Fluent Bit might optionally use a configuration file to define how the service will behave, and before proceeding we need to understand how the configuration schema works.
The schema is defined by three concepts:
Indented Configuration Mode
A simple example of a configuration file is as follows:
[SERVICE]# This is a commented lineDaemon offlog_level debug
A section is defined by a name or title inside brackets. Looking at the example above, a Service section has been set using [SERVICE] definition. Section rules:
All section content must be indented (4 spaces ideally).
Multiple sections can exist on the same file.
A section is expected to have comments and entries, it cannot be empty.
Any commented line under a section, must be indented too.
A section may contain Entries, an entry is defined by a line of text that contains a Key and a Value, using the above example, the
[SERVICE] section contains two entries, one is the key Daemon with value off and the other is the key Log_Level with the value debug. Entries rules:
An entry is defined by a key and a value.
A key must be indented.
A key must contain a value which ends in the breakline.
Multiple keys with the same name can exist.
Also commented lines are set prefixing the # character, those lines are not processed but they must be indented too.
Fluent Bit configuration files are based in a strict Indented Mode, that means that each configuration file must follow the same pattern of alignment from left to right when writing text. By default an indentation level of four spaces from left to right is suggested. Example:
[FIRST_SECTION]# This is a commented lineKey1 some valueKey2 another value# more comments[SECOND_SECTION]KeyN 3.14
As you can see there are two sections with multiple entries and comments, note also that empty lines are allowed and they do not need to be indented.