dns/master: Let serial number configured by dnssec-signzone

roles/dns/master/defaults/main.yml

@@ -18,7 +18,6 @@ dnssec_key_length: "4096"
 
 main_nameserver_domain: "ns1.{{ domain }}."
 responsible_mail_name: "admin.{{ domain }}."
-serial_number: "{{ lookup('pipe', 'date +\"%Y%m%d%H\"') }}"
 refresh: 86400
 retry: 7200
 expire: 3600000

roles/dns/master/templates/zone.db

@@ -1,6 +1,6 @@
 $TTL 86400
 @ IN SOA {{ main_nameserver_domain }} {{ responsible_mail_name }} (
-  {{ serial_number }}
+  0
   {{ refresh }}
   {{ retry }}
   {{ expire }}

roles/dns/master/templates/zone.makefile

@@ -16,7 +16,7 @@ ${signed_file}: ${db_file}
 	dnssec-signzone \
 		-3 $$(head -c 1000 /dev/urandom | sha1sum | cut -b 1-16) \
 		-a \
-		-N KEEP \
+		-N unixtime \
 		-o {{ domain | quote }} \
 		-f "$@" \
 		"$<"