4 \section*{Automatic Volume Recycling}
5 \label{_ChapterStart22}
6 \index[general]{Recycling!Automatic Volume }
7 \index[general]{Automatic Volume Recycling }
8 \addcontentsline{toc}{section}{Automatic Volume Recycling}
10 By default, once Bacula starts writing a Volume, it can append to the
11 volume, but it will not overwrite the existing data thus destroying it.
12 However when Bacula {\bf recycles} a Volume, the Volume becomes available
13 for being reused, and Bacula can at some later time overwrite the previous
14 contents of that Volume. Thus all previous data will be lost. If the
15 Volume is a tape, the tape will be rewritten from the beginning. If the
16 Volume is a disk file, the file will be truncated before being rewritten.
18 You may not want Bacula to automatically recycle (reuse) tapes. This would
19 require a large number of tapes though, and in such a case, it is possible
20 to manually recycle tapes. For more on manual recycling, see the section
21 entitled \ilink{ Manually Recycling Volumes}{manualrecycling} below in this
24 Most people prefer to have a Pool of tapes that are used for daily backups and
25 recycled once a week, another Pool of tapes that are used for Full backups
26 once a week and recycled monthly, and finally a Pool of tapes that are used
27 once a month and recycled after a year or two. With a scheme like this, the
28 number of tapes in your pool or pools remains constant.
30 By properly defining your Volume Pools with appropriate Retention periods,
31 Bacula can manage the recycling (such as defined above) automatically.
33 Automatic recycling of Volumes is controlled by three records in the {\bf
34 Pool} resource definition in the Director's configuration file. These three
39 \item VolumeRetention = \lt{}time\gt{}
43 The above three directives are all you need assuming that you fill
44 each of your Volumes then wait the Volume Retention period before
45 reusing them. If you want Bacula to stop using a Volume and recycle
46 it before it is full, you will need to use one or more additional
49 \item Use Volume Once = yes
50 \item Volume Use Duration = ttt
51 \item Maximum Volume Jobs = nnn
52 \item Maximum Volume Bytes = mmm
55 the \ilink{Basic Volume Management}{_ChapterStart39} chapter
56 of this manual for more complete examples.
58 Automatic recycling of Volumes is performed by Bacula only when it wants a
59 new Volume and no appendable Volumes are available in the Pool. It will then
60 search the Pool for any Volumes with the {\bf Recycle} flag set and whose
61 Volume Status is {\bf Full}. At that point, the recycling occurs in two steps.
62 The first is that the Catalog for a Volume must be purged of all Jobs and
63 Files contained on that Volume, and the second step is the actual recycling of
64 the Volume. The Volume will be purged if the VolumeRetention period has
65 expired. When a Volume is marked as Purged, it means that no Catalog records
66 reference that Volume, and the Volume can be recycled. Until recycling
67 actually occurs, the Volume data remains intact. If no Volumes can be found
68 for recycling for any of the reasons stated above, Bacula will request
69 operator intervention (i.e. it will ask you to label a new volume).
71 A key point mentioned above, that can be a source of frustration, is that Bacula
72 will only recycle purged Volumes if there is no other appendable Volume
73 available, otherwise, it will always write to an appendable Volume before
74 recycling even if there are Volume marked as Purged. This preserves your data
75 as long as possible. So, if you wish to "force" Bacula to use a purged
76 Volume, you must first ensure that no other Volume in the Pool is marked {\bf
77 Append}. If necessary, you can manually set a volume to {\bf Full}. The reason
78 for this is that Bacula wants to preserve the data on your old tapes (even
79 though purged from the catalog) as long as absolutely possible before
80 overwriting it. There are also a number of directives such as
81 {\bf Volume Use Duration} that will automatically mark a volume as {\bf
82 Used} and thus no longer appendable.
85 \subsection*{Automatic Pruning}
86 \index[general]{Automatic Pruning}
87 \index[general]{Pruning!Automatic}
88 \addcontentsline{toc}{subsection}{Automatic Pruning}
90 As Bacula writes files to tape, it keeps a list of files, jobs, and volumes
91 in a database called the catalog. Among other things, the database helps
92 Bacula to decide which files to back up in an incremental or differential
93 backup, and helps you locate files on past backups when you want to restore
94 something. However, the catalog will grow larger and larger as time goes
95 on, and eventually it can become unacceptably large.
97 Bacula's process for removing entries from the catalog is called Pruning.
98 The default is Automatic Pruning, which means that once an entry reaches a
99 certain age (e.g. 30 days old) it is removed from the catalog. Once a job
100 has been pruned, you can still restore it from the backup tape, but one
101 additional step is required: scanning the volume with bscan. The
102 alternative to Automatic Pruning is Manual Pruning, in which you explicitly
103 tell Bacula to erase the catalog entries for a volume. You'd usually do
104 this when you want to reuse a Bacula volume, because there's no point in
105 keeping a list of files that USED TO BE on a tape. Or, if the catalog is
106 starting to get too big, you could prune the oldest jobs to save space.
107 Manual pruning is done with the \ilink{ prune command}{ManualPruning} in
108 the console. (thanks to Bryce Denney for the above explanation).
110 \subsection*{Pruning Directives}
111 \index[general]{Pruning Directives }
112 \index[general]{Directives!Pruning }
113 \addcontentsline{toc}{subsection}{Pruning Directives}
115 There are three pruning durations. All apply to catalog database records and
116 not to the actual data in a Volume. The pruning (or retention) durations are
117 for: Volumes (Media records), Jobs (Job records), and Files (File records).
118 The durations inter-depend a bit because if Bacula prunes a Volume, it
119 automatically removes all the Job records, and all the File records. Also when
120 a Job record is pruned, all the File records for that Job are also pruned
121 (deleted) from the catalog.
123 Having the File records in the database means that you can examine all the
124 files backed up for a particular Job. They take the most space in the catalog
125 (probably 90-95\% of the total). When the File records are pruned, the Job
126 records can remain, and you can still examine what Jobs ran, but not the
127 details of the Files backed up. In addition, without the File records, you
128 cannot use the Console restore command to restore the files.
130 When a Job record is pruned, the Volume (Media record) for that Job can still
131 remain in the database, and if you do a "list volumes", you will see the
132 volume information, but the Job records (and its File records) will no longer
135 In each case, pruning removes information about where older files are, but it
136 also prevents the catalog from growing to be too large. You choose the
137 retention periods in function of how many files you are backing up and the
138 time periods you want to keep those records online, and the size of the
139 database. You can always re-insert the records (with 98\% of the original data)
140 by using "bscan" to scan in a whole Volume or any part of the volume that
143 By setting {\bf AutoPrune} to {\bf yes} you will permit {\bf Bacula} to
144 automatically prune all Volumes in the Pool when a Job needs another Volume.
145 Volume pruning means removing records from the catalog. It does not shrink the
146 size of the Volume or affect the Volume data until the Volume gets
147 overwritten. When a Job requests another volume and there are no Volumes with
148 Volume Status {\bf Append} available, Bacula will begin volume pruning. This
149 means that all Jobs that are older than the {\bf VolumeRetention} period will
150 be pruned from every Volume that has Volume Status {\bf Full} or {\bf Used}
151 and has Recycle set to {\bf yes}. Pruning consists of deleting the
152 corresponding Job, File, and JobMedia records from the catalog database. No
153 change to the physical data on the Volume occurs during the pruning process.
154 When all files are pruned from a Volume (i.e. no records in the catalog), the
155 Volume will be marked as {\bf Purged} implying that no Jobs remain on the
156 volume. The Pool records that control the pruning are described below.
160 \item [AutoPrune = \lt{}yes|no\gt{}]
161 \index[console]{AutoPrune }
162 If AutoPrune is set to {\bf yes} (default), Bacula
163 will automatically apply the Volume retention period when running a Job and
164 it needs a new Volume but no appendable volumes are available. At that point,
165 Bacula will prune all Volumes that can be pruned (i.e. AutoPrune set) in an
166 attempt to find a usable volume. If during the autoprune, all files are
167 pruned from the Volume, it will be marked with VolStatus {\bf Purged}. The
168 default is {\bf yes}. Note, that although the File and Job records may be
169 pruned from the catalog, a Volume will be marked Purged (and hence
170 ready for recycling) if the Volume status is Append, Full, Used, or Error.
171 If the Volume has another status, such as Archive, Read-Only, Disabled,
172 Busy, or Cleaning, the Volume status will not be changed to Purged.
174 \item [Volume Retention = \lt{}time-period-specification\gt{}]
175 \index[console]{Volume Retention}
176 The Volume Retention record defines the length of time that Bacula will
177 guarantee that the Volume is not reused counting from the time the last
178 job stored on the Volume terminated. A key point is that this time
179 period is not even considered as long at the Volume remains appendable.
180 The Volume Retention period count down begins only when the Append
181 status has been changed to some othe status (Full, Used, Purged, ...).
183 When this time period expires, and if {\bf AutoPrune} is set to {\bf
184 yes}, and a new Volume is needed, but no appendable Volume is available,
185 Bacula will prune (remove) Job records that are older than the specified
186 Volume Retention period.
188 The Volume Retention period takes precedence over any Job Retention
189 period you have specified in the Client resource. It should also be
190 noted, that the Volume Retention period is obtained by reading the
191 Catalog Database Media record rather than the Pool resource record.
192 This means that if you change the VolumeRetention in the Pool resource
193 record, you must ensure that the corresponding change is made in the
194 catalog by using the {\bf update pool} command. Doing so will insure
195 that any new Volumes will be created with the changed Volume Retention
196 period. Any existing Volumes will have their own copy of the Volume
197 Retention period that can only be changed on a Volume by Volume basis
198 using the {\bf update volume} command.
200 When all file catalog entries are removed from the volume, its VolStatus is
201 set to {\bf Purged}. The files remain physically on the Volume until the
202 volume is overwritten.
204 Retention periods are specified in seconds, minutes, hours, days, weeks,
205 months, quarters, or years on the record. See the
206 \ilink{Configuration chapter}{Time} of this manual for
207 additional details of time specification.
209 The default is 1 year.
211 \item [Recycle = \lt{}yes|no\gt{}]
213 This statement tells Bacula whether or not the particular Volume can be
214 recycled (i.e. rewritten). If Recycle is set to {\bf no} (the
215 default), then even if Bacula prunes all the Jobs on the volume and it
216 is marked {\bf Purged}, it will not consider the tape for recycling. If
217 Recycle is set to {\bf yes} and all Jobs have been pruned, the volume
218 status will be set to {\bf Purged} and the volume may then be reused
219 when another volume is needed. If the volume is reused, it is relabeled
220 with the same Volume Name, however all previous data will be lost.
223 It is also possible to "force" pruning of all Volumes in the Pool
224 associated with a Job by adding {\bf Prune Files = yes} to the Job resource.
227 \subsection*{Recycling Algorithm}
228 \index[general]{Algorithm!Recycling }
229 \index[general]{Recycling Algorithm }
230 \addcontentsline{toc}{subsection}{Recycling Algorithm}
232 After all Volumes of a Pool have been pruned (as mentioned above, this happens
233 when a Job needs a new Volume and no appendable Volumes are available), Bacula
234 will look for the oldest Volume that is Purged (all Jobs and Files expired),
235 and if the {\bf Recycle} flag is on (Recycle=yes) for that Volume, Bacula will
236 relabel it and write new data on it.
238 As mentioned above, there are two key points for getting a Volume
239 to be recycled. First, the Volume must no longer be marked Append (there
240 are a number of directives to automatically make this change), and second
241 since the last write on the Volume, one or more of the Retention periods
242 must have expired so that there are no more catalog backup job records
243 that reference that Volume. Once both those conditions are satisfied,
244 the volume can be marked Purged and hence recycled.
246 The full algorithm that Bacula uses when it needs a new Volume is:
249 \item Search the Pool for a Volume with VolStatus=Append (if there is more
250 than one, the Volume with the oldest date last written is chosen. If
251 two have the same date then the one with the lowest MediaId is chosen).
252 \item Search the Pool for a Volume with VolStatus=Recycle and the InChanger
253 flag is set true (if there is more than one, the Volume with the oldest
254 date last written is chosen. If two have the same date then the one
255 with the lowest MediaId is chosen).
256 \item Try recycling any purged Volumes.
257 \item Prune volumes applying Volume retention period (Volumes with VolStatus
258 Full, Used, or Append are pruned).
259 \item Search the Pool for a Volume with VolStatus=Purged
260 \item If InChanger was set, go back to the first step above, but
261 this second time, ignore the InChanger flag in step 2.
262 \item If a Pool named "Scratch" exists, search for a Volume and if found
263 move it to the current Pool for the Job and use it.
264 \item Attempt to create a new Volume if automatic labeling enabled
265 If Python is enabled, a Python NewVolume even is generated before
266 the Label Format check is used.
267 \item Prune the oldest Volume if RecycleOldestVolume=yes (the Volume with the
268 oldest LastWritten date and VolStatus equal to Full, Recycle, Purged, Used,
269 or Append is chosen). This record ensures that all retention periods are
271 \item Purge the oldest Volume if PurgeOldestVolume=yes (the Volume with the
272 oldest LastWritten date and VolStatus equal to Full, Recycle, Purged, Used,
273 or Append is chosen). We strongly recommend against the use of {\bf
274 PurgeOldestVolume} as it can quite easily lead to loss of current backup
276 \item Give up and ask operator.
279 The above occurs when Bacula has finished writing a Volume or when no Volume
280 is present in the drive.
282 On the other hand, if you have inserted a different Volume after the last job,
283 and Bacula recognizes the Volume as valid, it will request authorization from
284 the Director to use this Volume. In this case, if you have set {\bf Recycle
285 Current Volume = yes} and the Volume is marked as Used or Full, Bacula will
286 prune the volume and if all jobs were removed during the pruning (respecting
287 the retention periods), the Volume will be recycled and used.
288 The recycling algorithm in this case is:
291 \item If the VolStatus is {\bf Append} or {\bf Recycle} and {\bf Accept Any
292 Volume} is set, the volume will be used.
293 \item If {\bf Recycle Current Volume} is set and the volume is marked {\bf
294 Full} or {\bf Used}, Bacula will prune the volume (applying the retention
295 period). If all Jobs are pruned from the volume, it will be recycled.
298 This permits users to manually change the Volume every day and load tapes in
299 an order different from what is in the catalog, and if the volume does not
300 contain a current copy of your backup data, it will be used.
302 \subsection*{Recycle Status}
303 \index[general]{Status!Recycle }
304 \index[general]{Recycle Status }
305 \addcontentsline{toc}{subsection}{Recycle Status}
307 Each Volume inherits the Recycle status (yes or no) from the Pool resource
308 record when the Media record is created (normally when the Volume is labeled).
309 This Recycle status is stored in the Media record of the Catalog. Using
310 the Console program, you may subsequently change the Recycle status for each
311 Volume. For example in the following output from {\bf list volumes}:
315 +----------+-------+--------+---------+------------+--------+-----+
316 | VolumeNa | Media | VolSta | VolByte | LastWritte | VolRet | Rec |
317 +----------+-------+--------+---------+------------+--------+-----+
318 | File0001 | File | Full | 4190055 | 2002-05-25 | 14400 | 1 |
319 | File0002 | File | Full | 1896460 | 2002-05-26 | 14400 | 1 |
320 | File0003 | File | Full | 1896460 | 2002-05-26 | 14400 | 1 |
321 | File0004 | File | Full | 1896460 | 2002-05-26 | 14400 | 1 |
322 | File0005 | File | Full | 1896460 | 2002-05-26 | 14400 | 1 |
323 | File0006 | File | Full | 1896460 | 2002-05-26 | 14400 | 1 |
324 | File0007 | File | Purged | 1896466 | 2002-05-26 | 14400 | 1 |
325 +----------+-------+--------+---------+------------+--------+-----+
329 all the volumes are marked as recyclable, and the last Volume, {\bf File0007}
330 has been purged, so it may be immediately recycled. The other volumes are all
331 marked recyclable and when their Volume Retention period (14400 seconds or 4
332 hours) expires, they will be eligible for pruning, and possibly recycling.
333 Even though Volume {\bf File0007} has been purged, all the data on the Volume
334 is still recoverable. A purged Volume simply means that there are no entries
335 in the Catalog. Even if the Volume Status is changed to {\bf Recycle}, the
336 data on the Volume will be recoverable. The data is lost only when the Volume
337 is re-labeled and re-written.
339 To modify Volume {\bf File0001} so that it cannot be recycled, you use the
340 {\bf update volume pool=File} command in the console program, or simply {\bf
341 update} and Bacula will prompt you for the information.
345 +----------+------+-------+---------+-------------+-------+-----+
346 | VolumeNa | Media| VolSta| VolByte | LastWritten | VolRet| Rec |
347 +----------+------+-------+---------+-------------+-------+-----+
348 | File0001 | File | Full | 4190055 | 2002-05-25 | 14400 | 0 |
349 | File0002 | File | Full | 1897236 | 2002-05-26 | 14400 | 1 |
350 | File0003 | File | Full | 1896460 | 2002-05-26 | 14400 | 1 |
351 | File0004 | File | Full | 1896460 | 2002-05-26 | 14400 | 1 |
352 | File0005 | File | Full | 1896460 | 2002-05-26 | 14400 | 1 |
353 | File0006 | File | Full | 1896460 | 2002-05-26 | 14400 | 1 |
354 | File0007 | File | Purged| 1896466 | 2002-05-26 | 14400 | 1 |
355 +----------+------+-------+---------+-------------+-------+-----+
359 In this case, {\bf File0001} will never be automatically recycled. The same
360 effect can be achieved by setting the Volume Status to Read-Only.
362 \subsection*{Making Bacula Use a Single Tape}
364 \index[general]{Tape!Making Bacula Use a Single}
365 \index[general]{Making Bacula Use a Single Tape}
366 \addcontentsline{toc}{subsection}{Making Bacula Use a Single Tape}
368 Most people will want Bacula to fill a tape and when it is full, a new tape
369 will be mounted, and so on. However, as an extreme example, it is possible for
370 Bacula to write on a single tape, and every night to rewrite it. To get this
371 to work, you must do two things: first, set the VolumeRetention to less than
372 your save period (one day), and the second item is to make Bacula mark the
373 tape as full after using it once. This is done using {\bf UseVolumeOnce =
374 yes}. If this latter record is not used and the tape is not full after the
375 first time it is written, Bacula will simply append to the tape and eventually
376 request another volume. Using the tape only once, forces the tape to be marked
377 {\bf Full} after each use, and the next time {\bf Bacula} runs, it will
380 An example Pool resource that does this is:
386 Use Volume Once = yes
389 VolumeRetention = 12h # expire after 12 hours
395 \subsection*{A Daily, Weekly, Monthly Tape Usage Example}
397 \index[general]{Daily, Weekly, Monthly Tape Usage Example }
398 \index[general]{Example!Daily Weekly Monthly Tape Usage }
399 \addcontentsline{toc}{subsection}{Daily, Weekly, Monthly Tape Usage Example}
401 This example is meant to show you how one could define a fixed set of volumes
402 that Bacula will rotate through on a regular schedule. There are an infinite
403 number of such schemes, all of which have various advantages and
406 We start with the following assumptions:
409 \item A single tape has more than enough capacity to do a full save.
410 \item There are 10 tapes that are used on a daily basis for incremental
411 backups. They are prelabeled Daily1 ... Daily10.
412 \item There are 4 tapes that are used on a weekly basis for full backups.
413 They are labeled Week1 ... Week4.
414 \item There are 12 tapes that are used on a monthly basis for full backups.
415 They are numbered Month1 ... Month12
416 \item A full backup is done every Saturday evening (tape inserted Friday
417 evening before leaving work).
418 \item No backups are done over the weekend (this is easy to change).
419 \item The first Friday of each month, a Monthly tape is used for the Full
421 \item Incremental backups are done Monday - Friday (actually Tue-Fri
425 We start the system by doing a Full save to one of the weekly volumes or one
426 of the monthly volumes. The next morning, we remove the tape and insert a
427 Daily tape. Friday evening, we remove the Daily tape and insert the next tape
428 in the Weekly series. Monday, we remove the Weekly tape and re-insert the
429 Daily tape. On the first Friday of the next month, we insert the next Monthly
430 tape in the series rather than a Weekly tape, then continue. When a Daily tape
431 finally fills up, {\bf Bacula} will request the next one in the series, and
432 the next day when you notice the email message, you will mount it and {\bf
433 Bacula} will finish the unfinished incremental backup.
435 What does this give? Well, at any point, you will have the last complete
436 Full save plus several Incremental saves. For any given file you want to
437 recover (or your whole system), you will have a copy of that file every day
438 for at least the last 14 days. For older versions, you will have at least 3
439 and probably 4 Friday full saves of that file, and going back further, you
440 will have a copy of that file made on the beginning of the month for at least
443 So you have copies of any file (or your whole system) for at least a year, but
444 as you go back in time, the time between copies increases from daily to weekly
447 What would the Bacula configuration look like to implement such a scheme?
453 Run = Level=Full Pool=Monthly 1st sat at 03:05
454 Run = Level=Full Pool=Weekly 2nd-5th sat at 03:05
455 Run = Level=Incremental Pool=Daily tue-fri at 03:05
461 Client = LocalMachine
466 Schedule = "NightlySave"
468 # Definition of file storage device
473 Password = XXXXXXXXXXXXX
479 Include = signature=MD5 {
488 VolumeRetention = 10d # recycle in 10 days
494 Use Volume Once = yes
497 VolumeRetention = 30d # recycle in 30 days (default)
502 Use Volume Once = yes
505 VolumeRetention = 365d # recycle in 1 year
511 \subsection*{ Automatic Pruning and Recycling Example}
512 \label{PruningExample}
513 \index[general]{Automatic Pruning and Recycling Example }
514 \index[general]{Example!Automatic Pruning and Recycling }
515 \addcontentsline{toc}{subsection}{Automatic Pruning and Recycling Example}
517 Perhaps the best way to understand the various resource records that come into
518 play during automatic pruning and recycling is to run a Job that goes through
519 the whole cycle. If you add the following resources to your Director's
525 Name = "30 minute cycle"
526 Run = Level=Full Pool=File Messages=Standard Storage=File
528 Run = Level=Full Pool=File Messages=Standard Storage=File
540 Schedule = "30 minute cycle"
542 # Definition of file storage device
545 Address = XXXXXXXXXXX
547 Password = XXXXXXXXXXXXX
553 Include = signature=MD5 {
560 Use Volume Once = yes
571 Where you will need to replace the {\bf ffffffffff}'s by the appropriate files
572 to be saved for your configuration. For the FileSet Include, choose a
573 directory that has one or two megabytes maximum since there will probably be
574 approximately 8 copies of the directory that {\bf Bacula} will cycle through.
576 In addition, you will need to add the following to your Storage daemon's
584 Archive Device = /tmp
587 AutomaticMount = yes;
594 With the above resources, Bacula will start a Job every half hour that saves a
595 copy of the directory you chose to /tmp/File0001 ... /tmp/File0012. After 4
596 hours, Bacula will start recycling the backup Volumes (/tmp/File0001 ...). You
597 should see this happening in the output produced. Bacula will automatically
598 create the Volumes (Files) the first time it uses them.
600 To turn it off, either delete all the resources you've added, or simply
601 comment out the {\bf Schedule} record in the {\bf Job} resource.
603 \subsection*{Manually Recycling Volumes}
604 \label{manualrecycling}
605 \index[general]{Volumes!Manually Recycling }
606 \index[general]{Manually Recycling Volumes }
607 \addcontentsline{toc}{subsection}{Manually Recycling Volumes}
609 Although automatic recycling of Volumes is implemented in version 1.20 and
611 \ilink{Automatic Recycling of Volumes}{_ChapterStart22} chapter of
612 this manual), you may want to manually force reuse (recycling) of a Volume.
614 Assuming that you want to keep the Volume name, but you simply want to write
615 new data on the tape, the steps to take are:
618 \item Use the {\bf update volume} command in the Console to ensure that the
619 {\bf Recycle} field is set to {\bf 1}
620 \item Use the {\bf purge jobs volume} command in the Console to mark the
621 Volume as {\bf Purged}. Check by using {\bf list volumes}.
624 Once the Volume is marked Purged, it will be recycled the next time a Volume
627 If you wish to reuse the tape by giving it a new name, follow the following
631 \item Use the {\bf purge jobs volume} command in the Console to mark the
632 Volume as {\bf Purged}. Check by using {\bf list volumes}.
633 \item In Bacula version 1.30 or greater, use the Console {\bf relabel}
634 command to relabel the Volume.
637 Please note that the relabel command applies only to tape Volumes.
639 For Bacula versions prior to 1.30 or to manually relabel the Volume, use the
643 \item Use the {\bf delete volume} command in the Console to delete the Volume
645 \item If a different tape is mounted, use the {\bf unmount} command,
646 remove the tape, and insert the tape to be renamed.
647 \item Write an EOF mark in the tape using the following commands:
651 mt -f /dev/nst0 rewind
656 where you replace {\bf /dev/nst0} with the appropriate device name on your
658 \item Use the {\bf label} command to write a new label to the tape and to
659 enter it in the catalog.
662 Please be aware that the {\bf delete} command can be dangerous. Once it is
663 done, to recover the File records, you must either restore your database as it
664 was before the {\bf delete} command, or use the {\bf bscan} utility program to
665 scan the tape and recreate the database entries.