dump/dump.8.in

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  33 .\"     @(#)dump.8      8.3 (Berkeley) 5/1/95
  34 .\"     $Id: dump.8.in,v 1.1 1999/10/11 13:08:07 stelian Exp $
  35 .\"
  36 .Dd __DATE__
  37 .Dt DUMP 8
  38 .Os "__VERSION__"
  39 .Sh NAME
  40 .Nm dump
  41 .Nd ext2 filesystem backup
  42 .Sh SYNOPSIS
  43 .Nm dump
  44 .Op Fl 0123456789acknu
  45 .Op Fl B Ar records
  46 .Op Fl b Ar blocksize
  47 .Op Fl d Ar density
  48 .Op Fl f Ar file
  49 .Op Fl h Ar level
  50 .Op Fl L Ar label
  51 .Op Fl s Ar feet
  52 .Op Fl T Ar date
  53 .Ar filesystem
  54 .Nm dump
  55 .Op Fl 0123456789acknu
  56 .Op Fl B Ar records
  57 .Op Fl b Ar blocksize
  58 .Op Fl d Ar density
  59 .Op Fl f Ar file
  60 .Op Fl h Ar level
  61 .Op Fl L Ar label
  62 .Op Fl s Ar feet
  63 .Op Fl T Ar date
  64 .Ar directory
  65 .Nm dump
  66 .Op Fl W Li \&| Fl w
  67 .Pp
  68 .in
  69 (The
  70 .Bx 4.3
  71 option syntax is implemented for backward compatibility but
  72 is not documented here.)
  73 .Sh DESCRIPTION
  74 .Nm Dump
  75 examines files
  76 on an ext2 filesystem
  77 and determines which files
  78 need to be backed up. These files
  79 are copied to the given disk, tape or other
  80 storage medium for safe keeping (see the
  81 .Fl f
  82 option below for doing remote backups).
  83 A dump that is larger than the output medium is broken into
  84 multiple volumes.
  85 On most media the size is determined by writing until an
  86 end-of-media indication is returned. This can be enforced
  87 by using the
  88 .Fl a
  89 option.
  90 .Pp
  91 On media that cannot reliably return an end-of-media indication
  92 (such as some cartridge tape drives),
  93 each volume is of a fixed size;
  94 the actual size is determined by the tape size, density and/or
  95 block count options below.
  96 By default, the same output file name is used for each volume
  97 after prompting the operator to change media.
  98 .Pp
  99 The following options are supported by
 100 .Nm Ns :
 101 .Bl -tag -width Ds
 102 .It Fl 0\-9
 103 Dump levels.
 104 A level 0, full backup,
 105 guarantees the entire file system is copied
 106 (but see also the
 107 .Fl h
 108 option below).
 109 A level number above 0,
 110 incremental backup,
 111 tells
 112 .Nm dump
 113 to
 114 copy all files new or modified since the
 115 last dump of the same or lower level.
 116 The default level is 9.
 117 .It Fl B Ar records
 118 The number of 1 KB blocks per volume.
 119 This option overrides the calculation of tape size
 120 based on length and density.
 121 .It Fl a
 122 .Dq auto-size .
 123 Bypass all tape length considerations, and enforce writing
 124 until an end-of-media indication is returned.  This fits best
 125 for most modern tape drives.  Use of this option is particularly
 126 recommended when appending to an existing tape, or using a tape
 127 drive with hardware compression (where you can never be sure about
 128 the compression ratio).
 129 .It Fl b Ar blocksize
 130 The number of kilobytes per dump record.
 131 Since the IO system slices all requests into chunks of MAXBSIZE
 132 (typically 64KB), it is not possible to use a larger blocksize
 133 without having problems later with
 134 .Xr restore 8 .
 135 Therefore
 136 .Nm dump
 137 will constrain writes to MAXBSIZE.
 138 .It Fl c
 139 Change the defaults for use with a cartridge tape drive, with a density
 140 of 8000 bpi, and a length of 1700 feet.
 141 .It Fl h Ar level
 142 Honor the user
 143 .Dq nodump
 144 flag
 145 .Dp Dv UF_NODUMP
 146 only for dumps at or above the given
 147 .Ar level .
 148 The default honor level is 1,
 149 so that incremental backups omit such files
 150 but full backups retain them.
 151 .It Fl d Ar density
 152 Set tape density to
 153 .Ar density .
 154 The default is 1600BPI.
 155 .It Fl f Ar file
 156 Write the backup to
 157 .Ar file ;
 158 .Ar file
 159 may be a special device file
 160 like
 161 .Pa /dev/st0
 162 (a tape drive),
 163 .Pa /dev/rsd1c
 164 (a floppy disk drive),
 165 an ordinary file,
 166 or
 167 .Ql Fl
 168 (the standard output).
 169 Multiple file names may be given as a single argument separated by commas.
 170 Each file will be used for one dump volume in the order listed;
 171 if the dump requires more volumes than the number of names given,
 172 the last file name will used for all remaining volumes after prompting
 173 for media changes.
 174 If the name of the file is of the form
 175 .Dq host:file
 176 or
 177 .Dq user@host:file
 178 .Nm
 179 writes to the named file on the remote host using
 180 .Xr rmt 8 .
 181 The default path name of the remote
 182 .Xr rmt 8
 183 program is
 184 .\" rmt path, is the path on the remote host
 185 .Pa /etc/rmt ;
 186 this can be overridden by the environment variable
 187 .Ev RMT .
 188 .It Fl k
 189 Use Kerberos authentication to talk to remote tape servers.  (Only
 190 available if this option was enabled when
 191 .Nm
 192 was compiled.)
 193 .It Fl L Ar label
 194 The user-supplied text string
 195 .Ar label
 196 is placed into the dump header, where tools like
 197 .Xr restore 8
 198 and
 199 .Xr file 1
 200 can access it.
 201 Note that this label is limited
 202 to be at most LBLSIZE (currently 16) characters, which must include
 203 the terminating
 204 .Ql \e0 .
 205 .It Fl n
 206 Whenever
 207 .Nm
 208 requires operator attention,
 209 notify all operators in the group
 210 .Dq operator
 211 by means similar to a
 212 .Xr wall 1 .
 213 .It Fl s Ar feet
 214 Attempt to calculate the amount of tape needed
 215 at a particular density.
 216 If this amount is exceeded,
 217 .Nm
 218 prompts for a new tape.
 219 It is recommended to be a bit conservative on this option.
 220 The default tape length is 2300 feet.
 221 .ne 1i
 222 .It Fl T Ar date
 223 Use the specified date as the starting time for the dump
 224 instead of the time determined from looking in
 225 .Pa __DUMPDATES__ .
 226 The format of
 227 .Ar date
 228 is the same as that of
 229 .Xr ctime 3 .
 230 This option is useful for automated dump scripts that wish to
 231 dump over a specific period of time.
 232 The
 233 .Fl T
 234 option is mutually exclusive from the
 235 .Fl u
 236 option.
 237 .It Fl u
 238 Update the file
 239 .Pa __DUMPDATES__
 240 after a successful dump.
 241 The format of
 242 .Pa __DUMPDATES__
 243 is readable by people, consisting of one
 244 free format record per line:
 245 filesystem name,
 246 increment level
 247 and
 248 .Xr ctime 3
 249 format dump date.
 250 There may be only one entry per filesystem at each level.
 251 The file
 252 .Pa __DUMPDATES__
 253 may be edited to change any of the fields,
 254 if necessary.
 255 .It Fl W
 256 .Nm Dump
 257 tells the operator what file systems need to be dumped.
 258 This information is gleaned from the files
 259 .Pa __DUMPDATES__
 260 and
 261 .Pa /etc/fstab .
 262 The
 263 .Fl W
 264 option causes
 265 .Nm
 266 to print out, for each file system in
 267 .Pa __DUMPDATES__ ,
 268 the most recent dump date and level,
 269 and highlights those file systems that should be dumped.
 270 If the
 271 .Fl W
 272 option is set, all other options are ignored, and
 273 .Nm
 274 exits immediately.
 275 .It Fl w
 276 Is like
 277 .Fl W ,
 278 but prints only those filesystems which need to be dumped.
 279 .El
 280 .Pp
 281 .Nm Dump
 282 requires operator intervention on these conditions:
 283 end of tape,
 284 end of dump,
 285 tape write error,
 286 tape open error or
 287 disk read error (if there is more than a threshold of 32).
 288 In addition to alerting all operators implied by the
 289 .Fl n
 290 key,
 291 .Nm
 292 interacts with the operator on
 293 .Em dump's
 294 control terminal at times when
 295 .Nm
 296 can no longer proceed,
 297 or if something is grossly wrong.
 298 All questions
 299 .Nm
 300 poses
 301 .Em must
 302 be answered by typing
 303 .Dq yes
 304 or
 305 .Dq no ,
 306 appropriately.
 307 .Pp
 308 Since making a dump involves a lot of time and effort for full dumps,
 309 .Nm
 310 checkpoints itself at the start of each tape volume.
 311 If writing that volume fails for some reason,
 312 .Nm
 313 will,
 314 with operator permission,
 315 restart itself from the checkpoint
 316 after the old tape has been rewound and removed,
 317 and a new tape has been mounted.
 318 .Pp
 319 .Nm Dump
 320 tells the operator what is going on at periodic intervals,
 321 including usually low estimates of the number of blocks to write,
 322 the number of tapes it will take, the time to completion, and
 323 the time to the tape change.
 324 The output is verbose,
 325 so that others know that the terminal
 326 controlling
 327 .Nm
 328 is busy,
 329 and will be for some time.
 330 .Pp
 331 In the event of a catastrophic disk event, the time required
 332 to restore all the necessary backup tapes or files to disk
 333 can be kept to a minimum by staggering the incremental dumps.
 334 An efficient method of staggering incremental dumps
 335 to minimize the number of tapes follows:
 336 .Bl -bullet -offset indent
 337 .It
 338 Always start with a level 0 backup, for example:
 339 .Bd -literal -offset indent
 340 /sbin/dump -0u -f /dev/st0 /usr/src
 341 .Ed
 342 .Pp
 343 This should be done at set intervals, say once a month or once every two months,
 344 and on a set of fresh tapes that is saved forever.
 345 .It
 346 After a level 0, dumps of active file
 347 systems are taken on a daily basis,
 348 using a modified Tower of Hanoi algorithm,
 349 with this sequence of dump levels:
 350 .Bd -literal -offset indent
 351 3 2 5 4 7 6 9 8 9 9 ...
 352 .Ed
 353 .Pp
 354 For the daily dumps, it should be possible to use a fixed number of tapes
 355 for each day, used on a weekly basis.
 356 Each week, a level 1 dump is taken, and
 357 the daily Hanoi sequence repeats beginning with 3.
 358 For weekly dumps, another fixed set of tapes per dumped file system is
 359 used, also on a cyclical basis.
 360 .El
 361 .Pp
 362 After several months or so, the daily and weekly tapes should get
 363 rotated out of the dump cycle and fresh tapes brought in.
 364 .Sh ENVIRONMENT
 365 .Bl -tag -width Fl
 366 .It Ev TAPE
 367 If no -f option was specified,
 368 .Nm
 369 will use the device specified via
 370 .Ev TAPE
 371 as the dump device.
 372 .Ev TAPE
 373 may be of the form
 374 .Qq tapename ,
 375 .Qq host:tapename ,
 376 or
 377 .Qq user@host:tapename .
 378 .It Ev RMT
 379 The environment variable
 380 .Ev RMT
 381 will be used to determine the pathname of the remote
 382 .Xr rmt 8
 383 program.
 384 .Sh FILES
 385 .Bl -tag -width __DUMPDATES__ -compact
 386 .It Pa /dev/st0
 387 default tape unit to dump to
 388 .It Pa __DUMPDATES__
 389 dump date records
 390 .It Pa /etc/fstab
 391 dump table: file systems and frequency
 392 .It Pa /etc/group
 393 to find group
 394 .Em operator
 395 .El
 396 .Sh SEE ALSO
 397 .Xr fstab 5 ,
 398 .Xr restore 8 ,
 399 .Xr rmt 8
 400 .Sh DIAGNOSTICS
 401 Many, and verbose.
 402 .Pp
 403 .Nm Dump
 404 exits with zero status on success.
 405 Startup errors are indicated with an exit code of 1;
 406 abnormal termination is indicated with an exit code of 3.
 407 .Sh BUGS
 408 It might be considered a bug that this version of dump can only handle ext2
 409 filesystems.  Specifically, it does not work with FAT filesystems.
 410 .Pp
 411 Fewer than 32 read errors on the filesystem are ignored. If noticing
 412 read errors is important, the output from dump can be parsed to look for lines
 413 that contain the text 'read error'.
 414 .Pp
 415 Each reel requires a new process, so parent processes for
 416 reels already written just hang around until the entire tape
 417 is written.
 418 .Pp
 419 .Nm Dump
 420 with the
 421 .Fl W
 422 or
 423 .Fl w
 424 option does not report filesystems that have never been recorded
 425 in
 426 .Pa __DUMPDATES__ ,
 427 even if listed in
 428 .Pa /etc/fstab .
 429 .Pp
 430 It would be nice if
 431 .Nm
 432 knew about the dump sequence,
 433 kept track of the tapes scribbled on,
 434 told the operator which tape to mount when,
 435 and provided more assistance
 436 for the operator running
 437 .Xr restore .
 438 .Pp
 439 .Nm Dump
 440 cannot do remote backups without being run as root, due to its
 441 security history.  This will be fixed in a later version of
 442 .Bx Free .
 443 Presently, it works if you set it setuid (like it used to be), but this
 444 might constitute a security risk.
 445 .Sh AUTHOR
 446 The
 447 .Nm dump/restore
 448 backup suit was ported to Linux's Second Extended File System
 449 by Remy Card <card@Linux.EU.Org>. He maintained the initial versions
 450 of dump (up and including 0.4b4, released in january 1997).
 451 .Pp
 452 Starting with 0.4b5, the new maintainer is Stelian Pop
 453 .br
 454 <pop@cybercable.fr>.
 455 .Sh AVAILABILITY
 456 The
 457 .Nm dump/restore
 458 backup suit is available for anonymous ftp from tsx-11.mit.edu
 459 in /pub/linux/ALPHA/ext2fs (development versions) or
 460 /pub/linux/packages/ext2fs (stable versions).
 461 .Pp
 462 An alternate downloading location is http://perso.cybercable.fr/pop/dump.
 463 .Sh HISTORY
 464 A
 465 .Nm
 466 command appeared in
 467 .At v6 .