## Configure a system to use NTP ##

[Author](authors.html): Grzegorz Czapli&#324;ski gregory at systemics dot pl FreeBSD

[Reviewer](technical_reviewers.html): Cezary Morga cm@therek.net FreeBSD

[Reviewer](technical_reviewers.html): _name_ _[[contact]]_ _[[BSD_flavour]]_

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### Concept ###

Be familiar with the concepts in RFC 868,
the importance of synchronizing time(((time, network))) 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). OpenBSD uses /etc/ntpd.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)


