dump/dump.8.in

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  33 .\"     $Id: dump.8.in,v 1.4 1999/10/30 22:55:51 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 0123456789acknu
  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 0123456789acknu
  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 T Ar date
 222 Use the specified date as the starting time for the dump
 223 instead of the time determined from looking in
 224 .Pa __DUMPDATES__ .
 225 The format of
 226 .Ar date
 227 is the same as that of
 228 .Xr ctime 3 .
 229 This option is useful for automated dump scripts that wish to
 230 dump over a specific period of time.
 231 The
 232 .Fl T
 233 option is mutually exclusive from the
 234 .Fl u
 235 option.
 236 .It Fl u
 237 Update the file
 238 .Pa __DUMPDATES__
 239 after a successful dump.
 240 The format of
 241 .Pa __DUMPDATES__
 242 is readable by people, consisting of one
 243 free format record per line:
 244 filesystem name,
 245 increment level
 246 and
 247 .Xr ctime 3
 248 format dump date.
 249 There may be only one entry per filesystem at each level.
 250 The file
 251 .Pa __DUMPDATES__
 252 may be edited to change any of the fields,
 253 if necessary.
 254 .It Fl W
 255 .Nm Dump
 256 tells the operator what file systems need to be dumped.
 257 This information is gleaned from the files
 258 .Pa __DUMPDATES__
 259 and
 260 .Pa /etc/fstab .
 261 The
 262 .Fl W
 263 option causes
 264 .Nm
 265 to print out, for each file system in
 266 .Pa __DUMPDATES__ ,
 267 the most recent dump date and level,
 268 and highlights those file systems that should be dumped.
 269 If the
 270 .Fl W
 271 option is set, all other options are ignored, and
 272 .Nm
 273 exits immediately.
 274 .It Fl w
 275 Is like
 276 .Fl W ,
 277 but prints only those filesystems which need to be dumped.
 278 .El
 279 .Pp
 280 .Nm Dump
 281 requires operator intervention on these conditions:
 282 end of tape,
 283 end of dump,
 284 tape write error,
 285 tape open error or
 286 disk read error (if there is more than a threshold of 32).
 287 In addition to alerting all operators implied by the
 288 .Fl n
 289 key,
 290 .Nm
 291 interacts with the operator on
 292 .Em dump's
 293 control terminal at times when
 294 .Nm
 295 can no longer proceed,
 296 or if something is grossly wrong.
 297 All questions
 298 .Nm
 299 poses
 300 .Em must
 301 be answered by typing
 302 .Dq yes
 303 or
 304 .Dq no ,
 305 appropriately.
 306 .Pp
 307 Since making a dump involves a lot of time and effort for full dumps,
 308 .Nm
 309 checkpoints itself at the start of each tape volume.
 310 If writing that volume fails for some reason,
 311 .Nm
 312 will,
 313 with operator permission,
 314 restart itself from the checkpoint
 315 after the old tape has been rewound and removed,
 316 and a new tape has been mounted.
 317 .Pp
 318 .Nm Dump
 319 tells the operator what is going on at periodic intervals,
 320 including usually low estimates of the number of blocks to write,
 321 the number of tapes it will take, the time to completion, and
 322 the time to the tape change.
 323 The output is verbose,
 324 so that others know that the terminal
 325 controlling
 326 .Nm
 327 is busy,
 328 and will be for some time.
 329 .Pp
 330 In the event of a catastrophic disk event, the time required
 331 to restore all the necessary backup tapes or files to disk
 332 can be kept to a minimum by staggering the incremental dumps.
 333 An efficient method of staggering incremental dumps
 334 to minimize the number of tapes follows:
 335 .Bl -bullet -offset indent
 336 .It
 337 Always start with a level 0 backup, for example:
 338 .Bd -literal -offset indent
 339 /sbin/dump -0u -f /dev/st0 /usr/src
 340 .Ed
 341 .Pp
 342 This should be done at set intervals, say once a month or once every two months,
 343 and on a set of fresh tapes that is saved forever.
 344 .It
 345 After a level 0, dumps of active file
 346 systems are taken on a daily basis,
 347 using a modified Tower of Hanoi algorithm,
 348 with this sequence of dump levels:
 349 .Bd -literal -offset indent
 350 3 2 5 4 7 6 9 8 9 9 ...
 351 .Ed
 352 .Pp
 353 For the daily dumps, it should be possible to use a fixed number of tapes
 354 for each day, used on a weekly basis.
 355 Each week, a level 1 dump is taken, and
 356 the daily Hanoi sequence repeats beginning with 3.
 357 For weekly dumps, another fixed set of tapes per dumped file system is
 358 used, also on a cyclical basis.
 359 .El
 360 .Pp
 361 After several months or so, the daily and weekly tapes should get
 362 rotated out of the dump cycle and fresh tapes brought in.
 363 .Sh ENVIRONMENT
 364 .Bl -tag -width Fl
 365 .It Ev TAPE
 366 If no -f option was specified,
 367 .Nm
 368 will use the device specified via
 369 .Ev TAPE
 370 as the dump device.
 371 .Ev TAPE
 372 may be of the form
 373 .Qq tapename ,
 374 .Qq host:tapename ,
 375 or
 376 .Qq user@host:tapename .
 377 .It Ev RMT
 378 The environment variable
 379 .Ev RMT
 380 will be used to determine the pathname of the remote
 381 .Xr rmt 8
 382 program.
 383 .It Ev RSH
 384 .Nm Dump
 385 uses the contents of this variable to determine the name of the
 386 remote shell command to use when doing remote backups (rsh, ssh etc.).
 387 If this variable is not set,
 388 .Xr rcmd 3
 389 will be used, but only root will be able to do remote backups.
 390 .Sh FILES
 391 .Bl -tag -width __DUMPDATES__ -compact
 392 .It Pa /dev/st0
 393 default tape unit to dump to
 394 .It Pa __DUMPDATES__
 395 dump date records
 396 .It Pa /etc/fstab
 397 dump table: file systems and frequency
 398 .It Pa /etc/group
 399 to find group
 400 .Em operator
 401 .El
 402 .Sh SEE ALSO
 403 .Xr fstab 5 ,
 404 .Xr restore 8 ,
 405 .Xr rmt 8
 406 .Sh DIAGNOSTICS
 407 Many, and verbose.
 408 .Pp
 409 .Nm Dump
 410 exits with zero status on success.
 411 Startup errors are indicated with an exit code of 1;
 412 abnormal termination is indicated with an exit code of 3.
 413 .Sh BUGS
 414 It might be considered a bug that this version of dump can only handle ext2
 415 filesystems.  Specifically, it does not work with FAT filesystems.
 416 .Pp
 417 Fewer than 32 read errors on the filesystem are ignored. If noticing
 418 read errors is important, the output from dump can be parsed to look for lines
 419 that contain the text 'read error'.
 420 .Pp
 421 Each reel requires a new process, so parent processes for
 422 reels already written just hang around until the entire tape
 423 is written.
 424 .Pp
 425 .Nm Dump
 426 with the
 427 .Fl W
 428 or
 429 .Fl w
 430 option does not report filesystems that have never been recorded
 431 in
 432 .Pa __DUMPDATES__ ,
 433 even if listed in
 434 .Pa /etc/fstab .
 435 .Pp
 436 It would be nice if
 437 .Nm
 438 knew about the dump sequence,
 439 kept track of the tapes scribbled on,
 440 told the operator which tape to mount when,
 441 and provided more assistance
 442 for the operator running
 443 .Xr restore .
 444 .Pp
 445 .Nm Dump
 446 cannot do remote backups without being run as root, due to its
 447 security history.
 448 Presently, it works if you set it setuid (like it used to be), but this
 449 might constitute a security risk. Note that you can set RSH to use
 450 a remote shell program instead.
 451 .Sh AUTHOR
 452 The
 453 .Nm dump/restore
 454 backup suit was ported to Linux's Second Extended File System
 455 by Remy Card <card@Linux.EU.Org>. He maintained the initial versions
 456 of dump (up and including 0.4b4, released in january 1997).
 457 .Pp
 458 Starting with 0.4b5, the new maintainer is Stelian Pop
 459 .br
 460 <pop@cybercable.fr>.
 461 .Sh AVAILABILITY
 462 The
 463 .Nm dump/restore
 464 backup suit is available for anonymous ftp from tsx-11.mit.edu
 465 in /pub/linux/ALPHA/ext2fs (development versions) or
 466 /pub/linux/packages/ext2fs (stable versions).
 467 .Pp
 468 An alternate downloading location is http://perso.cybercable.fr/pop/dump.
 469 .Sh HISTORY
 470 A
 471 .Nm
 472 command appeared in
 473 .At v6 .