public Set<String> os_list(){
      Set<String> r= new HashSet<>();
      for ( String family : osMap.keySet()) {
        JsonOsFamilyEntry fam = osMap.get(family);
        for (String version: fam.getVersions()){
          Set<String> data= new HashSet<>();
          for (String item: fam.getDistro()) {
            data.add(item + version);
          }
          r.addAll(data);
        }
      }
      return r;
    }
Form list of all supported os types
@return one dimension list with os types
ambari-server/src/main/java/org/apache/ambari/server/state/stack/OsFamily.java