a computer should only be part of one domain

client/templates/hosts.j2

 127.0.0.1	localhost
-127.0.1.1	{{ inventory_hostname }}.{{ domain[0] }}	{{ inventory_hostname }}
+127.0.1.1	{{ inventory_hostname }}.{{ domain }}	{{ inventory_hostname }}
 
 # The following lines are desirable for IPv6 capable hosts
 ::1     localhost ip6-localhost ip6-loopback