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This is the BSDA Study Guide Book written via a wiki collaboration. This is a work in progress. You may contribute to or discuss this specific page at http://bsdwiki.reedmedia.net/wiki/Configure_a_system_to_use_NTP.html. Configure a system to use NTP Concept Be familiar with the concepts in RFC 868, the importance of synchronizing time on server systems and which services in particular are time sensitive. Be able to configure NTP and manually synchronize with a time server as required. Introduction TODO: following are some contributed notes. Some can be removed as refer to too advanced. Also may be FreeBSD-specific. ntpd: Network time protocol (NTP) daemon ntp.conf: NTP daemon configuration file (/etc/ntp.conf) ntpdc: special NTP query program ntpq: standard NTP query program ntpdate: set the date and time via NTP files: /etc/ntp.conf default name of the configuration file /etc/ntp.drift default name of the drift file /etc/ntp.keys default name of the key file /usr/local/etc/ntp.keys private md5 keys /ntpkey RSA private key /ntpkey_host RSA public key ntp_dh Diffie-Hellman agreement parameters which services are time sensitive: configuring NTP: /etc/ntp.conf: server ntp-1.cso.uiuc.edu iburst prefer server ntp1.cs.wisc.edu iburst server neptune.sg.depaul.edu iburst (TODO: use generic example host names or use pool.) driftfile /var/db/ntp.drift restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap To start ntpd the first time without rebooting: ntpd -p /var/run/ntpd.pid After already started: /etc/rc.d/ntpd [start | stop | restart | etc...] Manually synchronize NTP: ntpd -q TODO: be sure to document for different implementations Examples Practice Exercises More information ntpd(8), ntp.conf(5) or ntpd.conf(5), rc.conf(5), rdate(8)