dump/dump.8.in

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  33 .\"     $Id: dump.8.in,v 1.5 1999/11/22 19:08:50 tiniou Exp $
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  35 .Dd __DATE__
  36 .Dt DUMP 8
  37 .Os "dump __VERSION__"
  38 .Sh NAME
  39 .Nm dump
  40 .Nd ext2 filesystem backup
  41 .Sh SYNOPSIS
  42 .Nm dump
  43 .Op Fl 0123456789acknSu
  44 .Op Fl B Ar records
  45 .Op Fl b Ar blocksize
  46 .Op Fl d Ar density
  47 .Op Fl f Ar file
  48 .Op Fl h Ar level
  49 .Op Fl L Ar label
  50 .Op Fl s Ar feet
  51 .Op Fl T Ar date
  52 .Ar filesystem
  53 .Nm dump
  54 .Op Fl 0123456789acknSu
  55 .Op Fl B Ar records
  56 .Op Fl b Ar blocksize
  57 .Op Fl d Ar density
  58 .Op Fl f Ar file
  59 .Op Fl h Ar level
  60 .Op Fl L Ar label
  61 .Op Fl s Ar feet
  62 .Op Fl T Ar date
  63 .Ar directory
  64 .Nm dump
  65 .Op Fl W Li \&| Fl w
  66 .Pp
  67 .in
  68 (The
  69 .Bx 4.3
  70 option syntax is implemented for backward compatibility but
  71 is not documented here.)
  72 .Sh DESCRIPTION
  73 .Nm Dump
  74 examines files
  75 on an ext2 filesystem
  76 and determines which files
  77 need to be backed up. These files
  78 are copied to the given disk, tape or other
  79 storage medium for safe keeping (see the
  80 .Fl f
  81 option below for doing remote backups).
  82 A dump that is larger than the output medium is broken into
  83 multiple volumes.
  84 On most media the size is determined by writing until an
  85 end-of-media indication is returned. 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, density and/or
  94 block count options below.
  95 By default, the same output file name is used for each volume
  96 after prompting the operator to change media.
  97 .Pp
  98 The following options are supported by
  99 .Nm Ns :
 100 .Bl -tag -width Ds
 101 .It Fl 0\-9
 102 Dump levels.
 103 A level 0, full backup,
 104 guarantees the entire file system is copied
 105 (but see also the
 106 .Fl h
 107 option below).
 108 A level number above 0,
 109 incremental backup,
 110 tells
 111 .Nm dump
 112 to
 113 copy all files new or modified since the
 114 last dump of the same or lower level.
 115 The default level is 9.
 116 .It Fl B Ar records
 117 The number of 1 KB blocks per volume.
 118 This option overrides the calculation of tape size
 119 based on length and density.
 120 .It Fl a
 121 .Dq auto-size .
 122 Bypass all tape length considerations, and enforce writing
 123 until an end-of-media indication is returned.  This fits best
 124 for most modern tape drives.  Use of this option is particularly
 125 recommended when appending to an existing tape, or using a tape
 126 drive with hardware compression (where you can never be sure about
 127 the compression ratio).
 128 .It Fl b Ar blocksize
 129 The number of kilobytes per dump record.
 130 Since the IO system slices all requests into chunks of MAXBSIZE
 131 (typically 64KB), it is not possible to use a larger blocksize
 132 without having problems later with
 133 .Xr restore 8 .
 134 Therefore
 135 .Nm dump
 136 will constrain writes to MAXBSIZE.
 137 .It Fl c
 138 Change the defaults for use with a cartridge tape drive, with a density
 139 of 8000 bpi, and a length of 1700 feet.
 140 .It Fl h Ar level
 141 Honor the user
 142 .Dq nodump
 143 flag
 144 .Dp Dv UF_NODUMP
 145 only for dumps at or above the given
 146 .Ar level .
 147 The default honor level is 1,
 148 so that incremental backups omit such files
 149 but full backups retain them.
 150 .It Fl d Ar density
 151 Set tape density to
 152 .Ar density .
 153 The default is 1600BPI.
 154 .It Fl f Ar file
 155 Write the backup to
 156 .Ar file ;
 157 .Ar file
 158 may be a special device file
 159 like
 160 .Pa /dev/st0
 161 (a tape drive),
 162 .Pa /dev/rsd1c
 163 (a floppy disk drive),
 164 an ordinary file,
 165 or
 166 .Ql Fl
 167 (the standard output).
 168 Multiple file names may be given as a single argument separated by commas.
 169 Each file will be used for one dump volume in the order listed;
 170 if the dump requires more volumes than the number of names given,
 171 the last file name will used for all remaining volumes after prompting
 172 for media changes.
 173 If the name of the file is of the form
 174 .Dq host:file
 175 or
 176 .Dq user@host:file
 177 .Nm
 178 writes to the named file on the remote host using
 179 .Xr rmt 8 .
 180 The default path name of the remote
 181 .Xr rmt 8
 182 program is
 183 .\" rmt path, is the path on the remote host
 184 .Pa /etc/rmt ;
 185 this can be overridden by the environment variable
 186 .Ev RMT .
 187 .It Fl k
 188 Use Kerberos authentication to talk to remote tape servers.  (Only
 189 available if this option was enabled when
 190 .Nm
 191 was compiled.)
 192 .It Fl L Ar label
 193 The user-supplied text string
 194 .Ar label
 195 is placed into the dump header, where tools like
 196 .Xr restore 8
 197 and
 198 .Xr file 1
 199 can access it.
 200 Note that this label is limited
 201 to be at most LBLSIZE (currently 16) characters, which must include
 202 the terminating
 203 .Ql \e0 .
 204 .It Fl n
 205 Whenever
 206 .Nm
 207 requires operator attention,
 208 notify all operators in the group
 209 .Dq operator
 210 by means similar to a
 211 .Xr wall 1 .
 212 .It Fl s Ar feet
 213 Attempt to calculate the amount of tape needed
 214 at a particular density.
 215 If this amount is exceeded,
 216 .Nm
 217 prompts for a new tape.
 218 It is recommended to be a bit conservative on this option.
 219 The default tape length is 2300 feet.
 220 .ne 1i
 221 .It Fl S
 222 Size estimate. Determine the amount of space
 223 that is needed to perform the dump without
 224 actually doing it, and display the estimated
 225 number of blocks it will take. This is useful
 226 with incremental dumps to determine how many
 227 volumes of media will be needed.
 228 .It Fl T Ar date
 229 Use the specified date as the starting time for the dump
 230 instead of the time determined from looking in
 231 .Pa __DUMPDATES__ .
 232 The format of
 233 .Ar date
 234 is the same as that of
 235 .Xr ctime 3 .
 236 This option is useful for automated dump scripts that wish to
 237 dump over a specific period of time.
 238 The
 239 .Fl T
 240 option is mutually exclusive from the
 241 .Fl u
 242 option.
 243 .It Fl u
 244 Update the file
 245 .Pa __DUMPDATES__
 246 after a successful dump.
 247 The format of
 248 .Pa __DUMPDATES__
 249 is readable by people, consisting of one
 250 free format record per line:
 251 filesystem name,
 252 increment level
 253 and
 254 .Xr ctime 3
 255 format dump date.
 256 There may be only one entry per filesystem at each level.
 257 The file
 258 .Pa __DUMPDATES__
 259 may be edited to change any of the fields,
 260 if necessary.
 261 .It Fl W
 262 .Nm Dump
 263 tells the operator what file systems need to be dumped.
 264 This information is gleaned from the files
 265 .Pa __DUMPDATES__
 266 and
 267 .Pa /etc/fstab .
 268 The
 269 .Fl W
 270 option causes
 271 .Nm
 272 to print out, for each file system in
 273 .Pa __DUMPDATES__ ,
 274 the most recent dump date and level,
 275 and highlights those file systems that should be dumped.
 276 If the
 277 .Fl W
 278 option is set, all other options are ignored, and
 279 .Nm
 280 exits immediately.
 281 .It Fl w
 282 Is like
 283 .Fl W ,
 284 but prints only those filesystems which need to be dumped.
 285 .El
 286 .Pp
 287 .Nm Dump
 288 requires operator intervention on these conditions:
 289 end of tape,
 290 end of dump,
 291 tape write error,
 292 tape open error or
 293 disk read error (if there is more than a threshold of 32).
 294 In addition to alerting all operators implied by the
 295 .Fl n
 296 key,
 297 .Nm
 298 interacts with the operator on
 299 .Em dump's
 300 control terminal at times when
 301 .Nm
 302 can no longer proceed,
 303 or if something is grossly wrong.
 304 All questions
 305 .Nm
 306 poses
 307 .Em must
 308 be answered by typing
 309 .Dq yes
 310 or
 311 .Dq no ,
 312 appropriately.
 313 .Pp
 314 Since making a dump involves a lot of time and effort for full dumps,
 315 .Nm
 316 checkpoints itself at the start of each tape volume.
 317 If writing that volume fails for some reason,
 318 .Nm
 319 will,
 320 with operator permission,
 321 restart itself from the checkpoint
 322 after the old tape has been rewound and removed,
 323 and a new tape has been mounted.
 324 .Pp
 325 .Nm Dump
 326 tells the operator what is going on at periodic intervals,
 327 including usually low estimates of the number of blocks to write,
 328 the number of tapes it will take, the time to completion, and
 329 the time to the tape change.
 330 The output is verbose,
 331 so that others know that the terminal
 332 controlling
 333 .Nm
 334 is busy,
 335 and will be for some time.
 336 .Pp
 337 In the event of a catastrophic disk event, the time required
 338 to restore all the necessary backup tapes or files to disk
 339 can be kept to a minimum by staggering the incremental dumps.
 340 An efficient method of staggering incremental dumps
 341 to minimize the number of tapes follows:
 342 .Bl -bullet -offset indent
 343 .It
 344 Always start with a level 0 backup, for example:
 345 .Bd -literal -offset indent
 346 /sbin/dump -0u -f /dev/st0 /usr/src
 347 .Ed
 348 .Pp
 349 This should be done at set intervals, say once a month or once every two months,
 350 and on a set of fresh tapes that is saved forever.
 351 .It
 352 After a level 0, dumps of active file
 353 systems are taken on a daily basis,
 354 using a modified Tower of Hanoi algorithm,
 355 with this sequence of dump levels:
 356 .Bd -literal -offset indent
 357 3 2 5 4 7 6 9 8 9 9 ...
 358 .Ed
 359 .Pp
 360 For the daily dumps, it should be possible to use a fixed number of tapes
 361 for each day, used on a weekly basis.
 362 Each week, a level 1 dump is taken, and
 363 the daily Hanoi sequence repeats beginning with 3.
 364 For weekly dumps, another fixed set of tapes per dumped file system is
 365 used, also on a cyclical basis.
 366 .El
 367 .Pp
 368 After several months or so, the daily and weekly tapes should get
 369 rotated out of the dump cycle and fresh tapes brought in.
 370 .Sh ENVIRONMENT
 371 .Bl -tag -width Fl
 372 .It Ev TAPE
 373 If no -f option was specified,
 374 .Nm
 375 will use the device specified via
 376 .Ev TAPE
 377 as the dump device.
 378 .Ev TAPE
 379 may be of the form
 380 .Qq tapename ,
 381 .Qq host:tapename ,
 382 or
 383 .Qq user@host:tapename .
 384 .It Ev RMT
 385 The environment variable
 386 .Ev RMT
 387 will be used to determine the pathname of the remote
 388 .Xr rmt 8
 389 program.
 390 .It Ev RSH
 391 .Nm Dump
 392 uses the contents of this variable to determine the name of the
 393 remote shell command to use when doing remote backups (rsh, ssh etc.).
 394 If this variable is not set,
 395 .Xr rcmd 3
 396 will be used, but only root will be able to do remote backups.
 397 .Sh FILES
 398 .Bl -tag -width __DUMPDATES__ -compact
 399 .It Pa /dev/st0
 400 default tape unit to dump to
 401 .It Pa __DUMPDATES__
 402 dump date records
 403 .It Pa /etc/fstab
 404 dump table: file systems and frequency
 405 .It Pa /etc/group
 406 to find group
 407 .Em operator
 408 .El
 409 .Sh SEE ALSO
 410 .Xr fstab 5 ,
 411 .Xr restore 8 ,
 412 .Xr rmt 8
 413 .Sh DIAGNOSTICS
 414 Many, and verbose.
 415 .Pp
 416 .Nm Dump
 417 exits with zero status on success.
 418 Startup errors are indicated with an exit code of 1;
 419 abnormal termination is indicated with an exit code of 3.
 420 .Sh BUGS
 421 It might be considered a bug that this version of dump can only handle ext2
 422 filesystems.  Specifically, it does not work with FAT filesystems.
 423 .Pp
 424 Fewer than 32 read errors on the filesystem are ignored. If noticing
 425 read errors is important, the output from dump can be parsed to look for lines
 426 that contain the text 'read error'.
 427 .Pp
 428 Each reel requires a new process, so parent processes for
 429 reels already written just hang around until the entire tape
 430 is written.
 431 .Pp
 432 .Nm Dump
 433 with the
 434 .Fl W
 435 or
 436 .Fl w
 437 option does not report filesystems that have never been recorded
 438 in
 439 .Pa __DUMPDATES__ ,
 440 even if listed in
 441 .Pa /etc/fstab .
 442 .Pp
 443 It would be nice if
 444 .Nm
 445 knew about the dump sequence,
 446 kept track of the tapes scribbled on,
 447 told the operator which tape to mount when,
 448 and provided more assistance
 449 for the operator running
 450 .Xr restore .
 451 .Pp
 452 .Nm Dump
 453 cannot do remote backups without being run as root, due to its
 454 security history.
 455 Presently, it works if you set it setuid (like it used to be), but this
 456 might constitute a security risk. Note that you can set RSH to use
 457 a remote shell program instead.
 458 .Sh AUTHOR
 459 The
 460 .Nm dump/restore
 461 backup suit was ported to Linux's Second Extended File System
 462 by Remy Card <card@Linux.EU.Org>. He maintained the initial versions
 463 of dump (up and including 0.4b4, released in january 1997).
 464 .Pp
 465 Starting with 0.4b5, the new maintainer is Stelian Pop
 466 .br
 467 <pop@cybercable.fr>.
 468 .Sh AVAILABILITY
 469 The
 470 .Nm dump/restore
 471 backup suit is available for anonymous ftp from tsx-11.mit.edu
 472 in /pub/linux/ALPHA/ext2fs (development versions) or
 473 /pub/linux/packages/ext2fs (stable versions).
 474 .Pp
 475 An alternate downloading location is http://perso.cybercable.fr/pop/dump.
 476 .Sh HISTORY
 477 A
 478 .Nm
 479 command appeared in
 480 .At v6 .