4 \chapter{What is Bacula?}
6 \index[general]{Bacula!What is }
7 \index[general]{What is Bacula? }
9 Bacula is a set of computer programs that permits the system
10 administrator to manage backup, recovery, and verification of computer data
11 across a network of computers of different kinds. Bacula can also run entirely
12 upon a single computer and can backup to various types of media, including tape
15 In technical terms, it is a
16 network Client/Server based backup program. Bacula is relatively easy to use
17 and efficient, while offering many advanced storage management features that
18 make it easy to find and recover lost or damaged files. Due to its modular
19 design, Bacula is scalable from small single computer systems to systems
20 consisting of hundreds of computers located over a large network.
22 \section{Who Needs Bacula?}
23 \index[general]{Who Needs Bacula? }
24 \index[general]{Bacula!Who Needs }
26 If you are currently using a program such as tar, dump, or
27 bru to backup your computer data, and you would like a network solution, more
28 flexibility, or catalog services, Bacula will most likely provide the
29 additional features you want. However, if you are new to Unix systems or do
30 not have offsetting experience with a sophisticated backup package, the Bacula project does not
31 recommend using Bacula as it is much more difficult to setup and use than
34 If you want Bacula to behave like the above mentioned simple
35 programs and write over any tape that you put in the drive, then you will find
36 working with Bacula difficult. Bacula is designed to protect your data
37 following the rules you specify, and this means reusing a tape only
38 as the last resort. It is possible to "force" Bacula to write
39 over any tape in the drive, but it is easier and more efficient to use a
40 simpler program for that kind of operation.
42 If you would like a backup program that can write
43 to multiple volumes (i.e. is not limited by your tape drive capacity), Bacula
44 can most likely fill your needs. In addition, quite a number of Bacula users
45 report that Bacula is simpler to setup and use than other equivalent programs.
47 If you are currently using a sophisticated commercial package such as Legato
48 Networker. ARCserveIT, Arkeia, or PerfectBackup+, you may be interested in
49 Bacula, which provides many of the same features and is free software
50 available under the Affero GPL Version 3 software license.
52 \section{Bacula Components or Services}
53 \index[general]{Bacula Components or Services }
54 \index[general]{Services!Bacula Components or }
56 Bacula is made up of the following five major components or services:
57 Director, Console, File, Storage, and Monitor services.
60 \addcontentsline{lof}{figure}{Bacula Applications}
62 \includegraphics[width=0.8\linewidth]{bacula-applications}
64 (thanks to Aristedes Maniatis for this graphic and the one below)
65 % TODO: move the thanks to Credits section in preface
67 \subsection*{Bacula Director}
69 The Bacula Director service is the program that supervises
70 all the backup, restore, verify and archive operations. The system
71 administrator uses the Bacula Director to schedule backups and to
72 recover files. For more details see the Director Services Daemon Design
73 Document in the Bacula Developer's Guide. The Director runs as a daemon
74 (or service) in the background.
75 % TODO: tell reader where this Developer's Guide is at?
78 \subsection*{Bacula Console}
80 The Bacula Console service is the program that allows the
81 administrator or user to communicate with the Bacula Director
82 Currently, the Bacula Console is available in three versions:
83 text-based console interface, QT-based interface, and a
84 wxWidgets graphical interface.
85 The first and simplest is to run the Console program in a shell window
86 (i.e. TTY interface). Most system administrators will find this
87 completely adequate. The second version is a GNOME GUI interface that
88 is far from complete, but quite functional as it has most the
89 capabilities of the shell Console. The third version is a wxWidgets GUI
90 with an interactive file restore. It also has most of the capabilities
91 of the shell console, allows command completion with tabulation, and
92 gives you instant help about the command you are typing. For more
93 details see the \borgxrlinkdocument{Bacula Console Design Document}{TheConsoleChapter}{console}{Chapter}.
95 \subsection*{Bacula File}
97 The Bacula File service (also known as the Client program) is the software
98 program that is installed on the machine to be backed up.
100 operating system on which it runs and is responsible for providing the
101 file attributes and data when requested by the Director. The File
102 services are also responsible for the file system dependent part of
103 restoring the file attributes and data during a recovery operation. For
104 more details see the File Services Daemon Design Document in the Bacula
105 Developer's Guide. This program runs as a daemon on the machine to be
107 In addition to Unix/Linux File daemons, there is a Windows File daemon
108 (normally distributed in binary format). The Windows File daemon runs
109 on current Windows versions (NT, 2000, XP, 2003, and possibly Me and
111 % TODO: maybe do not list Windows here as that is listed elsewhere
112 % TODO: remove "possibly"?
113 % TODO: mention Vista?
115 \subsection*{Bacula Storage}
117 The Bacula Storage services consist of the software programs that
118 perform the storage and recovery of the file attributes and data to the
119 physical backup media or volumes. In other words, the Storage daemon is
120 responsible for reading and writing your tapes (or other storage media,
121 e.g. files). For more details see the Storage Services Daemon Design
122 Document in the Bacula Developer's Guide. The Storage services runs as
123 a daemon on the machine that has the backup device (usually a tape
125 % TODO: may switch e.g. to "for example" or "such as" as appropriate
126 % TODO: is "usually" correct? Maybe "such as" instead?
128 \subsection*{Catalog}
130 The Catalog services are comprised of the software programs
131 responsible for maintaining the file indexes and volume databases for
132 all files backed up. The Catalog services permit the system
133 administrator or user to quickly locate and restore any desired file.
134 The Catalog services sets Bacula apart from simple backup programs like
135 tar and bru, because the catalog maintains a record of all Volumes used,
136 all Jobs run, and all Files saved, permitting efficient restoration and
137 Volume management. Bacula currently supports three different databases,
138 MySQL, PostgreSQL, and SQLite, one of which must be chosen when building
141 The three SQL databases currently supported (MySQL, PostgreSQL or
142 SQLite) provide quite a number of features, including rapid indexing,
143 arbitrary queries, and security. Although the Bacula project plans to support other
144 major SQL databases, the current Bacula implementation interfaces only
145 to MySQL, PostgreSQL and SQLite. For the technical and porting details
146 see the Catalog Services Design Document in the developer's documented.
148 The packages for MySQL and PostgreSQL are available for several operating
150 Alternatively, installing from the
151 source is quite easy, see the \ilink{Installing and Configuring MySQL}{MySqlChapter} chapter of this document for the details. For
152 more information on MySQL, please see:
153 \elink{www.mysql.com}{http://www.mysql.com}. Or see the \ilink{Installing and Configuring PostgreSQL}{PostgreSqlChapter} chapter of this
154 document for the details. For more information on PostgreSQL, please
155 see: \elink{www.postgresql.org}{http://www.postgresql.org}.
157 Configuring and building SQLite is even easier. For the details of
158 configuring SQLite, please see the \ilink{Installing and Configuring SQLite}{SqlLiteChapter} chapter of this document.
160 \subsection*{Bacula Monitor}
162 A Bacula Monitor service is the program that allows the
163 administrator or user to watch current status of Bacula Directors,
164 Bacula File Daemons and Bacula Storage Daemons.
165 Currently, only a GTK+ version is available, which works with GNOME,
166 KDE, or any window manager that supports the FreeDesktop.org system tray
169 To perform a successful save or restore, the following four daemons must be
170 configured and running: the Director daemon, the File daemon, the Storage
171 daemon, and the Catalog service (MySQL, PostgreSQL or SQLite).
173 \section{Bacula Configuration}
174 \index[general]{Configuration!Bacula }
175 \index[general]{Bacula Configuration }
177 In order for Bacula to understand your system, what clients you want backed
178 up and how, you must create a number of configuration files containing
179 resources (or objects). The following presents an overall picture of this:
181 \addcontentsline{lof}{figure}{Bacula Objects}
183 \includegraphics[width=0.8\linewidth]{bacula-objects}
186 \section{Conventions Used in this Document}
187 \index[general]{Conventions Used in this Document }
188 \index[general]{Document!Conventions Used in this }
190 Bacula is in a state of evolution, and as a consequence, this manual
191 will not always agree with the code. If an item in this manual is preceded by
192 an asterisk (*), it indicates that the particular feature is not implemented.
193 If it is preceded by a plus sign (+), it indicates that the feature may be
194 partially implemented.
195 % TODO: search for plus sign and asterisk and "IMPLEMENTED" and fix for printed book
197 If you are reading this manual as supplied in a released version of the
198 software, the above paragraph holds true. If you are reading the online
199 version of the manual,
200 \elink{www.bacula.org}{http://www.bacula.org}, please bear in
201 mind that this version describes the current version in development (in the
202 CVS) that may contain features not in the released version. Just the same, it
203 generally lags behind the code a bit.
204 % TODO: is this still true? there are separate websites
206 \section{Quick Start}
207 \index[general]{Quick Start }
208 \index[general]{Start!Quick }
210 To get Bacula up and running quickly, the author recommends
211 that you first scan the
212 Terminology section below, then quickly review the next chapter entitled
213 \ilink{The Current State of Bacula}{StateChapter}, then the
214 \ilink{Getting Started with Bacula}{QuickStartChapter}, which will
215 give you a quick overview of getting Bacula running. After which, you should
216 proceed to the chapter on
217 \ilink{Installing Bacula}{InstallChapter}, then
218 \ilink{How to Configure Bacula}{ConfigureChapter}, and finally the
220 \ilink{Running Bacula}{TutorialChapter}.
222 \section{Terminology}
223 \index[general]{Terminology }
227 \item [Administrator]
228 \index[fd]{Administrator }
229 The person or persons responsible for administrating the Bacula system.
233 The term Backup refers to a Bacula Job that saves files.
235 \item [Bootstrap File]
236 \index[fd]{Bootstrap File }
237 The bootstrap file is an ASCII file containing a compact form of
238 commands that allow Bacula or the stand-alone file extraction utility
239 (bextract) to restore the contents of one or more Volumes, for
240 example, the current state of a system just backed up. With a bootstrap
241 file, Bacula can restore your system without a Catalog. You can create
242 a bootstrap file from a Catalog to extract any file or files you wish.
246 The Catalog is used to store summary information about the Jobs,
247 Clients, and Files that were backed up and on what Volume or Volumes.
248 The information saved in the Catalog permits the administrator or user
249 to determine what jobs were run, their status as well as the important
250 characteristics of each file that was backed up, and most importantly,
251 it permits you to choose what files to restore.
253 online resource, but does not contain the data for the files backed up.
254 Most of the information stored in the catalog is also stored on the
255 backup volumes (i.e. tapes). Of course, the tapes will also have a
256 copy of the file data in addition to the File Attributes (see below).
258 The catalog feature is one part of Bacula that distinguishes it from
259 simple backup and archive programs such as dump and tar.
263 In Bacula's terminology, the word Client refers to the machine being
264 backed up, and it is synonymous with the File services or File daemon,
265 and quite often, it is referred to it as the FD. A Client is defined in a
266 configuration file resource.
270 The program that interfaces to the Director allowing the user or system
271 administrator to control Bacula.
275 Unix terminology for a program that is always present in the background to
276 carry out a designated task. On Windows systems, as well as some Unix
277 systems, daemons are called Services.
280 \index[fd]{Directive }
281 The term directive is used to refer to a statement or a record within a
282 Resource in a configuration file that defines one specific setting. For
283 example, the {\bf Name} directive defines the name of the Resource.
286 \index[fd]{Director }
287 The main Bacula server daemon that schedules and directs all Bacula
288 operations. Occasionally, the project refers to the Director as DIR.
291 \index[fd]{Differential }
292 A backup that includes all files changed since the last Full save started.
293 Note, other backup programs may define this differently.
295 \item [File Attributes]
296 \index[fd]{File Attributes }
297 The File Attributes are all the information necessary about a file to
298 identify it and all its properties such as size, creation date, modification
299 date, permissions, etc. Normally, the attributes are handled entirely by
300 Bacula so that the user never needs to be concerned about them. The
301 attributes do not include the file's data.
304 \index[fd]{File Daemon }
305 The daemon running on the client computer to be backed up. This is also
306 referred to as the File services, and sometimes as the Client services or the
312 A FileSet is a Resource contained in a configuration file that defines
313 the files to be backed up. It consists of a list of included files or
314 directories, a list of excluded files, and how the file is to be stored
315 (compression, encryption, signatures). For more details, see the
316 \ilink{FileSet Resource definition}{FileSetResource} in the Director
317 chapter of this document.
320 \index[fd]{Incremental }
321 A backup that includes all files changed since the last Full, Differential,
322 or Incremental backup started. It is normally specified on the {\bf Level}
323 directive within the Job resource definition, or in a Schedule resource.
328 A Bacula Job is a configuration resource that defines the work that
329 Bacula must perform to backup or restore a particular Client. It
330 consists of the {\bf Type} (backup, restore, verify, etc), the {\bf
331 Level} (full, incremental,...), the {\bf FileSet}, and {\bf Storage} the
332 files are to be backed up (Storage device, Media Pool). For more
333 details, see the \ilink{Job Resource definition}{JobResource} in the
334 Director chapter of this document.
335 % TODO: clean up "..." for book
339 The program that interfaces to all the daemons allowing the user or
340 system administrator to monitor Bacula status.
343 \index[fd]{Resource }
344 A resource is a part of a configuration file that defines a specific
345 unit of information that is available to Bacula. It consists of several
346 directives (individual configuration statements). For example, the {\bf
347 Job} resource defines all the properties of a specific Job: name,
348 schedule, Volume pool, backup type, backup level, ...
349 % TODO: clean up "..." for book
353 A restore is a configuration resource that describes the operation of
354 recovering a file from backup media. It is the inverse of a save,
355 except that in most cases, a restore will normally have a small set of
356 files to restore, while normally a Save backs up all the files on the
357 system. Of course, after a disk crash, Bacula can be called upon to do
358 a full Restore of all files that were on the system.
359 % TODO: Why? Why say "Of course"??
361 % TODO: define "Save"
362 % TODO: define "Full"
365 \index[fd]{Schedule }
366 A Schedule is a configuration resource that defines when the Bacula Job
367 will be scheduled for execution. To use the Schedule, the Job resource
368 will refer to the name of the Schedule. For more details, see the
369 \ilink{Schedule Resource definition}{ScheduleResource} in the Director
370 chapter of this document.
374 This is a program that remains permanently in memory awaiting
375 instructions. In Unix environments, services are also known as
378 \item [Storage Coordinates]
379 \index[fd]{Storage Coordinates }
380 The information returned from the Storage Services that uniquely locates
381 a file on a backup medium. It consists of two parts: one part pertains
382 to each file saved, and the other part pertains to the whole Job.
383 Normally, this information is saved in the Catalog so that the user
384 doesn't need specific knowledge of the Storage Coordinates. The Storage
385 Coordinates include the File Attributes (see above) plus the unique
386 location of the information on the backup Volume.
388 \item [Storage Daemon]
389 \index[fd]{Storage Daemon }
390 The Storage daemon, sometimes referred to as the SD, is the code that
391 writes the attributes and data to a storage Volume (usually a tape or
396 Normally refers to the internal conversation between the File daemon and
397 the Storage daemon. The File daemon opens a {\bf session} with the
398 Storage daemon to save a FileSet or to restore it. A session has a
399 one-to-one correspondence to a Bacula Job (see above).
403 A verify is a job that compares the current file attributes to the
404 attributes that have previously been stored in the Bacula Catalog. This
405 feature can be used for detecting changes to critical system files
406 similar to what a file integrity checker like Tripwire does.
407 One of the major advantages of
408 using Bacula to do this is that on the machine you want protected such
409 as a server, you can run just the File daemon, and the Director, Storage
410 daemon, and Catalog reside on a different machine. As a consequence, if
411 your server is ever compromised, it is unlikely that your verification
412 database will be tampered with.
414 Verify can also be used to check that the most recent Job data written
415 to a Volume agrees with what is stored in the Catalog (i.e. it compares
416 the file attributes), *or it can check the Volume contents against the
417 original files on disk.
420 \index[fd]{*Archive }
421 An Archive operation is done after a Save, and it consists of removing the
422 Volumes on which data is saved from active use. These Volumes are marked as
423 Archived, and may no longer be used to save files. All the files contained
424 on an Archived Volume are removed from the Catalog. NOT YET IMPLEMENTED.
426 \item [Retention Period]
427 \index[fd]{Retention Period }
428 There are various kinds of retention periods that Bacula recognizes.
429 The most important are the {\bf File} Retention Period, {\bf Job}
430 Retention Period, and the {\bf Volume} Retention Period. Each of these
431 retention periods applies to the time that specific records will be kept
432 in the Catalog database. This should not be confused with the time that
433 the data saved to a Volume is valid.
435 The File Retention Period determines the time that File records are kept
436 in the catalog database. This period is important for two reasons: the
437 first is that as long as File records remain in the database, you
438 can "browse" the database with a console program and restore any
439 individual file. Once the File records are removed or pruned from the
440 database, the individual files of a backup job can no longer be
441 "browsed". The second reason for carefully choosing the File Retention
442 Period is because the volume of
443 the database File records use the most storage space in the
444 database. As a consequence, you must ensure that regular "pruning" of
445 the database file records is done to keep your database from growing
446 too large. (See the Console {\bf prune}
447 command for more details on this subject).
449 The Job Retention Period is the length of time that Job records will be
450 kept in the database. Note, all the File records are tied to the Job
451 that saved those files. The File records can be purged leaving the Job
452 records. In this case, information will be available about the jobs
453 that ran, but not the details of the files that were backed up.
454 Normally, when a Job record is purged, all its File records will also be
457 The Volume Retention Period is the minimum of time that a Volume will be
458 kept before it is reused. Bacula will normally never overwrite a Volume
459 that contains the only backup copy of a file. Under ideal conditions,
460 the Catalog would retain entries for all files backed up for all current
461 Volumes. Once a Volume is overwritten, the files that were backed up on
462 that Volume are automatically removed from the Catalog. However, if
463 there is a very large pool of Volumes or a Volume is never overwritten,
464 the Catalog database may become enormous. To keep the Catalog to a
465 manageable size, the backup information should be removed from the
466 Catalog after the defined File Retention Period. Bacula provides the
467 mechanisms for the catalog to be automatically pruned according to the
468 retention periods defined.
472 A Scan operation causes the contents of a Volume or a series of Volumes
473 to be scanned. These Volumes with the information on which files they
474 contain are restored to the Bacula Catalog. Once the information is
475 restored to the Catalog, the files contained on those Volumes may be
476 easily restored. This function is particularly useful if certain
477 Volumes or Jobs have exceeded their retention period and have been
478 pruned or purged from the Catalog. Scanning data from Volumes into the
479 Catalog is done by using the {\bf bscan} program. See the \borgxrlink{bscan}{bscan}{utility}{section} of the \utilityman{} for more
484 A Volume is an archive unit, normally a tape or a named disk file where
485 Bacula stores the data from one or more backup jobs. All Bacula Volumes
486 have a software label written to the Volume by Bacula so that it
487 identifies what Volume it is really reading. (Normally there should be
488 no confusion with disk files, but with tapes, it is easy to mount the
492 \section{What Bacula is Not}
493 \index[general]{What Bacula is Not}
495 Bacula is a backup, restore and verification program and is not a
496 complete disaster recovery system in itself, but it can be a key part of one
497 if you plan carefully and follow the instructions included in the
498 \ilink{Disaster Recovery}{RescueChapter} Chapter of this manual.
500 With proper planning, as mentioned in the Disaster Recovery chapter,
501 Bacula can be a central component of your disaster recovery system. For
502 example, if you have created an emergency boot disk, and/or a Bacula Rescue disk to
503 save the current partitioning information of your hard disk, and maintain a
504 complete Bacula backup, it is possible to completely recover your system from
505 "bare metal" that is starting from an empty disk.
507 If you have used the {\bf WriteBootstrap} record in your job or some other
508 means to save a valid bootstrap file, you will be able to use it to extract
509 the necessary files (without using the catalog or manually searching for the
512 \section{Interactions Between the Bacula Services}
513 \index[general]{Interactions Between the Bacula Services}
514 \index[general]{Services!Interactions Between the Bacula}
516 The following block diagram shows the typical interactions between the Bacula
517 Services for a backup job. Each block represents in general a separate process
518 (normally a daemon). In general, the Director oversees the flow of
519 information. It also maintains the Catalog.
521 \addcontentsline{lof}{figure}{Interactions between Bacula Services}
523 \includegraphics[width=0.8\linewidth]{flow}
projects / bacula / docs / blob