Index: etc/icinga2/conf.d/groups.conf
--- etc/icinga2/conf.d/groups.conf.orig
+++ etc/icinga2/conf.d/groups.conf
@@ -2,6 +2,12 @@
  * Host group examples.
  */
 
+object HostGroup "openbsd-servers" {
+  display_name = "OpenBSD Servers"
+
+  assign where host.vars.os == "OpenBSD"
+}
+
 object HostGroup "linux-servers" {
   display_name = "Linux Servers"
 
