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 December 28, 2020 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 138unless a snapshot is being used. 139The potential for performance improvement indicates that 140use of this option together with snapshots is the recommended 141course of action. 142Beware that 143.Nm 144forks, and the actual memory use may be larger than the specified cache 145size. 146The recommended cache size is between 8 and 32 (megabytes). 147.It Fl c 148Change the defaults for use with a cartridge tape drive, with a density 149of 8000 bpi, and a length of 1700 feet. 150.It Fl D Ar dumpdates 151Specify an alternate path to the 152.Pa dumpdates 153file. 154The default is 155.Pa /etc/dumpdates . 156.It Fl d Ar density 157Set tape density to 158.Ar density . 159The default is 1600BPI. 160.It Fl f Ar file 161Write the backup to 162.Ar file ; 163.Ar file 164may be a special device file 165like 166.Pa /dev/sa0 167(a tape drive), 168.Pa /dev/fd1 169(a floppy disk drive), 170an ordinary file, 171or 172.Sq Fl 173(the standard output). 174Multiple file names may be given as a single argument separated by commas. 175Each file will be used for one dump volume in the order listed; 176if the dump requires more volumes than the number of names given, 177the last file name will used for all remaining volumes after prompting 178for media changes. 179If the name of the file is of the form 180.Dq host:file , 181or 182.Dq user@host:file , 183.Nm 184writes to the named file on the remote host using 185.Xr rmt 8 . 186The default path name of the remote 187.Xr rmt 8 188program is 189.\" rmt path, is the path on the remote host 190.Pa /etc/rmt ; 191this can be overridden by the environment variable 192.Ev RMT . 193.It Fl P Ar pipecommand 194Use 195.Xr popen 3 196to execute the 197.Xr sh 1 198script string defined by 199.Ar pipecommand 200for the output device of each volume. 201This child pipeline's 202.Dv stdin 203.Pq Pa /dev/fd/0 204is redirected from the 205.Nm 206output stream, and the environment variable 207.Ev DUMP_VOLUME 208is set to the current volume number being written. 209After every volume, the writer side of the pipe is closed and 210.Ar pipecommand 211is executed again. 212Subject to the media size specified by 213.Fl B , 214each volume is written in this manner as if the output were a tape drive. 215.It Fl h Ar level 216Honor the user 217.Dq nodump 218flag 219.Pq Dv UF_NODUMP 220only for dumps at or above the given 221.Ar level . 222The default honor level is 1, 223so that incremental backups omit such files 224but full backups retain them. 225.It Fl L 226This option is to notify 227.Nm 228that it is dumping a live file system. 229To obtain a consistent dump image, 230.Nm 231takes a snapshot of the file system in the 232.Pa .snap 233directory in the root of the file system being dumped and 234then does a dump of the snapshot. 235The snapshot is unlinked as soon as the dump starts, and 236is thus removed when the dump is complete. 237This option is ignored for unmounted or read-only file systems. 238If the 239.Pa .snap 240directory does not exist in the root of the file system being dumped, 241a warning will be issued and the 242.Nm 243will revert to the standard behavior. 244This problem can be corrected by creating a 245.Pa .snap 246directory in the root of the file system to be dumped; 247its owner should be 248.Dq Li root , 249its group should be 250.Dq Li operator , 251and its mode should be 252.Dq Li 0770 . 253.It Fl n 254Whenever 255.Nm 256requires operator attention, 257notify all operators in the group 258.Dq operator 259by means similar to a 260.Xr wall 1 . 261.It Fl r 262Be rsync-friendly. 263Normally dump stores the date of the current 264and prior dump in numerous places throughout the dump. 265These scattered changes significantly slow down rsync or 266another incremental file transfer program when they are 267used to update a remote copy of a level 0 dump, 268since the date changes for each dump. 269This option sets both dates to the epoch, permitting 270rsync to be much more efficient when transferring a dump file. 271The 272.Fl r 273option can be used only to create level 0 dumps. 274A dump using the 275.Fl r 276option cannot be used as the basis for a later incremental dump. 277.It Fl R 278Be even more rsync-friendly. 279This option disables the storage of the actual inode access time 280(storing it instead as the inode's modified time). 281This option permits rsync to be even more efficient 282when transferring dumps generated from filesystems with numerous files 283which are not changing other than their access times. 284The 285.Fl R 286option also sets 287.Fl r . 288The 289.Fl R 290option can be used only to create level 0 dumps. 291A dump using the 292.Fl R 293option cannot be used as the basis for a later incremental dump. 294.It Fl S 295Display an estimate of the backup size and the number of 296tapes required, and exit without actually performing the dump. 297.It Fl s Ar feet 298Attempt to calculate the amount of tape needed 299at a particular density. 300If this amount is exceeded, 301.Nm 302prompts for a new tape. 303It is recommended to be a bit conservative on this option. 304The default tape length is 2300 feet. 305.It Fl T Ar date 306Use the specified date as the starting time for the dump 307instead of the time determined from looking in 308the 309.Pa dumpdates 310file. 311The format of date is the same as that of 312.Xr ctime 3 . 313This option is useful for automated dump scripts that wish to 314dump over a specific period of time. 315The 316.Fl T 317option is mutually exclusive from the 318.Fl u 319option. 320.It Fl u 321Update the 322.Pa dumpdates 323file 324after a successful dump. 325The format of 326the 327.Pa dumpdates 328file 329is readable by people, consisting of one 330free format record per line: 331file system name, 332increment level 333and 334.Xr ctime 3 335format dump date. 336There may be only one entry per file system at each level. 337The 338.Pa dumpdates 339file 340may be edited to change any of the fields, 341if necessary. 342The default path for the 343.Pa dumpdates 344file is 345.Pa /etc/dumpdates , 346but the 347.Fl D 348option may be used to change it. 349.It Fl W 350Tell the operator what file systems need to be dumped. 351This information is gleaned from the files 352.Pa dumpdates 353and 354.Pa /etc/fstab . 355The 356.Fl W 357option causes 358.Nm 359to print out, for each file system in 360the 361.Pa dumpdates 362file 363the most recent dump date and level, 364and highlights those file systems that should be dumped. 365If the 366.Fl W 367option is set, all other options are ignored, and 368.Nm 369exits immediately. 370.It Fl w 371Is like 372.Fl W , 373but prints only those file systems which need to be dumped. 374.El 375.Pp 376Directories and regular files which have their 377.Dq nodump 378flag 379.Pq Dv UF_NODUMP 380set will be omitted along with everything under such directories, 381subject to the 382.Fl h 383option. 384.Pp 385The 386.Nm 387utility requires operator intervention on these conditions: 388end of tape, 389end of dump, 390tape write error, 391tape open error or 392disk read error (if there are more than a threshold of 32). 393In addition to alerting all operators implied by the 394.Fl n 395key, 396.Nm 397interacts with the operator on 398.Em dump's 399control terminal at times when 400.Nm 401can no longer proceed, 402or if something is grossly wrong. 403All questions 404.Nm 405poses 406.Em must 407be answered by typing 408.Dq yes 409or 410.Dq no , 411appropriately. 412.Pp 413Since making a dump involves a lot of time and effort for full dumps, 414.Nm 415checkpoints itself at the start of each tape volume. 416If writing that volume fails for some reason, 417.Nm 418will, 419with operator permission, 420restart itself from the checkpoint 421after the old tape has been rewound and removed, 422and a new tape has been mounted. 423.Pp 424The 425.Nm 426utility tells the operator what is going on at periodic intervals 427(every 5 minutes, or promptly after receiving 428.Dv SIGINFO ) , 429including usually low estimates of the number of blocks to write, 430the number of tapes it will take, the time to completion, and 431the time to the tape change. 432The output is verbose, 433so that others know that the terminal 434controlling 435.Nm 436is busy, 437and will be for some time. 438.Pp 439In the event of a catastrophic disk event, the time required 440to restore all the necessary backup tapes or files to disk 441can be kept to a minimum by staggering the incremental dumps. 442An efficient method of staggering incremental dumps 443to minimize the number of tapes follows: 444.Bl -bullet -offset indent 445.It 446Always start with a level 0 backup, for example: 447.Bd -literal -offset indent 448/sbin/dump -0u -f /dev/nsa0 /usr/src 449.Ed 450.Pp 451This should be done at set intervals, say once a month or once every two months, 452and on a set of fresh tapes that is saved forever. 453.It 454After a level 0, dumps of active file systems (file systems with files 455that change, depending on your partition layout some file systems may 456contain only data that does not change) are taken on a daily basis, 457using a modified Tower of Hanoi algorithm, 458with this sequence of dump levels: 459.Bd -literal -offset indent 4603 2 5 4 7 6 9 8 9 9 ... 461.Ed 462.Pp 463For the daily dumps, it should be possible to use a fixed number of tapes 464for each day, used on a weekly basis. 465Each week, a level 1 dump is taken, and 466the daily Hanoi sequence repeats beginning with 3. 467For weekly dumps, another fixed set of tapes per dumped file system is 468used, also on a cyclical basis. 469.El 470.Pp 471After several months or so, the daily and weekly tapes should get 472rotated out of the dump cycle and fresh tapes brought in. 473.Sh ENVIRONMENT 474.Bl -tag -width ".Ev TAPE" 475.It Ev TAPE 476The 477.Ar file 478or device to dump to if the 479.Fl f 480option is not used. 481.It Ev RMT 482Pathname of the remote 483.Xr rmt 8 484program. 485.It Ev RSH 486Pathname of a remote shell program, if not 487.Xr rsh 1 . 488.El 489.Sh FILES 490.Bl -tag -width /etc/dumpdates -compact 491.It Pa /dev/sa0 492default tape unit to dump to 493.It Pa /etc/dumpdates 494dump date records 495(this can be changed; 496see the 497.Fl D 498option) 499.It Pa /etc/fstab 500dump table: file systems and frequency 501.It Pa /etc/group 502to find group 503.Em operator 504.El 505.Sh EXIT STATUS 506Dump exits with zero status on success. 507Startup errors are indicated with an exit code of 1; 508abnormal termination is indicated with an exit code of 3. 509.Sh EXAMPLES 510Dumps the 511.Pa /u 512file system to DVDs using 513.Nm growisofs . 514Uses a 16MB cache, creates a snapshot of the dump, and records the 515.Pa dumpdates 516file. 517.Bd -literal 518/sbin/dump -0u -L -C16 -B4589840 -P 'growisofs -Z /dev/cd0=/dev/fd/0' /u 519.Ed 520.Sh DIAGNOSTICS 521Many, and verbose. 522.Sh SEE ALSO 523.Xr chflags 1 , 524.Xr fstab 5 , 525.Xr restore 8 , 526.Xr rmt 8 527.Sh HISTORY 528A 529.Nm 530utility appeared in 531.At v4 . 532.Sh BUGS 533Fewer than 32 read errors on the file system are ignored, though all 534errors will generate a warning message. 535This is a bit of a compromise. 536In practice, it is possible to generate read errors when doing dumps 537on mounted partitions if the file system is being modified while the 538.Nm 539is running. 540Since dumps are often done in an unattended fashion using 541.Xr cron 8 542jobs asking for Operator intervention would result in the 543.Nm 544dying. 545However, there is nothing wrong with a dump tape written when this sort 546of read error occurs, and there is no reason to terminate the 547.Nm . 548.Pp 549Each reel requires a new process, so parent processes for 550reels already written just hang around until the entire tape 551is written. 552.Pp 553The 554.Nm 555utility with the 556.Fl W 557or 558.Fl w 559options does not report file systems that have never been recorded 560in the 561.Pa dumpdates 562file, 563even if listed in 564.Pa /etc/fstab . 565.Pp 566It would be nice if 567.Nm 568knew about the dump sequence, 569kept track of the tapes scribbled on, 570told the operator which tape to mount when, 571and provided more assistance 572for the operator running 573.Xr restore 8 . 574.Pp 575The 576.Nm 577utility cannot do remote backups without being run as root, due to its 578security history. 579This will be fixed in a later version of 580.Fx . 581Presently, it works if you set it setuid (like it used to be), but this 582might constitute a security risk. 583