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29 .\" $Id: dump.8.in,v 1.61 2009/06/18 09:36:52 stelian Exp $
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31 .TH DUMP 8 "version __VERSION__ of __DATE__" BSD "System management commands"
33 dump \- ext2/3 filesystem backup
35 .B dump
36 [\fB\-\fIlevel#\fR]
37 [\fB\-ackMnqSuv]
38 [\fB\-A \fIfile\fR]
39 [\fB\-B \fIrecords\fR]
40 [\fB\-b \fIblocksize\fR]
41 [\fB\-d \fIdensity\fR]
42 [\fB\-D \fIfile\fR]
43 [\fB\-e \fIinode numbers\fR]
44 [\fB\-E \fIfile\fR]
45 [\fB\-f \fIfile\fR]
46 [\fB\-F \fIscript\fR]
47 [\fB\-h \fIlevel\fR]
48 [\fB\-I \fInr errors\fR]
49 [\fB\-j\fIcompression level\fR]
50 [\fB\-L \fIlabel\fR]
51 [\fB\-Q \fIfile\fR]
52 [\fB\-s \fIfeet\fR]
53 [\fB\-T \fIdate\fR]
54 [\fB\-y\fR]
55 [\fB\-z\fIcompression level\fR]
56 .I files-to-dump
57 .PP
58 .B dump
59 [\fB\-W \fR| \fB\-w\fR]
61 .B Dump
62 examines files on an ext2/3 filesystem and determines which files need to be
63 backed up. These files are copied to the given disk, tape or other storage
64 medium for safe keeping (see the
65 .B \-f
66 option below for doing remote backups). A dump that is larger than the output
67 medium is broken into multiple volumes. On most media the size is determined by
68 writing until an end-of-media indication is returned.
69 .PP
70 On media that cannot reliably return an end-of-media indication (such as some
71 cartridge tape drives), each volume is of a fixed size; the actual size is
72 determined by specifying cartridge media, or via the tape size, density and/or
73 block count options below. By default, the same output file name is used for
74 each volume after prompting the operator to change media.
75 .PP
76 .I files-to-dump
77 is either a mountpoint of a filesystem or a list of files and directories to be
78 backed up as a subset of a filesystem. In the former case, either the path to a
79 mounted filesystem or the device of an unmounted filesystem can be used. In the
80 latter case, certain restrictions are placed on the backup:
81 .B \-u
82 is not allowed, the only dump level that is supported is
83 .B 0
84 and all the files and directories must reside on the same filesystem.
86 The following options are supported by
87 .B dump:
88 .TP
89 .BI \-level#
90 The dump level (any integer). A level 0, full backup, specified by
91 .B \-0
92 guarantees the entire file system is copied (but see also the
93 .B \-h
94 option below). A level number above 0, incremental backup, tells
95 .B dump
96 to
97 copy all files new or modified since the last dump of a lower level. The
98 default level is 0. Historically only levels 0 to 9 were usable in
99 dump, this version is able to understand any integer as a dump level.
100 .TP
101 .BI \-a
102 \*(lqauto-size\*(rq. Bypass all tape length calculations, and write until an
103 end-of-media indication is returned. This works best for most modern tape
104 drives, and is the default. Use of this option is particularly recommended when
105 appending to an existing tape, or using a tape drive with hardware compression
106 (where you can never be sure about the compression ratio).
107 .TP
108 .BI \-A " archive_file"
109 Archive a dump table-of-contents in the specified
110 .I archive_file
111 to be used by
112 .BR restore (8)
113 to determine whether a file is in the dump file that is being restored.
114 .TP
115 .BI \-b " blocksize"
116 The number of kilobytes per dump record. The default blocksize is 10,
117 unless the
118 .B \-d
119 option has been used to specify a tape density of 6250BPI or more,
120 in which case the default blocksize is 32. Th maximal value is 1024.
121 Note however that, since the IO system slices all requests into chunks
122 of
124 (which can be as low as 64kB), you can experience problems with
125 .BR dump (8)
126 and
127 .BR restore (8)
128 when using a higher value, depending on your kernel and/or libC versions.
129 .TP
130 .BI \-B " records"
131 The number of 1 kB blocks per volume. Not normally required, as
132 .B dump
133 can detect end-of-media. When the specified size is reached,
134 .B dump
135 waits for you to change the volume. This option overrides the calculation of
136 tape size based on length and density. If compression is on this limits the
137 size of the compressed output per volume. Multiple values may be given
138 as a single argument separated by commas. Each value will be used for one
139 dump volume in the order listed; if
140 .B dump
141 creates more volumes than the
142 number of values given, the last value will be used for the remaining
143 volumes. This is useful for filling up already partially filled media
144 (and then continuing with full size volumes on empty media) or mixing media
145 of different sizes.
146 .TP
147 .BI \-c
148 Change the defaults for use with a cartridge tape drive, with a density of 8000
149 bpi, and a length of 1700 feet. Specifying a cartridge drive overrides the
150 end-of-media detection.
151 .TP
152 .BI \-d " density"
153 Set tape density to
154 .IR density .
155 The default is 1600BPI. Specifying a tape density overrides the end-of-media
156 detection.
157 .TP
158 .BI \-D " file"
159 Set the path name of the file storing the information about the previous
160 full and incremental dumps. The default location is
161 .IR __DUMPDATES__ .
162 .TP
163 .BI \-e " inodes"
164 Exclude
165 .I inodes
166 from the dump. The
167 .I inodes
168 parameter is a comma separated list of inode numbers (you can use
169 .BR stat (1)
170 to find the inode number for a file or directory).
171 .TP
172 .BI \-E " file"
173 Read list of inodes to be excluded from the dump from the text file
174 .IR file .
175 The file
176 .I file
177 should be an ordinary file containing inode numbers separated by newlines.
178 .TP
179 .BI \-f " file"
180 Write the backup to
181 .IR file ;
182 .I file
183 may be a special device file like
184 .I /dev/st0
185 (a tape drive),
186 .I /dev/rsd1c
187 (a floppy disk drive), an ordinary file, or
188 .I \-
189 (the standard output). Multiple file names may be given as a single argument
190 separated by commas. Each file will be used for one dump volume in the order
191 listed; if the dump requires more volumes than the number of names given,
192 the last file name will used for all remaining volumes after prompting for
193 media changes. If the name of the file is of the form
194 .I host:file
195 or
196 .I user@host:file
197 .B dump
198 writes to the named file on the remote host (which should already
199 exist, dump doesn't create a new remote file) using
200 .BR rmt (8).
201 The default path name of the remote
202 .BR rmt (8)
203 program is
204 .IR /etc/rmt ;
205 this can be overridden by the environment variable
206 .BR RMT .
207 .TP
208 .BI \-F " script"
209 Run script at the end of each tape (except for the last one).
210 The device name and the current volume number are passed on the
211 command line. The script must return 0 if
212 .B dump
213 should continue without asking the user to change the tape, 1 if
214 .B dump
215 should continue but ask the user to change the tape. Any other exit code will
216 cause
217 .B dump
218 to abort. For security reasons,
219 .B dump
220 reverts back to the real user ID and the real group ID before running the
221 script.
222 .TP
223 .BI \-h " level"
224 Honor the user
225 .B nodump
226 flag
228 only for dumps at or above the given
229 .IR level .
230 The default honor level is 1, so that incremental backups omit such files but
231 full backups retain them.
232 .TP
233 .BI \-I " nr errors"
234 By default,
235 .B dump
236 will ignore the first 32 read errors on the file system before asking for
237 operator intervention. You can change this using this flag to any value. This
238 is useful when running
239 .B dump
240 on an active filesystem where read errors simply indicate an inconsistency
241 between the mapping and dumping passes.
242 .IP
243 A value of 0 means that all read errors will be ignored.
244 .TP
245 .BI \-j "compression level"
246 Compress every block to be written on the tape using bzlib library. This option
247 will work only when dumping to a file or pipe or, when dumping to a tape drive,
248 if the tape drive is capable of writing variable length blocks. You will need
249 at least the 0.4b24 version of
250 .B restore
251 in order to extract compressed tapes. Tapes written using compression will not
252 be compatible with the BSD tape format. The (optional) parameter specifies the
253 compression level bzlib will use. The default compression level is 2. If the
254 optional parameter is specified, there should be no white space between the
255 option letter and the parameter.
256 .TP
257 .BI \-k
258 Use Kerberos authentication to talk to remote tape servers. (Only available if
259 this option was enabled when
260 .B dump
261 was compiled.)
262 .TP
263 .BI \-L " label"
264 The user-supplied text string
265 .I label
266 is placed into the dump header, where tools like
267 .BR restore (8)
268 and
269 .BR file (8)
270 can access it. Note that this label is limited to be at most
272 (currently 16) characters, which must include the terminating \e0.
273 .TP
274 .BI \-m
275 If this flag is specified,
276 .B dump
277 will optimise the output for inodes having been changed but not modified since
278 the last dump ('changed' and 'modified' have the meaning defined in
279 .BR stat (2)
280 ). For those inodes,
281 .B dump
282 will save only the metadata, instead of saving the entire inode contents.
283 Inodes which are either directories or have been modified since the last dump
284 are saved in a regular way. Uses of this flag must be consistent, meaning that
285 either every dump in an incremental dump set have the flag, or no one has it.
286 .IP
287 If you use this option, be aware that many programs that unpack
288 files from archives (e.g. tar, rpm, unzip, dpkg) may set files'
289 mtimes to dates in the past. Files installed in this way may not be
290 dumped correctly using "dump -m" if the modified mtime is earlier
291 than the previous level dump.
292 .IP
293 Tapes written using such 'metadata only' inodes will not be compatible with the
294 BSD tape format or older versions of
295 .B restore.
296 .TP
297 .BI \-M
298 Enable the multi-volume feature. The name specified with
299 .B f
300 is treated as a prefix and
301 .B dump
302 writes in sequence to
303 .I <prefix>001, <prefix>002
304 etc. This can be useful when dumping to files on an ext2 partition, in order to
305 bypass the 2GB file size limitation.
306 .TP
307 .BI \-n
308 Whenever
309 .B dump
310 requires operator attention, notify all operators in the group
311 .B operator
312 by means similar to a
313 .BR wall (1).
314 .TP
315 .BI \-q
316 Make
317 .B dump
318 abort immediately whenever operator attention is required, without prompting in
319 case of write errors, tape changes etc.
320 .TP
321 .BI \-Q " file"
322 Enable the Quick File Access support. Tape positions for each inode are stored
323 into the file
324 .I file
325 which is used by
326 .B restore
327 (if called with parameter
328 .B \-Q
329 and the filename) to directly position the tape at the file
330 .B restore
331 is currently working on. This saves hours when restoring single files from
332 large backups, saves the tapes and the drive's head.
333 .IP
334 It is recommended to set up the st driver to return logical tape positions
335 rather than physical before calling
336 .B dump/restore
337 with parameter
338 .BR \-Q .
339 Since not all tape devices support physical tape positions those tape devices
340 return an error during
341 .B dump/restore
342 when the st driver is set to the default physical setting. Please see the
343 .BR st (4)
344 man page, option
346 , or the
347 .BR mt (1)
348 man page, on how to set the driver to return logical tape positions.
349 .IP
350 Before calling
351 .B restore
352 with parameter
353 .BR \-Q ,
354 always make sure the st driver is set to return the same type of tape position
355 used during the call to
356 .BR dump .
357 Otherwise
358 .B restore
359 may be confused.
360 .IP
361 This option can be used when dumping to local tapes (see above) or to local
362 files.
363 .TP
364 .BI \-s " feet"
365 Attempt to calculate the amount of tape needed at a particular density. If this
366 amount is exceeded,
367 .B dump
368 prompts for a new tape. It is recommended to be a bit conservative on this
369 option. The default tape length is 2300 feet. Specifying the tape size
370 overrides end-of-media detection.
371 .TP
372 .BI \-S
373 Size estimate. Determine the amount of space that is needed to perform the dump
374 without actually doing it, and display the estimated number of bytes it will
375 take. This is useful with incremental dumps to determine how many volumes of
376 media will be needed.
377 .TP
378 .BI \-T " date"
379 Use the specified date as the starting time for the dump instead of the time
380 determined from looking in
381 .I __DUMPDATES__ .
382 The format of
383 .I date
384 is the same as that of
385 .BR ctime (3)
386 followed by an rfc822 timezone specification: either a plus or minus sign
387 followed by two digits for the number of hours and two digits for the minutes.
388 For example, -0800 for eight hours west of Greenwich or +0230 for two hours
389 and a half east of Greenwich. This timezone offset takes into account
390 daylight savings time (if applicable to the timezone): UTC offsets
391 when daylight savings time is in effect will be different than offsets
392 when daylight savings time is not in effect. For backward
393 compatibility, if no timezone is specified, a local time is assumed.
394 This option is useful for automated dump scripts that wish to dump over a
395 specific period of time. The
396 .B \-T
397 option is mutually exclusive from the
398 .B \-u
399 option.
400 .TP
401 .BI \-u
402 Update the file
403 .I __DUMPDATES__
404 after a successful dump. The format of
405 .I __DUMPDATES__
406 is readable by people, consisting of one free format record per line:
407 filesystem name, increment level and
408 .BR ctime (3)
409 format dump date followed by a rfc822 timezone specification (see the
410 .B \-u
411 option for details). If no timezone offset is specified, times are interpreted
412 as local. Whenever the file is written, all dates in the file are converted
413 to the local time zone, without changing the UTC times. There
414 may be only one entry per filesystem at each level. The file
415 .I __DUMPDATES__
416 may be edited to change any of the fields, if necessary.
417 .TP
418 .BI \-v
419 The
420 .B \-v
421 (verbose) makes
422 .B dump
423 to print extra information which could be helpful in debug sessions.
424 .TP
425 .BI \-W
426 .B Dump
427 tells the operator what file systems need to be dumped. This information is
428 gleaned from the files
429 .I __DUMPDATES__
430 and
431 .IR /etc/fstab .
432 The
433 .B \-W
434 option causes
435 .B dump
436 to print out, for all file systems in
437 .I __DUMPDATES__ ,
438 and regognized file systems in
439 .I /etc/mtab
440 and
441 .IR /etc/fstab .
442 the most recent dump date and level, and highlights those that should be
443 dumped. If the
444 .B \-W
445 option is set, all other options are ignored, and
446 .B dump
447 exits immediately.
448 .TP
449 .BI \-w
450 Is like
451 .BR \-W ,
452 but prints only recognized filesystems in
453 .I /etc/mtab
454 and
455 .I /etc/fstab
456 which need to be dumped.
457 .TP
458 .BI \-y
459 Compress every block to be written to the tape using the lzo library.
460 This doesn't compress as well as the zlib library but it's much faster.
461 This option will work only when dumping to a file or pipe or, when dumping to
462 a tape drive, if the tape drive is capable of writing variable length blocks.
463 You will need at least the 0.4b34 version of
464 .B restore
465 in order to extract compressed tapes. Tapes written using compression will not
466 be compatible with the BSD tape format.
467 .TP
468 .BI \-z "compression level"
469 Compress every block to be written on the tape using zlib library. This option
470 will work only when dumping to a file or pipe or, when dumping to a tape drive,
471 if the tape drive is capable of writing variable length blocks. You will need
472 at least the 0.4b22 version of
473 .B restore
474 in order to extract compressed tapes. Tapes written using compression will not
475 be compatible with the BSD tape format. The (optional) parameter specifies the
476 compression level zlib will use. The default compression level is 2. If the
477 optional parameter is specified, there should be no white space between the
478 option letter and the parameter.
479 .PP
480 .B Dump
481 requires operator intervention on these conditions: end of tape, end of dump,
482 tape write error, tape open error or disk read error (if there is more than a
483 threshold of nr errors). In addition to alerting all operators implied by the
484 .B \-n
485 key,
486 .B dump
487 interacts with the operator on dump's control terminal at times when
488 .B dump
489 can no longer proceed, or if something is grossly wrong. All questions
490 .B dump
491 poses
492 .I must
493 be answered by typing \*(lqyes\*(rq or \*(lqno\*(rq, appropriately.
494 .PP
495 Since making a dump involves a lot of time and effort for full dumps,
496 .B dump
497 checkpoints itself at the start of each tape volume. If writing that volume
498 fails for some reason,
499 .B dump
500 will, with operator permission, restart itself from the checkpoint after the
501 old tape has been rewound and removed, and a new tape has been mounted.
502 .PP
503 .B Dump
504 tells the operator what is going on at periodic intervals, including usually
505 low estimates of the number of blocks to write, the number of tapes it will
506 take, the time to completion, and the time to the tape change. The output is
507 verbose, so that others know that the terminal controlling
508 .B dump
509 is busy, and will be for some time.
510 .PP
511 In the event of a catastrophic disk event, the time required to restore all the
512 necessary backup tapes or files to disk can be kept to a minimum by staggering
513 the incremental dumps. An efficient method of staggering incremental dumps to
514 minimize the number of tapes follows:
515 .IP \(em
516 Always start with a level 0 backup, for example:
517 .RS 14
518 .B /sbin/dump -0u -f /dev/st0 /usr/src
519 .RE
520 .IP
521 This should be done at set intervals, say once a month or once every two months,
522 and on a set of fresh tapes that is saved forever.
523 .IP \(em
524 After a level 0, dumps of active file systems are taken on a daily basis,
525 with this sequence of dump levels:
526 .RS 14
527 .B 3 2 5 4 7 6 9 8 9 9 ...
528 .RE
529 .IP
530 For the daily dumps, it should be possible to use a fixed number of tapes for
531 each day, used on a weekly basis. Each week, a level 1 dump is taken, and the
532 daily Hanoi sequence repeats beginning with 3. For weekly dumps, another fixed
533 set of tapes per dumped file system is used, also on a cyclical basis.
534 .PP
535 After several months or so, the daily and weekly tapes should get rotated out
536 of the dump cycle and fresh tapes brought in.
537 .PP
538 Another backup strategy is the Tower of Hanoi sequence, which reuses
539 older tapes in a way that for newer dates the available restore points
540 are more frequent, then for older dates (see
541 http://en.wikipedia.org/wiki/Backup_rotation_scheme for additional
542 information).
543 .PP
544 (The 4.3BSD option syntax is implemented for backward compatibility but is not
545 documented here.)
547 .TP
548 .B TAPE
549 If no
550 .B \-f
551 option was specified,
552 .B dump
553 will use the device specified via
554 .B TAPE
555 as the dump device.
556 .B TAPE
557 may be of the form
558 .IR tapename ,
559 .IR host:tapename ,
560 or
561 .IR user@host:tapename .
562 .TP
563 .B RMT
564 The environment variable
565 .B RMT
566 will be used to determine the pathname of the remote
567 .BR rmt (8)
568 program.
569 .TP
570 .B RSH
571 .B Dump
572 uses the contents of this variable to determine the name of the remote shell
573 command to use when doing remote backups (rsh, ssh etc.). If this variable is
574 not set,
575 .BR rcmd (3)
576 will be used, but only root will be able to do remote backups.
578 .TP
579 .I /dev/st0
580 default tape unit to dump to
581 .TP
582 .I __DUMPDATES__
583 dump date records
584 .TP
585 .I /etc/fstab
586 dump table: file systems and frequency
587 .TP
588 .I /etc/mtab
589 dump table: mounted file systems
590 .TP
591 .I /etc/group
592 to find group
593 .I operator
595 .BR fstab (5),
596 .BR restore (8),
597 .BR rmt (8)
599 Many, and verbose.
601 The format of the
602 .I __DUMPDATES__
603 file has changed in release 0.4b34, however, the file will be read
604 correctly with either pre-0.4b34 or 0.4b34 and later versions of
605 .B dump
606 provided that the machine on which
607 .B dump
608 is run did not change timezones (which should be a fairly rare occurence).
610 .B Dump
611 exits with zero status on success. Startup errors are indicated with an exit
612 code of 1; abnormal termination is indicated with an exit code of 3.
613 .SH BUGS
614 It might be considered a bug that this version of dump can only handle ext2/3
615 filesystems. Specifically, it does not work with FAT filesystems.
616 .PP
617 Fewer than 32 read errors (change this with
618 .BR \-I )
619 on the filesystem are ignored. If noticing read errors is important, the output
620 from dump can be parsed to look for lines that contain the text 'read error'.
621 .PP
622 When a read error occurs,
623 .B dump
624 prints out the corresponding physical disk block and sector number and the
625 ext2/3 logical block number. It doesn't print out the corresponing file name or
626 even the inode number. The user has to use
627 .BR debugfs (8),
628 commands
629 .B ncheck
630 and
631 .B icheck
632 to translate the
633 .B ext2blk
634 number printed out by
635 .B dump
636 into an inode number, then into a file name.
637 .PP
638 Each reel requires a new process, so parent processes for reels already written
639 just hang around until the entire tape is written.
640 .PP
641 The estimated number of tapes is not correct if compression is on.
642 .PP
643 It would be nice if
644 .B dump
645 knew about the dump sequence, kept track of the tapes scribbled on, told the
646 operator which tape to mount when, and provided more assistance for the
647 operator running
648 .BR restore .
649 .PP
650 .B Dump
651 cannot do remote backups without being run as root, due to its security history.
652 Presently, it works if you set it setuid (like it used to be), but this might
653 constitute a security risk. Note that you can set
654 .B RSH
655 to use a remote shell program instead.
657 The
658 .B dump/restore
659 backup suite was ported to Linux's Second Extended File System by Remy Card
660 <card@Linux.EU.Org>. He maintained the initial versions of
661 .B dump
662 (up and including 0.4b4, released in january 1997).
663 .PP
664 Starting with 0.4b5, the new maintainer is Stelian Pop <stelian@popies.net>.
666 The
667 .B dump/restore
668 backup suite is available from <http://dump.sourceforge.net>
670 A
671 .B dump
672 command appeared in
673 .B Version 6 AT&T UNIX.