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.\" 31.Dd December 28, 2020 32.Dt DUMP 8 33.Os 34.Sh NAME 35.Nm dump , 36.Nm rdump 37.Nd file system backup 38.Sh SYNOPSIS 39.Nm 40.Op Fl 0123456789acLnrRSu 41.Op Fl B Ar records 42.Op Fl b Ar blocksize 43.Op Fl C Ar cachesize 44.Op Fl D Ar dumpdates 45.Op Fl d Ar density 46.Op Fl f Ar file | Fl P Ar pipecommand 47.Op Fl h Ar level 48.Op Fl s Ar feet 49.Op Fl T Ar date 50.Ar filesystem 51.Nm 52.Fl W | Fl w 53.Sh DESCRIPTION 54The 55.Nm 56utility examines files 57on a file system 58and determines which files 59need to be backed up. 60These files 61are copied to the given disk, tape or other 62storage medium for safe keeping (see the 63.Fl f 64option below for doing remote backups). 65A dump that is larger than the output medium is broken into 66multiple volumes. 67On most media the size is determined by writing until an 68end-of-media indication is returned. 69This can be enforced 70by using the 71.Fl a 72option. 73.Pp 74On media that cannot reliably return an end-of-media indication 75(such as some cartridge tape drives) 76each volume is of a fixed size; 77the actual size is determined by the tape size and density and/or 78.Fl B 79options. 80By default, the same output file name is used for each volume 81after prompting the operator to change media. 82.Pp 83The file system to be dumped is specified by the argument 84.Ar filesystem 85as either its device-special file or its mount point 86(if that is in a standard entry in 87.Pa /etc/fstab ) . 88.Pp 89.Nm 90may also be invoked as 91.Nm rdump . 92The 93.Bx 4.3 94option syntax is implemented for backward compatibility, but 95is not documented here. 96.Pp 97The following options are supported by 98.Nm : 99.Bl -tag -width Ds 100.It Fl 0-9 101Dump levels. 102A level 0, full backup, 103guarantees the entire file system is copied 104(but see also the 105.Fl h 106option below). 107A level number above 0, 108incremental backup, 109tells dump to 110copy all files new or modified since the 111last dump of any lower level. 112The default level is 0. 113.It Fl a 114.Dq auto-size . 115Bypass all tape length considerations, and enforce writing 116until an end-of-media indication is returned. 117This fits best for most modern tape drives. 118Use of this option is particularly 119recommended when appending to an existing tape, or using a tape 120drive with hardware compression (where you can never be sure about 121the compression ratio). 122.It Fl B Ar records 123The number of kilobytes per output volume, except that if it is 124not an integer multiple of the output block size, 125the command uses the next smaller such multiple. 126This option overrides the calculation of tape size 127based on length and density. 128.It Fl b Ar blocksize 129The number of kilobytes per output block. 130The default block size is 10. 131.It Fl C Ar cachesize 132Specify the cache size in megabytes. 133This will greatly improve performance 134at the cost of 135.Nm 136possibly not noticing changes in the file system between passes 137unless a snapshot is being used. 138The potential for performance improvement indicates that 139use of this option together with snapshots is the recommended 140course of action. 141Beware that 142.Nm 143forks, and the actual memory use may be larger than the specified cache 144size. 145The recommended cache size is between 8 and 32 (megabytes). 146.It Fl c 147Change the defaults for use with a cartridge tape drive, with a density 148of 8000 bpi, and a length of 1700 feet. 149.It Fl D Ar dumpdates 150Specify an alternate path to the 151.Pa dumpdates 152file. 153The default is 154.Pa /etc/dumpdates . 155.It Fl d Ar density 156Set tape density to 157.Ar density . 158The default is 1600BPI. 159.It Fl f Ar file 160Write the backup to 161.Ar file ; 162.Ar file 163may be a special device file 164like 165.Pa /dev/sa0 166(a tape drive), 167.Pa /dev/fd1 168(a floppy disk drive), 169an ordinary file, 170or 171.Sq Fl 172(the standard output). 173Multiple file names may be given as a single argument separated by commas. 174Each file will be used for one dump volume in the order listed; 175if the dump requires more volumes than the number of names given, 176the last file name will used for all remaining volumes after prompting 177for media changes. 178If the name of the file is of the form 179.Dq host:file , 180or 181.Dq user@host:file , 182.Nm 183writes to the named file on the remote host using 184.Xr rmt 8 . 185The default path name of the remote 186.Xr rmt 8 187program is 188.\" rmt path, is the path on the remote host 189.Pa /etc/rmt ; 190this can be overridden by the environment variable 191.Ev RMT . 192.It Fl P Ar pipecommand 193Use 194.Xr popen 3 195to execute the 196.Xr sh 1 197script string defined by 198.Ar pipecommand 199for the output device of each volume. 200This child pipeline's 201.Dv stdin 202.Pq Pa /dev/fd/0 203is redirected from the 204.Nm 205output stream, and the environment variable 206.Ev DUMP_VOLUME 207is set to the current volume number being written. 208After every volume, the writer side of the pipe is closed and 209.Ar pipecommand 210is executed again. 211Subject to the media size specified by 212.Fl B , 213each volume is written in this manner as if the output were a tape drive. 214.It Fl h Ar level 215Honor the user 216.Dq nodump 217flag 218.Pq Dv UF_NODUMP 219only for dumps at or above the given 220.Ar level . 221The default honor level is 1, 222so that incremental backups omit such files 223but full backups retain them. 224.It Fl L 225This option is to notify 226.Nm 227that it is dumping a live file system. 228To obtain a consistent dump image, 229.Nm 230takes a snapshot of the file system in the 231.Pa .snap 232directory in the root of the file system being dumped and 233then does a dump of the snapshot. 234The snapshot is unlinked as soon as the dump starts, and 235is thus removed when the dump is complete. 236This option is ignored for unmounted or read-only file systems. 237If the 238.Pa .snap 239directory does not exist in the root of the file system being dumped, 240a warning will be issued and the 241.Nm 242will revert to the standard behavior. 243This problem can be corrected by creating a 244.Pa .snap 245directory in the root of the file system to be dumped; 246its owner should be 247.Dq Li root , 248its group should be 249.Dq Li operator , 250and its mode should be 251.Dq Li 0770 . 252.It Fl n 253Whenever 254.Nm 255requires operator attention, 256notify all operators in the group 257.Dq operator 258by means similar to a 259.Xr wall 1 . 260.It Fl r 261Be rsync-friendly. 262Normally dump stores the date of the current 263and prior dump in numerous places throughout the dump. 264These scattered changes significantly slow down rsync or 265another incremental file transfer program when they are 266used to update a remote copy of a level 0 dump, 267since the date changes for each dump. 268This option sets both dates to the epoch, permitting 269rsync to be much more efficient when transferring a dump file. 270The 271.Fl r 272option can be used only to create level 0 dumps. 273A dump using the 274.Fl r 275option cannot be used as the basis for a later incremental dump. 276.It Fl R 277Be even more rsync-friendly. 278This option disables the storage of the actual inode access time 279(storing it instead as the inode's modified time). 280This option permits rsync to be even more efficient 281when transferring dumps generated from filesystems with numerous files 282which are not changing other than their access times. 283The 284.Fl R 285option also sets 286.Fl r . 287The 288.Fl R 289option can be used only to create level 0 dumps. 290A dump using the 291.Fl R 292option cannot be used as the basis for a later incremental dump. 293.It Fl S 294Display an estimate of the backup size and the number of 295tapes required, and exit without actually performing the dump. 296.It Fl s Ar feet 297Attempt to calculate the amount of tape needed 298at a particular density. 299If this amount is exceeded, 300.Nm 301prompts for a new tape. 302It is recommended to be a bit conservative on this option. 303The default tape length is 2300 feet. 304.It Fl T Ar date 305Use the specified date as the starting time for the dump 306instead of the time determined from looking in 307the 308.Pa dumpdates 309file. 310The format of date is the same as that of 311.Xr ctime 3 . 312This option is useful for automated dump scripts that wish to 313dump over a specific period of time. 314The 315.Fl T 316option is mutually exclusive from the 317.Fl u 318option. 319.It Fl u 320Update the 321.Pa dumpdates 322file 323after a successful dump. 324The format of 325the 326.Pa dumpdates 327file 328is readable by people, consisting of one 329free format record per line: 330file system name, 331increment level 332and 333.Xr ctime 3 334format dump date. 335There may be only one entry per file system at each level. 336The 337.Pa dumpdates 338file 339may be edited to change any of the fields, 340if necessary. 341The default path for the 342.Pa dumpdates 343file is 344.Pa /etc/dumpdates , 345but the 346.Fl D 347option may be used to change it. 348.It Fl W 349Tell the operator what file systems need to be dumped. 350This information is gleaned from the files 351.Pa dumpdates 352and 353.Pa /etc/fstab . 354The 355.Fl W 356option causes 357.Nm 358to print out, for each file system in 359the 360.Pa dumpdates 361file 362the most recent dump date and level, 363and highlights those file systems that should be dumped. 364If the 365.Fl W 366option is set, all other options are ignored, and 367.Nm 368exits immediately. 369.It Fl w 370Is like 371.Fl W , 372but prints only those file systems which need to be dumped. 373.El 374.Pp 375Directories and regular files which have their 376.Dq nodump 377flag 378.Pq Dv UF_NODUMP 379set will be omitted along with everything under such directories, 380subject to the 381.Fl h 382option. 383.Pp 384The 385.Nm 386utility requires operator intervention on these conditions: 387end of tape, 388end of dump, 389tape write error, 390tape open error or 391disk read error (if there are more than a threshold of 32). 392In addition to alerting all operators implied by the 393.Fl n 394key, 395.Nm 396interacts with the operator on 397.Em dump's 398control terminal at times when 399.Nm 400can no longer proceed, 401or if something is grossly wrong. 402All questions 403.Nm 404poses 405.Em must 406be answered by typing 407.Dq yes 408or 409.Dq no , 410appropriately. 411.Pp 412Since making a dump involves a lot of time and effort for full dumps, 413.Nm 414checkpoints itself at the start of each tape volume. 415If writing that volume fails for some reason, 416.Nm 417will, 418with operator permission, 419restart itself from the checkpoint 420after the old tape has been rewound and removed, 421and a new tape has been mounted. 422.Pp 423The 424.Nm 425utility tells the operator what is going on at periodic intervals 426(every 5 minutes, or promptly after receiving 427.Dv SIGINFO ) , 428including usually low estimates of the number of blocks to write, 429the number of tapes it will take, the time to completion, and 430the time to the tape change. 431The output is verbose, 432so that others know that the terminal 433controlling 434.Nm 435is busy, 436and will be for some time. 437.Pp 438In the event of a catastrophic disk event, the time required 439to restore all the necessary backup tapes or files to disk 440can be kept to a minimum by staggering the incremental dumps. 441An efficient method of staggering incremental dumps 442to minimize the number of tapes follows: 443.Bl -bullet -offset indent 444.It 445Always start with a level 0 backup, for example: 446.Bd -literal -offset indent 447/sbin/dump -0u -f /dev/nsa0 /usr/src 448.Ed 449.Pp 450This should be done at set intervals, say once a month or once every two months, 451and on a set of fresh tapes that is saved forever. 452.It 453After a level 0, dumps of active file systems (file systems with files 454that change, depending on your partition layout some file systems may 455contain only data that does not change) are taken on a daily basis, 456using a modified Tower of Hanoi algorithm, 457with this sequence of dump levels: 458.Bd -literal -offset indent 4593 2 5 4 7 6 9 8 9 9 ... 460.Ed 461.Pp 462For the daily dumps, it should be possible to use a fixed number of tapes 463for each day, used on a weekly basis. 464Each week, a level 1 dump is taken, and 465the daily Hanoi sequence repeats beginning with 3. 466For weekly dumps, another fixed set of tapes per dumped file system is 467used, also on a cyclical basis. 468.El 469.Pp 470After several months or so, the daily and weekly tapes should get 471rotated out of the dump cycle and fresh tapes brought in. 472.Sh ENVIRONMENT 473.Bl -tag -width ".Ev TAPE" 474.It Ev TAPE 475The 476.Ar file 477or device to dump to if the 478.Fl f 479option is not used. 480.It Ev RMT 481Pathname of the remote 482.Xr rmt 8 483program. 484.It Ev RSH 485Pathname of a remote shell program, if not 486.Xr rsh 1 . 487.El 488.Sh FILES 489.Bl -tag -width /etc/dumpdates -compact 490.It Pa /dev/sa0 491default tape unit to dump to 492.It Pa /etc/dumpdates 493dump date records 494(this can be changed; 495see the 496.Fl D 497option) 498.It Pa /etc/fstab 499dump table: file systems and frequency 500.It Pa /etc/group 501to find group 502.Em operator 503.El 504.Sh EXIT STATUS 505Dump exits with zero status on success. 506Startup errors are indicated with an exit code of 1; 507abnormal termination is indicated with an exit code of 3. 508.Sh EXAMPLES 509Dumps the 510.Pa /u 511file system to DVDs using 512.Nm growisofs . 513Uses a 16MB cache, creates a snapshot of the dump, and records the 514.Pa dumpdates 515file. 516.Bd -literal 517/sbin/dump -0u -L -C16 -B4589840 -P 'growisofs -Z /dev/cd0=/dev/fd/0' /u 518.Ed 519.Sh DIAGNOSTICS 520Many, and verbose. 521.Sh SEE ALSO 522.Xr chflags 1 , 523.Xr fstab 5 , 524.Xr restore 8 , 525.Xr rmt 8 526.Sh HISTORY 527A 528.Nm 529utility appeared in 530.At v4 . 531.Sh BUGS 532Fewer than 32 read errors on the file system are ignored, though all 533errors will generate a warning message. 534This is a bit of a compromise. 535In practice, it is possible to generate read errors when doing dumps 536on mounted partitions if the file system is being modified while the 537.Nm 538is running. 539Since dumps are often done in an unattended fashion using 540.Xr cron 8 541jobs asking for Operator intervention would result in the 542.Nm 543dying. 544However, there is nothing wrong with a dump tape written when this sort 545of read error occurs, and there is no reason to terminate the 546.Nm . 547.Pp 548Each reel requires a new process, so parent processes for 549reels already written just hang around until the entire tape 550is written. 551.Pp 552The 553.Nm 554utility with the 555.Fl W 556or 557.Fl w 558options does not report file systems that have never been recorded 559in the 560.Pa dumpdates 561file, 562even if listed in 563.Pa /etc/fstab . 564.Pp 565It would be nice if 566.Nm 567knew about the dump sequence, 568kept track of the tapes scribbled on, 569told the operator which tape to mount when, 570and provided more assistance 571for the operator running 572.Xr restore 8 . 573.Pp 574The 575.Nm 576utility cannot do remote backups without being run as root, due to its 577security history. 578This will be fixed in a later version of 579.Fx . 580Presently, it works if you set it setuid (like it used to be), but this 581might constitute a security risk. 582