Add and apply systemd detector function

fw.py

@@ -5,7 +5,7 @@ import json
 import logging
 
 from utils import (ns_exec, sudo, ADDRESSES, get_network_type,
-                   dhcp_no_free_re, dhcp_ack_re)
+                   dhcp_no_free_re, dhcp_ack_re, is_there_systemd)
 
 DHCP_LOGFILE = getenv('DHCP_LOGFILE', '/var/log/syslog')
 VLAN_CONF = getenv('VLAN_CONF', 'vlan.conf')
@@ -77,8 +77,8 @@ def reload_firewall_vlan(data, save_config=True):
 def reload_dhcp(data):
     with open('/etc/dhcp/dhcpd.conf.generated', 'w') as f:
         f.write("\n".join(data) + "\n")
-    import platform
-    if platform.dist()[0]=="centos":
+    
+    if is_there_systemd():
         sudo(('/bin/systemctl', 'restart','dhcpd'))
     else:
         sudo(('/etc/init.d/isc-dhcp-server', 'restart'))

utils.py

+import os
 from os import getenv
 import subprocess as sp
 import logging
@@ -60,3 +61,17 @@ def ns_exec(args, stdin=None):
     else:
         return sudo(('/sbin/ip', 'netns', 'exec',
                     NETNS) + args, stdin)
+
+
+def is_there_systemd():
+
+    devnull=open(os.devnull,"w")
+
+    try:
+        sp.call(["/bin/systemctl","--version"],stdout=devnull,stderr=devnull)
+    except OSError:
+        devnull.close()
+        return False
+    devnull.close()
+    return True
+