What is Bacula?
Bacula is a set of computer programs that permits the system
administrator to manage backup, recovery, and verification of computer data
across a network of computers of different kinds. Bacula can also run entirely
upon a single computer and can backup to various types of media, including tape
In technical terms, it is a
network Client/Server based backup program. Bacula is relatively easy to use
and efficient, while offering many advanced storage management features that
make it easy to find and recover lost or damaged files. Due to its modular
design, Bacula is scalable from small single computer systems to systems
consisting of hundreds of computers located over a large network.
If you are currently using a program such as tar, dump, or
bru to backup your computer data, and you would like a network solution, more
flexibility, or catalog services, Bacula will most likely provide the
additional features you want. However, if you are new to Unix systems or do
not have offsetting experience with a sophisticated backup package, the Bacula project does not
recommend using Bacula as it is much more difficult to setup and use than
tar or dump.
If you want Bacula to behave like the above mentioned simple
programs and write over any tape that you put in the drive, then you will find
working with Bacula difficult. Bacula is designed to protect your data
following the rules you specify, and this means reusing a tape only
as the last resort. It is possible to "force" Bacula to write
over any tape in the drive, but it is easier and more efficient to use a
simpler program for that kind of operation.
If you would like a backup program that can write
to multiple volumes (i.e. is not limited by your tape drive capacity), Bacula
can most likely fill your needs. In addition, quite a number of Bacula users
report that Bacula is simpler to setup and use than other equivalent programs.
If you are currently using a sophisticated commercial package such as Legato
Networker. ARCserveIT, Arkeia, or PerfectBackup+, you may be interested in
Bacula, which provides many of the same features and is free software
available under the GNU Version 2 software license.
Bacula is made up of the following five major components or services:
Director, Console, File, Storage, and Monitor services.
(thanks to Aristedes Maniatis for this graphic and the one below)
The Bacula Director service is the program that supervises
all the backup, restore, verify and archive operations. The system
administrator uses the Bacula Director to schedule backups and to
recover files. For more details see the Director Services Daemon Design
Document in the Bacula Developer's Guide. The Director runs as a daemon
(or service) in the background.
The Bacula Console service is the program that allows the
administrator or user to communicate with the Bacula Director
Currently, the Bacula Console is available in three versions:
text-based console interface, QT-based interface, and a
wxWidgets graphical interface.
The first and simplest is to run the Console program in a shell window
(i.e. TTY interface). Most system administrators will find this
completely adequate. The second version is a GNOME GUI interface that
is far from complete, but quite functional as it has most the
capabilities of the shell Console. The third version is a wxWidgets GUI
with an interactive file restore. It also has most of the capabilities
of the shell console, allows command completion with tabulation, and
gives you instant help about the command you are typing. For more
details see the Bacula Console Design Document_ConsoleChapter.
The Bacula File service (also known as the Client program) is the software
program that is installed on the machine to be backed up.
It is specific to the
operating system on which it runs and is responsible for providing the
file attributes and data when requested by the Director. The File
services are also responsible for the file system dependent part of
restoring the file attributes and data during a recovery operation. For
more details see the File Services Daemon Design Document in the Bacula
Developer's Guide. This program runs as a daemon on the machine to be
In addition to Unix/Linux File daemons, there is a Windows File daemon
(normally distributed in binary format). The Windows File daemon runs
on current Windows versions (NT, 2000, XP, 2003, and possibly Me and
The Bacula Storage services consist of the software programs that
perform the storage and recovery of the file attributes and data to the
physical backup media or volumes. In other words, the Storage daemon is
responsible for reading and writing your tapes (or other storage media,
e.g. files). For more details see the Storage Services Daemon Design
Document in the Bacula Developer's Guide. The Storage services runs as
a daemon on the machine that has the backup device (usually a tape
The Catalog services are comprised of the software programs
responsible for maintaining the file indexes and volume databases for
all files backed up. The Catalog services permit the system
administrator or user to quickly locate and restore any desired file.
The Catalog services sets Bacula apart from simple backup programs like
tar and bru, because the catalog maintains a record of all Volumes used,
all Jobs run, and all Files saved, permitting efficient restoration and
Volume management. Bacula currently supports three different databases,
MySQL, PostgreSQL, and SQLite, one of which must be chosen when building
The three SQL databases currently supported (MySQL, PostgreSQL or
SQLite) provide quite a number of features, including rapid indexing,
arbitrary queries, and security. Although the Bacula project plans to support other
major SQL databases, the current Bacula implementation interfaces only
to MySQL, PostgreSQL and SQLite. For the technical and porting details
see the Catalog Services Design Document in the developer's documented.
The packages for MySQL and PostgreSQL are available for several operating
Alternatively, installing from the
source is quite easy, see the Installing and Configuring
MySQLMySqlChapter chapter of this document for the details. For
more information on MySQL, please see:
www.mysql.comhttp://www.mysql.com. Or see the
Installing and Configuring PostgreSQLPostgreSqlChapter chapter of this
document for the details. For more information on PostgreSQL, please
Configuring and building SQLite is even easier. For the details of
configuring SQLite, please see the Installing and Configuring
SQLiteSqlLiteChapter chapter of this document.
A Bacula Monitor service is the program that allows the
administrator or user to watch current status of Bacula Directors,
Bacula File Daemons and Bacula Storage Daemons.
Currently, only a GTK+ version is available, which works with GNOME,
KDE, or any window manager that supports the FreeDesktop.org system tray
To perform a successful save or restore, the following four daemons must be
configured and running: the Director daemon, the File daemon, the Storage
daemon, and the Catalog service (MySQL, PostgreSQL or SQLite).
In order for Bacula to understand your system, what clients you want backed
up and how, you must create a number of configuration files containing
resources (or objects). The following presents an overall picture of this:
Bacula is in a state of evolution, and as a consequence, this manual
will not always agree with the code. If an item in this manual is preceded by
an asterisk (*), it indicates that the particular feature is not implemented.
If it is preceded by a plus sign (+), it indicates that the feature may be
If you are reading this manual as supplied in a released version of the
software, the above paragraph holds true. If you are reading the online
version of the manual,
www.bacula.orghttp://www.bacula.org, please bear in
mind that this version describes the current version in development (in the
CVS) that may contain features not in the released version. Just the same, it
generally lags behind the code a bit.
To get Bacula up and running quickly, the author recommends
that you first scan the
Terminology section below, then quickly review the next chapter entitled
The Current State of BaculaStateChapter, then the
Getting Started with BaculaQuickStartChapter, which will
give you a quick overview of getting Bacula running. After which, you should
proceed to the chapter on
Installing BaculaInstallChapter, then
How to Configure BaculaConfigureChapter, and finally the
The person or persons responsible for administrating the Bacula system.
The term Backup refers to a Bacula Job that saves files.
- Bootstrap File
The bootstrap file is an ASCII file containing a compact form of
commands that allow Bacula or the stand-alone file extraction utility
(bextract) to restore the contents of one or more Volumes, for
example, the current state of a system just backed up. With a bootstrap
file, Bacula can restore your system without a Catalog. You can create
a bootstrap file from a Catalog to extract any file or files you wish.
The Catalog is used to store summary information about the Jobs,
Clients, and Files that were backed up and on what Volume or Volumes.
The information saved in the Catalog permits the administrator or user
to determine what jobs were run, their status as well as the important
characteristics of each file that was backed up, and most importantly,
it permits you to choose what files to restore.
The Catalog is an
online resource, but does not contain the data for the files backed up.
Most of the information stored in the catalog is also stored on the
backup volumes (i.e. tapes). Of course, the tapes will also have a
copy of the file data in addition to the File Attributes (see below).
The catalog feature is one part of Bacula that distinguishes it from
simple backup and archive programs such as dump and tar.
In Bacula's terminology, the word Client refers to the machine being
backed up, and it is synonymous with the File services or File daemon,
and quite often, it is referred to it as the FD. A Client is defined in a
configuration file resource.
The program that interfaces to the Director allowing the user or system
administrator to control Bacula.
Unix terminology for a program that is always present in the background to
carry out a designated task. On Windows systems, as well as some Unix
systems, daemons are called Services.
The term directive is used to refer to a statement or a record within a
Resource in a configuration file that defines one specific setting. For
example, the Name directive defines the name of the Resource.
The main Bacula server daemon that schedules and directs all Bacula
operations. Occasionally, the project refers to the Director as DIR.
A backup that includes all files changed since the last Full save started.
Note, other backup programs may define this differently.
- File Attributes
The File Attributes are all the information necessary about a file to
identify it and all its properties such as size, creation date, modification
date, permissions, etc. Normally, the attributes are handled entirely by
Bacula so that the user never needs to be concerned about them. The
attributes do not include the file's data.
- File Daemon
The daemon running on the client computer to be backed up. This is also
referred to as the File services, and sometimes as the Client services or the
A FileSet is a Resource contained in a configuration file that defines
the files to be backed up. It consists of a list of included files or
directories, a list of excluded files, and how the file is to be stored
(compression, encryption, signatures). For more details, see the
FileSet Resource definitionFileSetResource in the Director
chapter of this document.
A backup that includes all files changed since the last Full, Differential,
or Incremental backup started. It is normally specified on the Level
directive within the Job resource definition, or in a Schedule resource.
A Bacula Job is a configuration resource that defines the work that
Bacula must perform to backup or restore a particular Client. It
consists of the Type (backup, restore, verify, etc), the Level (full, incremental,...), the FileSet, and Storage the
files are to be backed up (Storage device, Media Pool). For more
details, see the Job Resource definitionJobResource in the
Director chapter of this document.
The program that interfaces to all the daemons allowing the user or
system administrator to monitor Bacula status.
A resource is a part of a configuration file that defines a specific
unit of information that is available to Bacula. It consists of several
directives (individual configuration statements). For example, the Job resource defines all the properties of a specific Job: name,
schedule, Volume pool, backup type, backup level, ...
A restore is a configuration resource that describes the operation of
recovering a file from backup media. It is the inverse of a save,
except that in most cases, a restore will normally have a small set of
files to restore, while normally a Save backs up all the files on the
system. Of course, after a disk crash, Bacula can be called upon to do
a full Restore of all files that were on the system.
A Schedule is a configuration resource that defines when the Bacula Job
will be scheduled for execution. To use the Schedule, the Job resource
will refer to the name of the Schedule. For more details, see the
Schedule Resource definitionScheduleResource in the Director
chapter of this document.
This is a program that remains permanently in memory awaiting
instructions. In Unix environments, services are also known as
- Storage Coordinates
The information returned from the Storage Services that uniquely locates
a file on a backup medium. It consists of two parts: one part pertains
to each file saved, and the other part pertains to the whole Job.
Normally, this information is saved in the Catalog so that the user
doesn't need specific knowledge of the Storage Coordinates. The Storage
Coordinates include the File Attributes (see above) plus the unique
location of the information on the backup Volume.
- Storage Daemon
The Storage daemon, sometimes referred to as the SD, is the code that
writes the attributes and data to a storage Volume (usually a tape or
Normally refers to the internal conversation between the File daemon and
the Storage daemon. The File daemon opens a session with the
Storage daemon to save a FileSet or to restore it. A session has a
one-to-one correspondence to a Bacula Job (see above).
A verify is a job that compares the current file attributes to the
attributes that have previously been stored in the Bacula Catalog. This
feature can be used for detecting changes to critical system files
similar to what a file integrity checker like Tripwire does.
One of the major advantages of
using Bacula to do this is that on the machine you want protected such
as a server, you can run just the File daemon, and the Director, Storage
daemon, and Catalog reside on a different machine. As a consequence, if
your server is ever compromised, it is unlikely that your verification
database will be tampered with.
Verify can also be used to check that the most recent Job data written
to a Volume agrees with what is stored in the Catalog (i.e. it compares
the file attributes), *or it can check the Volume contents against the
original files on disk.
An Archive operation is done after a Save, and it consists of removing the
Volumes on which data is saved from active use. These Volumes are marked as
Archived, and may no longer be used to save files. All the files contained
on an Archived Volume are removed from the Catalog. NOT YET IMPLEMENTED.
- Retention Period
There are various kinds of retention periods that Bacula recognizes.
The most important are the File Retention Period, Job
Retention Period, and the Volume Retention Period. Each of these
retention periods applies to the time that specific records will be kept
in the Catalog database. This should not be confused with the time that
the data saved to a Volume is valid.
The File Retention Period determines the time that File records are kept
in the catalog database. This period is important for two reasons: the
first is that as long as File records remain in the database, you
can "browse" the database with a console program and restore any
individual file. Once the File records are removed or pruned from the
database, the individual files of a backup job can no longer be
"browsed". The second reason for carefully choosing the File Retention
Period is because the volume of
the database File records use the most storage space in the
database. As a consequence, you must ensure that regular "pruning" of
the database file records is done to keep your database from growing
too large. (See the Console prune
command for more details on this subject).
The Job Retention Period is the length of time that Job records will be
kept in the database. Note, all the File records are tied to the Job
that saved those files. The File records can be purged leaving the Job
records. In this case, information will be available about the jobs
that ran, but not the details of the files that were backed up.
Normally, when a Job record is purged, all its File records will also be
The Volume Retention Period is the minimum of time that a Volume will be
kept before it is reused. Bacula will normally never overwrite a Volume
that contains the only backup copy of a file. Under ideal conditions,
the Catalog would retain entries for all files backed up for all current
Volumes. Once a Volume is overwritten, the files that were backed up on
that Volume are automatically removed from the Catalog. However, if
there is a very large pool of Volumes or a Volume is never overwritten,
the Catalog database may become enormous. To keep the Catalog to a
manageable size, the backup information should be removed from the
Catalog after the defined File Retention Period. Bacula provides the
mechanisms for the catalog to be automatically pruned according to the
retention periods defined.
A Scan operation causes the contents of a Volume or a series of Volumes
to be scanned. These Volumes with the information on which files they
contain are restored to the Bacula Catalog. Once the information is
restored to the Catalog, the files contained on those Volumes may be
easily restored. This function is particularly useful if certain
Volumes or Jobs have exceeded their retention period and have been
pruned or purged from the Catalog. Scanning data from Volumes into the
Catalog is done by using the bscan program. See the bscan
sectionbscan of the Bacula Utilities Chapter of this manual for more
A Volume is an archive unit, normally a tape or a named disk file where
Bacula stores the data from one or more backup jobs. All Bacula Volumes
have a software label written to the Volume by Bacula so that it
identifies what Volume it is really reading. (Normally there should be
no confusion with disk files, but with tapes, it is easy to mount the
Bacula is a backup, restore and verification program and is not a
complete disaster recovery system in itself, but it can be a key part of one
if you plan carefully and follow the instructions included in the
Disaster RecoveryRescueChapter Chapter of this manual.
With proper planning, as mentioned in the Disaster Recovery chapter,
Bacula can be a central component of your disaster recovery system. For
example, if you have created an emergency boot disk, and/or a Bacula Rescue disk to
save the current partitioning information of your hard disk, and maintain a
complete Bacula backup, it is possible to completely recover your system from
"bare metal" that is starting from an empty disk.
If you have used the WriteBootstrap record in your job or some other
means to save a valid bootstrap file, you will be able to use it to extract
the necessary files (without using the catalog or manually searching for the
files to restore).
The following block diagram shows the typical interactions between the Bacula
Services for a backup job. Each block represents in general a separate process
(normally a daemon). In general, the Director oversees the flow of
information. It also maintains the Catalog.