Add NTP to the router/gateway

This post is obsolete and has been superseded

NTP is useful to set the time of LAN devices. In addition, the 'adjtimex' package updates the hardware clock. (Slightly out-of-date instructions)

1. Install NTP with the following command:
   

   apt-get install ntp adjtimex

2. Edit the /etc/ntp.conf file to broadcast time to the LAN:
   

   ## Around Line 48
   # If you want to provide time to your local subnet, change the next line.
   # (Again, the address is an example only.)
   #broadcast 192.168.123.255
   broadcast 192.168.1.0

3. Edit /etc/hosts.allow and /etc/hosts.deny to limit access to ntpd. Edit /etc/hosts.allow to look more like this:
   

   sshd:              192.168.1.0/26
   debtorrent-client: 192.168.1.0/26
   ntpd:              192.168.1.0/26
   ALL:               192.168.1.0/26
   # /26 creates the range .1.0 - .1.62
   

   And edit /etc/hosts.deny to look more like this:
   

   sshd:              ALL
   debtorrent-client: ALL
   ntpd:              ALL
   ALL:               ALL
   

4. xinted and dnsmasq do not interact with ntpd, and no changes are required.
5. Firewall rules to open those two listening ports. Edit the file /etc/network/if-up.d/00-firewall to add the following rules:
   

   # ALLOW INCOMING OPEN PORTS TO THE SERVER FROM OUTSIDE HERE
   #
   # Allow incoming debtorrent requests on TCP ports 9899-9990
   iptables -A INPUT -p tcp --dport 9899 -j ACCEPT
   iptables -A INPUT -p tcp --dport 9900 -j ACCEPT
   #
   # Allow NTP syncs on UDP port 123
   iptables -A INPUT -p udp --dport 123 -j ACCEPT 
   iptables -A OUTPUT -p udp --sport 123 -j ACCEPT
   #
   #
   

6. Restart ntpd with these commands:
   

   sh /etc/network/if-up.d/00-firewall  # Reload the firewall
   service ntpd restart                 # Reload /etc/ntp.conf