If you do not specify a mode switch such as -⁠b[ackup] or -⁠c[reate] etc, then gbak will perform a backup as if the -⁠b[ackup] switch had been specified — provided that the other switches specified are correct for a backup.

Only a SYSDBA, a user with the RDB$ADMIN role, the owner of a database, or a user with the USE_GBAK_UTILITY system privilege can take a backup of the database.However, any authenticated user can restore a database backup using the -⁠c[reate] switch (in Firebird 3.0 and higher, this user will need the CREATE DATABASE DDL privilege).This means that you must make sure you prevent your backup files from falling into the wrong hands because there is nothing then to stop unauthorised people from seeing your data by the simple process of restoring your backups onto their server.

The database restore will fail, of course, if the user carrying it out is not the database owner and a database with the same filename already exists.

The -⁠y suppress_output switch is supposed to cause all output to be suppressed.Similar in fact to running with -⁠v[erify] not specified.However, all it seems to do is cause the output (according to the -⁠v[erify] switch setting) to be written to a file called suppress_output, however this only works once because the next run of gbak with -⁠y suppress_output will fail because the file, suppress_output, already exists.

It is possible that this problem was introduced at version 2 for Firebird, because both 2.0 and 2.1 versions actually use the -⁠y suppress switch rather then -⁠y suppress_output.Using this (shorter) option does work as intended and the output is indeed suppressed.

If you specify a log filename with the -⁠y <log file> switch, and the file already exists, then even though the firebird user owns the file, and has write permissions to it, gbak cannot overwrite it.You must always specify the name of a log file that doesn’t exist.On Linux systems, the following might help:

The above is quite useful in as much as it prevents you from overwriting previous backups that may be required.The downside is that you now need to introduce a housekeeping system to tidy away old, unwanted backups to prevent your backup area filling up.

Gbak recognizes the literal strings stdin and stdout as source or destination filenames.In POSIX systems, when the standard input and/or standard output channels are used, it is not permitted to execute seek operations on these channels.Using stdin or stdout as filenames with gbak will force gbak to use processing that will not seek on the input or output channels, making them suitable for use in pipes — as per the examples in the recipes section above.

These filenames, while they appear to be POSIX names, are definitely not synonyms for /dev/stdin or /dev/stdout, they are simply literals that gbak checks for while processing its parameters.Do not attempt to use names /dev/stdin or /dev/stdout in a piped process as it will most likely fail.

If you wish to create a backup file actually named either stdin or stdout, then you should specify the filename as a full, or relative, path name such as ./stdin or ./stdout, which causes gbak to treat them as a literal filename rather than a special filename that causes different to normal processing during the backup or restore process.