gbak(1) Backup and restore Firebird databases


gbak -b [backup option...] source target

gbak -c [restore option...] source target

gbak -r [restore option...] source target


gbak is the tool for managing Firebird database backup and restore.

In backup mode source is an existing database path (may include server name) and target is backup file name. It could be also a special name like "stdout" (to redirect backup data to the standard output) or /dev/st to put the backup on tape.

In restore mode source is existing backup file (or special name like "stdin" for the standard input or /dev/st to get the backup from tape, etc.) and target is path to firebird database and may include server name.

All options can be abbreviated. Below both full versions of options and the shortest possible versions are given.


-user username
User name to use when connecting to database. Overrides the setting in the "ISC_USER" environment variable.
-ro[le] role_name
SQL role to use when connecting to database. Overrides the "ISC_ROLE" environment variable.
-pas[sword] password
Password to use when connecting to database. Overrides the "ISC_PASSWORD" environment variable.
Use the services manager when talking to a database.
-st[atistics] T|D|R|W
Show some statistics. Each flag enables a function:
Time from start
Delta time
Page reads
Page writes
Report each action.

Displays verbose information about what metadata is being processed, what table is being backed up/restored and how many records are processed.

-y path
Redirect status/error messages to the given path.
-z Report full version number before doing anything else.


Turn on backup mode
Convert external tables into ordinary (internal) tables. Normally external tables are ignored during backup and restore. With the -convert option external tables are included in the backup as any other regular table. When such a backup is restored, these previously external tables are created as regular tables.
-fa[ctor] num
Blocking factor. Output is written in blocks of num bytes. Useful when backing up to a tape.
Inhibit garbage collection.

Normally Firebird runs a garbage collector when reading through the tables. Since the backup process reads all the tables, this forces garbage collection of the whole database. In case you make the backup just to restore it over the existing database this garbage collection is unnecessary. Another reason to use this options is if a garbage collection is engaged by other means - either by using gfix or the automatic sweep. Using this switch speeds up the backup process and also can help in some cases of backing up damaged databases.

Ignore records with bad checksums.

This option should be used only when backing up damaged databases.

Ignore transactions in limbo.

This switch causes the backup process to ignore transactions in limbo state.

Backup metadata only.

With this option only the metadata is written to the backup. This includes all tables/views/triggers/indexes/stored procedures/domains/generators etc. No table data is included in the backup. Such a backup is useful for creating an ``empty'' copy of the database.

Use non-transportable backup format.

By default a ``transportable'' backup format is used. This means you can backup a database on little-endian machine and restore it on big-endian machine and vice versa. By using the -nt option the backup is only useful on machines with the same ``endianness''.

Ssave old-style metadata descriptions.


Turn on restore mode.

The target database will be created and must not already exist.

Like the -create_database option, but the target is overwritten if it exists.
-r[ecreate_database] o[verwrite]]
Like the -create_database option, but by adding "overwrite" one can force replacement of the target database.
-bu[ffers] num
When creating target database, ignore information about database buffers stored in the backup and use specified number of buffers.
Normally, Firebird uses RLE compression for strings when storing them on disk. This option turns this compression off.
Restore indexes in inactive state. This can be used to restore a backup, containing data inconsistent with foreign key/unique constraints.
Do not create shadows when restoring.

Normally and database shadows are created during restore. This option inhibits this.

-mo[de] access
Restore database with given access mode.

Valid values for access are "read_only" and "read_write". Default is to restore the database with its original access mode.

Restore database without its validity constraints. This includes foreign key, unique and check constraints. Useful for restoring a backup, containing inconsistent data.
Commit restoring transaction after each table.
-p[age_size] num
Override page size stored in the backup. Valid values for num are 1024, 2048, 4096, 8192, 16384 and 32768.
Normally, Fireburd reserves some space on each data page for further use. This reserved space is used for newly inserted data and for keeping older versions of the data. Having space reserved for this purpose ``near'' to the data speeds up modifications. If the database will used mainly for read operations, specifying use_all_space will save some space.

This option is particularly useful when restoring a read-only database, since read-only databases do not need any additional space for back-versions.

-fix_fss_metadata charset

When restoring metadata, in case it is not valid UTF8, try to convert from the specified character set. Useful when table descriptions are given in some national non-UTF8 encoding, which was possible with Firebird before version 2.5.

-fix_fss_data charset
When restoring table data, in case a column defined with UNICODE_FSS character set contains no valid UTF8 (which was possible with versions of Firebird prior to 2.5), try to convert the data from the specified character set.


Previously, Firebird was not able to work with 64-bit file pointers thus limiting databases to (about) 2GB of size per database.

Since 2GB is not much of data since years, there is a mechanism for spreading the database into multiple files. This way you can have multiple 2GB files, containing all the data.

When restoring to multiple-file database the target argument is of form: file_1 pages_1 file_2 pages_2 ... file_N-1 pages_N-1 file_N

Each pages_n argument specifies at most how many pages to put in file_n. Last in the list is a filename without page limit - it will contain all the pages that don't fit in file_N-1. Note that pages_n is measured in pages, not bytes, so the maximum possible number depends on page size.

Imagine you have a filesystem (or an ancient OS) which only supports 32-bit file pointers. To play safe, you decide to split your database on 2GB files. If the page size for the database is 8192, then each file can have up to 2*1024*1024*1024/8192 = 262144 pages.

NOTE: On a recent OS and filesystem Firebird can use 64-bit file pointers rendering multi-file databases unnecessary.


As all other Firebird utilities, gbak accepts the following environment variables:
Default value for the -user option.
Default value for the -role option.
Default value for the -password option.


In all examples the -user, -role and -password options are omitted for clarity. In a real world situation they (or their corresponding enviromnemt variables) should be used.

Note that filename extensions used here are just recommended. Using unified extensions scheme helps guess file type just by looking at its extension but is not mandatory.

Here are some commonly used extensions:

Firebird database
Firebird database, legacy extension from the days when Firebird was Interbase. "gdb" actually comes from Grotton database, named after the company that created the software back in 1984.
Second file of multi-file database.
N-th file of multi-file database.
Firebird backup file.
Legacy extension for backup file.
Gzipped backup file.

Backup a database into a compressed format

 gbak -b db-srv:/database.fdb stdout | gzip > /file.fbk.gz

Restore a compressed backup into a new filename

 zcat /file.fbk.gz | gbak -c stdin db-srv:/new-database.fdb


Copyright (c) 2004,2007 Damyan Ivanov <[email protected]>.

Permission is granted to use this document, with or without modifications, provided that this notice is retained. If we meet some day, and you think this stuff is worth it, you can buy me a beer in return.