Network Time Protocol Services

Applicable to: FreeBSD 4.x
Updated: January 1, 2001

This Sheet describes the procedure to set-up time services to keep the FreeBSD machine synchronized with NIST's stratum-1 clock in Boulder, Colorado, and to act as a time server for other computers on the local network. For some interesting information on time, please read the NIST's Time and Frequency FAQ and the article Computer Time Synchronization (PDF document).

1. Edit /etc/rc.conf:

   ### Network Time Services options: ###
   xntpd_enable="YES"
   xntpd_program="ntpd"
   xntpd_flags="-p /var/run/ntpd.pid"

2. Create /etc/ntp.conf:

   server time.nist.gov prefer
   server 127.127.1.0
   fudge 127.127.1.0 stratum 10
   driftfile /etc/ntp.drift

3. Reboot the computer, or start the daemon manually:

   # ntpd -p /var/run/ntpd.pid

4. If your are using ppp(8) for dial-up access to the Internet, edit /etc/ppp/ppp.conf to filter dial-out and keep-alive packets:

   demand:
     ...
    set filter alive 0 deny udp src eq 123
    set filter alive 1 deny udp dst eq 123
    set filter alive 2 permit 0 0
    set filter dial 0 deny udp src eq 123
    set filter dial 1 deny udp dst eq 123
    set filter dial 2 permit 0 0
     ...

   Note: You must restart ppp before these rules take effect.