The hierarchy
So far, we've only used a single Hiera data source (common.yaml). Actually, you can have as many data sources as you like. Each usually corresponds to a YAML file, and they are listed in the hierarchy section of the hiera.yaml file, in priority order:
hierarchy:
- name: "Common defaults"
path: "common.yaml"
- name: "Source 1"
path: "source1.yaml"
- name: "Source 2"
path: "source2.yaml"
- name: "Source 3"
path: "source3.yaml"It can be helpful to organize Hiera data into separate files; for example, all the configuration relating to web hosts could be stored in a webhost.yaml file. In general, though, you should keep as much data as possible in the common file, simply because it's easier to find and maintain data if it's in one place rather than scattered throughout several files.
Dealing with multiple values
You may be wondering what happens if the same key is listed in more than one Hiera data source. For example, imagine source1.yaml contains the following...
