Configuration Schema

Fluent Bit may use optionally a configuration file to define how the service will behave, and before to proceed we need to understand how the configuration schema works. The schema is defined by three concepts:

A simple example of a configuration file is as follows:

# This is a commented line
Daemon off
log_level debug


A section is defined by a name or title inside brackets. Looking at the example above a Server section has been set using [SERVICE] definition. Section rules:

  • All section content must be indented (4 spaces ideally).

  • Multiples sections can exists on the same file.

  • Under a section is expected to have comments and entries, a section cannot be empty.

  • Any commented line under a section, must be indented too.

Entries: Key/Value

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 the key Log_Level with the value on. 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 exists.

Also commented lines are set prefixing the # character, those lines are not processed but they must be indented too.

Indented Configuration Mode

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 is suggested an indentation level of four spaces from left to right. Example:

# This is a commented line
Key1 some value
Key2 another value
# more comments
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.