1.\" Copyright (c) 1980, 1991, 1993 2.\" Regents of the University of California. 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 3. Neither the name of the University nor the names of its contributors 14.\" may be used to endorse or promote products derived from this software 15.\" without specific prior written permission. 16.\" 17.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27.\" SUCH DAMAGE. 28.\" 29.\" @(#)dump.8 8.3 (Berkeley) 5/1/95 30.\" $FreeBSD$ 31.\" 32.Dd October 3, 2016 33.Dt DUMP 8 34.Os 35.Sh NAME 36.Nm dump , 37.Nm rdump 38.Nd file system backup 39.Sh SYNOPSIS 40.Nm 41.Op Fl 0123456789acLnrRSu 42.Op Fl B Ar records 43.Op Fl b Ar blocksize 44.Op Fl C Ar cachesize 45.Op Fl D Ar dumpdates 46.Op Fl d Ar density 47.Op Fl f Ar file | Fl P Ar pipecommand 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 55The 56.Nm 57utility examines files 58on a file system 59and determines which files 60need to be backed up. 61These files 62are copied to the given disk, tape or other 63storage medium for safe keeping (see the 64.Fl f 65option below for doing remote backups). 66A dump that is larger than the output medium is broken into 67multiple volumes. 68On most media the size is determined by writing until an 69end-of-media indication is returned. 70This can be enforced 71by using the 72.Fl a 73option. 74.Pp 75On media that cannot reliably return an end-of-media indication 76(such as some cartridge tape drives) 77each volume is of a fixed size; 78the actual size is determined by the tape size and density and/or 79.Fl B 80options. 81By default, the same output file name is used for each volume 82after prompting the operator to change media. 83.Pp 84The file system to be dumped is specified by the argument 85.Ar filesystem 86as 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 91may also be invoked as 92.Nm rdump . 93The 94.Bx 4.3 95option syntax is implemented for backward compatibility, but 96is not documented here. 97.Pp 98The following options are supported by 99.Nm : 100.Bl -tag -width Ds 101.It Fl 0-9 102Dump levels. 103A level 0, full backup, 104guarantees the entire file system is copied 105(but see also the 106.Fl h 107option below). 108A level number above 0, 109incremental backup, 110tells dump to 111copy all files new or modified since the 112last dump of any lower level. 113The default level is 0. 114.It Fl a 115.Dq auto-size . 116Bypass all tape length considerations, and enforce writing 117until an end-of-media indication is returned. 118This fits best for most modern tape drives. 119Use of this option is particularly 120recommended when appending to an existing tape, or using a tape 121drive with hardware compression (where you can never be sure about 122the compression ratio). 123.It Fl B Ar records 124The number of kilobytes per output volume, except that if it is 125not an integer multiple of the output block size, 126the command uses the next smaller such multiple. 127This option overrides the calculation of tape size 128based on length and density. 129.It Fl b Ar blocksize 130The number of kilobytes per output block. 131The default block size is 10. 132.It Fl C Ar cachesize 133Specify the cache size in megabytes. 134This will greatly improve performance 135at the cost of 136.Nm 137possibly not noticing changes in the file system between passes. 138It is 139recommended that you always use this option when dumping a snapshot. 140Beware that 141.Nm 142forks, and the actual memory use may be larger than the specified cache 143size. 144The recommended cache size is between 8 and 32 (megabytes). 145.It Fl c 146Change the defaults for use with a cartridge tape drive, with a density 147of 8000 bpi, and a length of 1700 feet. 148.It Fl D Ar dumpdates 149Specify an alternate path to the 150.Pa dumpdates 151file. 152The default is 153.Pa /etc/dumpdates . 154.It Fl d Ar density 155Set tape density to 156.Ar density . 157The default is 1600BPI. 158.It Fl f Ar file 159Write the backup to 160.Ar file ; 161.Ar file 162may be a special device file 163like 164.Pa /dev/sa0 165(a tape drive), 166.Pa /dev/fd1 167(a floppy disk drive), 168an ordinary file, 169or 170.Sq Fl 171(the standard output). 172Multiple file names may be given as a single argument separated by commas. 173Each file will be used for one dump volume in the order listed; 174if the dump requires more volumes than the number of names given, 175the last file name will used for all remaining volumes after prompting 176for media changes. 177If the name of the file is of the form 178.Dq host:file , 179or 180.Dq user@host:file , 181.Nm 182writes to the named file on the remote host using 183.Xr rmt 8 . 184The default path name of the remote 185.Xr rmt 8 186program is 187.\" rmt path, is the path on the remote host 188.Pa /etc/rmt ; 189this can be overridden by the environment variable 190.Ev RMT . 191.It Fl P Ar pipecommand 192Use 193.Xr popen 3 194to execute the 195.Xr sh 1 196script string defined by 197.Ar pipecommand 198for the output device of each volume. 199This child pipeline's 200.Dv stdin 201.Pq Pa /dev/fd/0 202is redirected from the 203.Nm 204output stream, and the environment variable 205.Ev DUMP_VOLUME 206is set to the current volume number being written. 207After every volume, the writer side of the pipe is closed and 208.Ar pipecommand 209is executed again. 210Subject to the media size specified by 211.Fl B , 212each volume is written in this manner as if the output were a tape drive. 213.It Fl h Ar level 214Honor the user 215.Dq nodump 216flag 217.Pq Dv UF_NODUMP 218only for dumps at or above the given 219.Ar level . 220The default honor level is 1, 221so that incremental backups omit such files 222but full backups retain them. 223.It Fl L 224This option is to notify 225.Nm 226that it is dumping a live file system. 227To obtain a consistent dump image, 228.Nm 229takes a snapshot of the file system in the 230.Pa .snap 231directory in the root of the file system being dumped and 232then does a dump of the snapshot. 233The snapshot is unlinked as soon as the dump starts, and 234is thus removed when the dump is complete. 235This option is ignored for unmounted or read-only file systems. 236If the 237.Pa .snap 238directory does not exist in the root of the file system being dumped, 239a warning will be issued and the 240.Nm 241will revert to the standard behavior. 242This problem can be corrected by creating a 243.Pa .snap 244directory in the root of the file system to be dumped; 245its owner should be 246.Dq Li root , 247its group should be 248.Dq Li operator , 249and its mode should be 250.Dq Li 0770 . 251.It Fl n 252Whenever 253.Nm 254requires operator attention, 255notify all operators in the group 256.Dq operator 257by means similar to a 258.Xr wall 1 . 259.It Fl r 260Be rsync-friendly. 261Normally dump stores the date of the current 262and prior dump in numerous places throughout the dump. 263These scattered changes significantly slow down rsync or 264another incremental file transfer program when they are 265used to update a remote copy of a level 0 dump, 266since the date changes for each dump. 267This option sets both dates to the epoch, permitting 268rsync to be much more efficient when transferring a dump file. 269.It Fl R 270Be even more rsync-friendly. 271This option disables the storage of the actual inode access time 272(storing it instead as the inode's modified time). 273This option permits rsync to be even more efficient 274when transferring dumps generated from filesystems with numerous files 275which are not changing other than their access times. 276The 277.Fl R 278option also sets 279.Fl r . 280.It Fl S 281Display an estimate of the backup size and the number of 282tapes required, and exit without actually performing the dump. 283.It Fl s Ar feet 284Attempt to calculate the amount of tape needed 285at a particular density. 286If this amount is exceeded, 287.Nm 288prompts for a new tape. 289It is recommended to be a bit conservative on this option. 290The default tape length is 2300 feet. 291.It Fl T Ar date 292Use the specified date as the starting time for the dump 293instead of the time determined from looking in 294the 295.Pa dumpdates 296file. 297The format of date is the same as that of 298.Xr ctime 3 . 299This option is useful for automated dump scripts that wish to 300dump over a specific period of time. 301The 302.Fl T 303option is mutually exclusive from the 304.Fl u 305option. 306.It Fl u 307Update the 308.Pa dumpdates 309file 310after a successful dump. 311The format of 312the 313.Pa dumpdates 314file 315is readable by people, consisting of one 316free format record per line: 317file system name, 318increment level 319and 320.Xr ctime 3 321format dump date. 322There may be only one entry per file system at each level. 323The 324.Pa dumpdates 325file 326may be edited to change any of the fields, 327if necessary. 328The default path for the 329.Pa dumpdates 330file is 331.Pa /etc/dumpdates , 332but the 333.Fl D 334option may be used to change it. 335.It Fl W 336Tell the operator what file systems need to be dumped. 337This information is gleaned from the files 338.Pa dumpdates 339and 340.Pa /etc/fstab . 341The 342.Fl W 343option causes 344.Nm 345to print out, for each file system in 346the 347.Pa dumpdates 348file 349the most recent dump date and level, 350and highlights those file systems that should be dumped. 351If the 352.Fl W 353option is set, all other options are ignored, and 354.Nm 355exits immediately. 356.It Fl w 357Is like 358.Fl W , 359but prints only those file systems which need to be dumped. 360.El 361.Pp 362Directories and regular files which have their 363.Dq nodump 364flag 365.Pq Dv UF_NODUMP 366set will be omitted along with everything under such directories, 367subject to the 368.Fl h 369option. 370.Pp 371The 372.Nm 373utility requires operator intervention on these conditions: 374end of tape, 375end of dump, 376tape write error, 377tape open error or 378disk read error (if there are more than a threshold of 32). 379In addition to alerting all operators implied by the 380.Fl n 381key, 382.Nm 383interacts with the operator on 384.Em dump's 385control terminal at times when 386.Nm 387can no longer proceed, 388or if something is grossly wrong. 389All questions 390.Nm 391poses 392.Em must 393be answered by typing 394.Dq yes 395or 396.Dq no , 397appropriately. 398.Pp 399Since making a dump involves a lot of time and effort for full dumps, 400.Nm 401checkpoints itself at the start of each tape volume. 402If writing that volume fails for some reason, 403.Nm 404will, 405with operator permission, 406restart itself from the checkpoint 407after the old tape has been rewound and removed, 408and a new tape has been mounted. 409.Pp 410The 411.Nm 412utility tells the operator what is going on at periodic intervals 413(every 5 minutes, or promptly after receiving 414.Dv SIGINFO ) , 415including usually low estimates of the number of blocks to write, 416the number of tapes it will take, the time to completion, and 417the time to the tape change. 418The output is verbose, 419so that others know that the terminal 420controlling 421.Nm 422is busy, 423and will be for some time. 424.Pp 425In the event of a catastrophic disk event, the time required 426to restore all the necessary backup tapes or files to disk 427can be kept to a minimum by staggering the incremental dumps. 428An efficient method of staggering incremental dumps 429to minimize the number of tapes follows: 430.Bl -bullet -offset indent 431.It 432Always start with a level 0 backup, for example: 433.Bd -literal -offset indent 434/sbin/dump -0u -f /dev/nsa0 /usr/src 435.Ed 436.Pp 437This should be done at set intervals, say once a month or once every two months, 438and on a set of fresh tapes that is saved forever. 439.It 440After a level 0, dumps of active file systems (file systems with files 441that change, depending on your partition layout some file systems may 442contain only data that does not change) are taken on a daily basis, 443using a modified Tower of Hanoi algorithm, 444with this sequence of dump levels: 445.Bd -literal -offset indent 4463 2 5 4 7 6 9 8 9 9 ... 447.Ed 448.Pp 449For the daily dumps, it should be possible to use a fixed number of tapes 450for each day, used on a weekly basis. 451Each week, a level 1 dump is taken, and 452the daily Hanoi sequence repeats beginning with 3. 453For weekly dumps, another fixed set of tapes per dumped file system is 454used, also on a cyclical basis. 455.El 456.Pp 457After several months or so, the daily and weekly tapes should get 458rotated out of the dump cycle and fresh tapes brought in. 459.Sh ENVIRONMENT 460.Bl -tag -width ".Ev TAPE" 461.It Ev TAPE 462The 463.Ar file 464or device to dump to if the 465.Fl f 466option is not used. 467.It Ev RMT 468Pathname of the remote 469.Xr rmt 8 470program. 471.It Ev RSH 472Pathname of a remote shell program, if not 473.Xr rsh 1 . 474.El 475.Sh FILES 476.Bl -tag -width /etc/dumpdates -compact 477.It Pa /dev/sa0 478default tape unit to dump to 479.It Pa /etc/dumpdates 480dump date records 481(this can be changed; 482see the 483.Fl D 484option) 485.It Pa /etc/fstab 486dump table: file systems and frequency 487.It Pa /etc/group 488to find group 489.Em operator 490.El 491.Sh EXIT STATUS 492Dump exits with zero status on success. 493Startup errors are indicated with an exit code of 1; 494abnormal termination is indicated with an exit code of 3. 495.Sh EXAMPLES 496Dumps the 497.Pa /u 498file system to DVDs using 499.Nm growisofs . 500Uses a 16MB cache, creates a snapshot of the dump, and records the 501.Pa dumpdates 502file. 503.Bd -literal 504/sbin/dump -0u -L -C16 -B4589840 -P 'growisofs -Z /dev/cd0=/dev/fd/0' /u 505.Ed 506.Sh DIAGNOSTICS 507Many, and verbose. 508.Sh SEE ALSO 509.Xr chflags 1 , 510.Xr fstab 5 , 511.Xr restore 8 , 512.Xr rmt 8 513.Sh HISTORY 514A 515.Nm 516utility appeared in 517.At v4 . 518.Sh BUGS 519Fewer than 32 read errors on the file system are ignored, though all 520errors will generate a warning message. 521This is a bit of a compromise. 522In practice, it is possible to generate read errors when doing dumps 523on mounted partitions if the file system is being modified while the 524.Nm 525is running. 526Since dumps are often done in an unattended fashion using 527.Xr cron 8 528jobs asking for Operator intervention would result in the 529.Nm 530dying. 531However, there is nothing wrong with a dump tape written when this sort 532of read error occurs, and there is no reason to terminate the 533.Nm . 534.Pp 535Each reel requires a new process, so parent processes for 536reels already written just hang around until the entire tape 537is written. 538.Pp 539The 540.Nm 541utility with the 542.Fl W 543or 544.Fl w 545options does not report file systems that have never been recorded 546in the 547.Pa dumpdates 548file, 549even if listed in 550.Pa /etc/fstab . 551.Pp 552It would be nice if 553.Nm 554knew about the dump sequence, 555kept track of the tapes scribbled on, 556told the operator which tape to mount when, 557and provided more assistance 558for the operator running 559.Xr restore 8 . 560.Pp 561The 562.Nm 563utility cannot do remote backups without being run as root, due to its 564security history. 565This will be fixed in a later version of 566.Fx . 567Presently, it works if you set it setuid (like it used to be), but this 568might constitute a security risk. 569