YAML Tips and Gotchas

The configuration file uses YAML for its syntax. When you edit the file to modify configuration settings, there are a few things that you should know.

Indentation is meaningful in YAML. Make sure that you use spaces, rather than tab characters, to indent sections.

In the default configuration files and in all the examples in the documentation, we use 2 spaces per indentation level. We recommend you do the same.

The best way to understand where to define a configuration option is by looking at the provided sample configuration files. The configuration files contain most of the default configurations that are available for the Beat. To change a setting, simply uncomment the line and change the values.

You can test your configuration file to verify that the structure is valid. Simply change to the directory where the binary is installed, and run the Beat in the foreground with the -configtest flag specified. For example:

packetbeat -c packetbeat.yml -configtest

You’ll see a message if the Beat finds an error in the file.

If you need to specify a regular expression in a YAML file, it’s a good idea to wrap the regular expression in single quotation marks to work around YAML’s tricky rules for string escaping.

For more information about YAML, see http://yaml.org/.

Windows paths in particular sometimes contain spaces or characters, such as drive letters or triple dots, that may be misinterpreted by the YAML parser.

To avoid this problem, it’s a good idea to wrap paths in single quotation marks.

If you use a leading zero (for example, 09) in a numeric field without wrapping the value in single quotation marks, the value may be interpreted incorrectly by the YAML parser. If the value is a valid octal, it’s converted to an integer. If not, it’s converted to a float.

To prevent unwanted type conversions, avoid using leading zeros in field values, or wrap the values in single quotation marks.