s Ar feet
55 .Op Fl T Ar date
56 .Ar file system
57 .Nm
58 .Fl W | Fl w
59 .Pp
60 .Nm rdump
61 is an alternate name for
62 .Nm .
63 .Pp
64 .in \" XXX
65 (The
66 .Bx 4.3
67 option syntax is implemented for backward compatibility, but
68 is not documented here.)
69 .Sh DESCRIPTION
70 The
71 .Nm
72 utility examines files
73 on a file system
74 and determines which files
75 need to be backed up.
76 These files
77 are copied to the given disk, tape or other
78 storage medium for safe keeping (see the
79 .Fl f
80 option below for doing remote backups).
81 A dump that is larger than the output medium is broken into
82 multiple volumes.
83 On most media the size is determined by writing until an
84 end-of-media indication is returned.
85 This can be enforced
86 by using the
87 .Fl a
88 option.
89 .Pp
90 On media that cannot reliably return an end-of-media indication
91 (such as some cartridge tape drives)
92 each volume is of a fixed size;
93 the actual size is determined by the tape size and density and/or
94 .Fl B
95 options.
96 By default, the same output file name is used for each volume
97 after prompting the operator to change media.
98 .Pp
99 The file system to be dumped is specified by the argument
100 .Ar filesystem
101 as either its device-special file or its mount point
102 (if that is in a standard entry in
103 .Pa /etc/fstab ) .
104 .Pp
105 The following options are supported by
106 .Nm :
107 .Bl -tag -width Ds
108 .It Fl 0-9
109 Dump levels.
110 A level 0, full backup,
111 guarantees the entire file system is copied
112 (but see also the
113 .Fl h
114 option below).
115 A level number above 0,
116 incremental backup,
117 tells dump to
118 copy all files new or modified since the
119 last dump of any lower level.
120 The default level is 0.
121 .It Fl a
122 .Dq auto-size .
123 Bypass all tape length considerations, and enforce writing
124 until an end-of-media indication is returned.
125 This fits best for most modern tape drives.
126 Use of this option is particularly
127 recommended when appending to an existing tape, or using a tape
128 drive with hardware compression (where you can never be sure about
129 the compression ratio).
130 .It Fl B Ar records
131 The number of kilobytes per output volume, except that if it is
132 not an integer multiple of the output block size,
133 the command uses the next smaller such multiple.
134 This option overrides the calculation of tape size
135 based on length and density.
136 .It Fl b Ar blocksize
137 The number of kilobytes per output block, except that if it is
138 larger than 64, the command uses 64. (See the BUGS section.)
139 The default block size is 10.
140 .It Fl c
141 Change the defaults for use with a cartridge tape drive, with a density
142 of 8000 bpi, and a length of 1700 feet.
143 .It Fl D Ar dumpdates
144 Specify an alternate path to the
145 .Pa dumpdates
146 file.
147 The default is
148 .Pa /etc/dumpdates .
149 .It Fl C Ar cachesize
150 Specify the cache size in megabytes. This will greatly improve performance
151 at the cost of
152 .Nm
153 possibly not noticing changes in the filesystem between passes.
154 Beware that
155 .Nm
156 forks, and the actual memory use may be larger than the specified cache
157 size. The recommended cache size is between 8 and 32 (megabytes).
158 .It Fl d Ar density
159 Set tape density to
160 .Ar density .
161 The default is 1600BPI.
162 .It Fl f Ar file
163 Write the backup to
164 .Ar file ;
165 .Ar file
166 may be a special device file
167 like
168 .Pa /dev/sa0
169 (a tape drive),
170 .Pa /dev/fd1
171 (a floppy disk drive),
172 an ordinary file,
173 or
174 .Sq Fl
175 (the standard output).
176 Multiple file names may be given as a single argument separated by commas.
177 Each file will be used for one dump volume in the order listed;
178 if the dump requires more volumes than the number of names given,
179 the last file name will used for all remaining volumes after prompting
180 for media changes.
181 If the name of the file is of the form
182 .Dq host:file ,
183 or
184 .Dq user@host:file ,
185 .Nm
186 writes to the named file on the remote host using
187 .Xr rmt 8 .
188 The default path name of the remote
189 .Xr rmt 8
190 program is
191 .\" rmt path, is the path on the remote host
192 .Pa /etc/rmt ;
193 this can be overridden by the environment variable
194 .Ev RMT .
195 .It Fl h Ar level
196 Honor the user
197 .Dq nodump
198 flag
199 .Pq Dv UF_NODUMP
200 only for dumps at or above the given
201 .Ar level .
202 The default honor level is 1,
203 so that incremental backups omit such files
204 but full backups retain them.
205 .It Fl k
206 Use Kerberos authentication to talk to remote tape servers. (Only
207 available if this option was enabled when
208 .Nm
209 was compiled.)
210 .It Fl n
211 Whenever
212 .Nm
213 requires operator attention,
214 notify all operators in the group
215 .Dq operator
216 by means similar to a
217 .Xr wall 1 .
218 .It Fl s Ar feet
219 Attempt to calculate the amount of tape needed
220 at a particular density.
221 If this amount is exceeded,
222 .Nm
223 prompts for a new tape.
224 It is recommended to be a bit conservative on this option.
225 The default tape length is 2300 feet.
226 .It Fl S
227 Display an estimate of the backup size and the number of
228 tapes required, and exit without actually performing the dump.
229 .It Fl T Ar date
230 Use the specified date as the starting time for the dump
231 instead of the time determined from looking in
232 the
233 .Pa dumpdates
234 file.
235 The format of date is the same as that of
236 .Xr ctime 3 .
237 This option is useful for automated dump scripts that wish to
238 dump over a specific period of time.
239 The
240 .Fl T
241 option is mutually exclusive from the
242 .Fl u
243 option.
244 .It Fl u
245 Update the
246 .Pa dumpdates
247 file
248 after a successful dump.
249 The format of
250 the
251 .Pa dumpdates
252 file
253 is readable by people, consisting of one
254 free format record per line:
255 file system name,
256 increment level
257 and
258 .Xr ctime 3
259 format dump date.
260 There may be only one entry per file system at each level.
261 The
262 .Pa dumpdates
263 file
264 may be edited to change any of the fields,
265 if necessary.
266 The default path for the
267 .Pa dumpdates
268 file is
269 .Pa /etc/dumpdates ,
270 but the
271 .Fl D
272 option may be used to change it.
273 .It Fl W
274 Tell the operator what file systems need to be dumped.
275 This information is gleaned from the files
276 .Pa dumpdates
277 and
278 .Pa /etc/fstab .
279 The
280 .Fl W
281 option causes
282 .Nm
283 to print out, for each file system in
284 the
285 .Pa dumpdates
286 file
287 the most recent dump date and level,
288 and highlights those file systems that should be dumped.
289 If the
290 .Fl W
291 option is set, all other options are ignored, and
292 .Nm
293 exits immediately.
294 .It Fl w
295 Is like
296 .Fl W ,
297 but prints only those file systems which need to be dumped.
298 .El
299 .Pp
300 Directories and regular files which have their
301 .Dq nodump
302 flag
303 .Pq Dv UF_NODUMP
304 set will be omitted along with everything under such directories,
305 subject to the
306 .Fl h
307 option.
308 .Pp
309 The
310 .Nm
311 utility requires operator intervention on these conditions:
312 end of tape,
313 end of dump,
314 tape write error,
315 tape open error or
316 disk read error (if there are more than a threshold of 32).
317 In addition to alerting all operators implied by the
318 .Fl n
319 key,
320 .Nm
321 interacts with the operator on
322 .Em dump's
323 control terminal at times when
324 .Nm
325 can no longer proceed,
326 or if something is grossly wrong.
327 All questions
328 .Nm
329 poses
330 .Em must
331 be answered by typing
332 .Dq yes
333 or
334 .Dq no ,
335 appropriately.
336 .Pp
337 Since making a dump involves a lot of time and effort for full dumps,
338 .Nm
339 checkpoints itself at the start of each tape volume.
340 If writing that volume fails for some reason,
341 .Nm
342 will,
343 with operator permission,
344 restart itself from the checkpoint
345 after the old tape has been rewound and removed,
346 and a new tape has been mounted.
347 .Pp
348 The
349 .Nm
350 utility tells the operator what is going on at periodic intervals
351 (every 5 minutes, or promptly after receiving
352 .Dv SIGINFO ) ,
353 including usually low estimates of the number of blocks to write,
354 the number of tapes it will take, the time to completion, and
355 the time to the tape change.
356 The output is verbose,
357 so that others know that the terminal
358 controlling
359 .Nm
360 is busy,
361 and will be for some time.
362 .Pp
363 In the event of a catastrophic disk event, the time required
364 to restore all the necessary backup tapes or files to disk
365 can be kept to a minimum by staggering the incremental dumps.
366 An efficient method of staggering incremental dumps
367 to minimize the number of tapes follows:
368 .Bl -bullet -offset indent
369 .It
370 Always start with a level 0 backup, for example:
371 .Bd -literal -offset indent
372 /sbin/dump -0u -f /dev/nsa0 /usr/src
373 .Ed
374 .Pp
375 This should be done at set intervals, say once a month or once every two months,
376 and on a set of fresh tapes that is saved forever.
377 .It
378 After a level 0, dumps of active file systems are taken on a daily basis,
379 using a modified Tower of Hanoi algorithm,
380 with this sequence of dump levels:
381 .Bd -literal -offset indent
382 3 2 5 4 7 6 9 8 9 9 ...
383 .Ed
384 .Pp
385 For the daily dumps, it should be possible to use a fixed number of tapes
386 for each day, used on a weekly basis.
387 Each week, a level 1 dump is taken, and
388 the daily Hanoi sequence repeats beginning with 3.
389 For weekly dumps, another fixed set of tapes per dumped file system is
390 used, also on a cyclical basis.
391 .El
392 .Pp
393 After several months or so, the daily and weekly tapes should get
394 rotated out of the dump cycle and fresh tapes brought in.
395 .Sh ENVIRONMENT
396 .Bl -tag -width ".Ev TAPE"
397 .It Ev TAPE
398 Device from which to read backup.
399 .It Ev RMT
400 Pathname of the remote
401 .Xr rmt 8
402 program.
403 .El
404 .Sh FILES
405 .Bl -tag -width /etc/dumpdates -compact
406 .It Pa /dev/sa0
407 default tape unit to dump to
408 .It Pa /etc/dumpdates
409 dump date records
410 (this can be changed;
411 see the
412 .Fl D
413 option)
414 .It Pa /etc/fstab
415 dump table: file systems and frequency
416 .It Pa /etc/group
417 to find group
418 .Em operator
419 .El
420 .Sh DIAGNOSTICS
421 Many, and verbose.
422 .Pp
423 Dump exits with zero status on success.
424 Startup errors are indicated with an exit code of 1;
425 abnormal termination is indicated with an exit code of 3.
426 .Sh SEE ALSO
427 .Xr chflags 1 ,
428 .Xr fstab 5 ,
429 .Xr restore 8 ,
430 .Xr rmt 8
431 .Sh HISTORY
432 A
433 .Nm
434 utility appeared in
435 .At v6 .
436 .Sh BUGS
437 Fewer than 32 read errors on the file system are ignored.
438 .Pp
439 Each reel requires a new process, so parent processes for
440 reels already written just hang around until the entire tape
441 is written.
442 .Pp
443 Currently,
444 .Xr physio 9
445 slices all requests into chunks of 64 KB.
446 Therefore, it is
447 impossible to use a larger output block size, so
448 .Nm
449 will prevent this from happening.
450 .Pp
451 The
452 .Nm
453 utility with the
454 .Fl W
455 or
456 .Fl w
457 options does not report file systems that have never been recorded
458 in the
459 .Pa dumpdates
460 file,
461 even if listed in
462 .Pa /etc/fstab .
463 .Pp
464 It would be nice if
465 .Nm
466 knew about the dump sequence,
467 kept track of the tapes scribbled on,
468 told the operator which tape to mount when,
469 and provided more assistance
470 for the operator running
471 .Xr restore 8 .
472 .Pp
473 The
474 .Nm
475 utility cannot do remote backups without being run as root, due to its
476 security history.
477 This may be fixed in a later version of
478 .Dx .
479 Presently, it works if you set it setuid (like it used to be), but this
480 might constitute a security risk.