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NTP: Creating an NTP Server
Introduction
The NTP server is a time server. It provides time based on atomic clock references.
Installation
Debian
Super quick:
apt-get install ntp
Solaris
On Solaris, NTP is normally installed by default. Otherwise, search for packages containing ntpd. You will need to copy the server configuration file:
cp /etc/inet/ntp.server /etc/inet/ntp.conf
Configuration
Here is some information before diving into configuration files:
- stratum: indicates that it’s not very reliable data
- 127.127.1.0: time given by the machine (BIOS)
- peer: defines a server of the same stratum as the server (same level/same geographic location), which allows for more reliability. Using 1 server + peers provides a more refined configuration than having only geographically distant servers.
Debian
Here’s the configuration file for a time server (/etc/inet/ntp.conf):
# /etc/ntp.conf, configuration for ntpd
# ntpd will use syslog() if logfile is not defined
logfile /var/log/ntpd
driftfile /var/lib/ntp/ntp.drift
statsdir /var/log/ntpstats/
statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable
# Servers to use to update
server 0.fr.pool.ntp.org prefer
server 1.fr.pool.ntp.org
server 2.fr.pool.ntp.org
# ... and use the local system clock as a reference if all else fails
server 127.127.1.0
# fudge 127.127.1.0 stratum 13
# Local users may interrogate the ntp server more closely.
restrict 127.0.0.1
# Allow local network to synchronize to this server
restrict 192.168.0.0 mask 255.255.255.0 nomodify notrap
broadcastdelay 0.008
After configuring and restarting the service, you must wait a few minutes for the server to synchronize.
Solaris
Here’s the configuration file for Solaris (/etc/inet/ntp.conf):
#
# Copyright 1996-2003 Sun Microsystems, Inc. All rights reserved.
# Use is subject to license terms.
#
# /etc/inet/ntp.server
#
# An example file that could be copied over to /etc/inet/ntp.conf and
# edited; it provides a configuration template for a server that
# listens to an external hardware clock, synchronizes the local clock,
# and announces itself on the NTP multicast net.
#
# This is the external clock device. The following devices are
# recognized by xntpd 3-5.93e:
#
# XType Device RefID Description
# -------------------------------------------------------
# 1 local LCL Undisciplined Local Clock
# 2 trak GPS TRAK 8820 GPS Receiver
# 3 pst WWV PSTI/Traconex WWV/WWVH Receiver
# 4 wwvb WWVB Spectracom WWVB Receiver
# 5 true TRUE TrueTime GPS/GOES Receivers
# 6 irig IRIG IRIG Audio Decoder
# 7 chu CHU Scratchbuilt CHU Receiver
# 8 parse ---- Generic Reference Clock Driver
# 9 mx4200 GPS Magnavox MX4200 GPS Receiver
# 10 as2201 GPS Austron 2201A GPS Receiver
# 11 arbiter GPS Arbiter 1088A/B GPS Receiver
# 12 tpro IRIG KSI/Odetics TPRO/S IRIG Interface
# 13 leitch ATOM Leitch CSD 5300 Master Clock Controller
# 15 * * TrueTime GPS/TM-TMD Receiver
# 17 datum DATM Datum Precision Time System
# 18 acts ACTS NIST Automated Computer Time Service
# 19 heath WWV Heath WWV/WWVH Receiver
# 20 nmea GPS Generic NMEA GPS Receiver
# 22 atom PPS PPS Clock Discipline
# 23 ptb TPTB PTB Automated Computer Time Service
# 24 usno USNO USNO Modem Time Service
# 25 * * TrueTime generic receivers
# 26 hpgps GPS Hewlett Packard 58503A GPS Receiver
# 27 arc MSFa Arcron MSF Receiver
#
# * All TrueTime receivers are now supported by one driver, type 5.
# Types 15 and 25 will be retained only for a limited time and may
# be reassigned in future.
#
# Some of the devices benefit from "fudge" factors. See the xntpd
# documentation.
# Either a peer or server. Replace "XType" with a value from the
# table above.
# Servers to use to update
server 0.fr.pool.ntp.org prefer
server 1.fr.pool.ntp.org
server 2.fr.pool.ntp.org
# fudge 127.127.XType.0 stratum 0
broadcast 224.0.1.1 ttl 4
enable auth monitor
driftfile /var/ntp/ntp.drift
statsdir /var/ntp/ntpstats/
filegen peerstats file peerstats type day enable
filegen loopstats file loopstats type day enable
filegen clockstats file clockstats type day enable
keys /etc/inet/ntp.keys
trustedkey 0
requestkey 0
controlkey 0
Create a drift file as indicated in the configuration:
touch /etc/inet/ntp.drift
Then enable the service:
svcadm enable svc:/network/ntp:default
NTP Clients
Linux
To synchronize a Unix/Linux machine, use this command:
ntpdate my_time_server
Solaris
It’s quite simple on Solaris:
cp /etc/inet/ntp.client /etc/inet/ntp.conf
svcadm enable svc:/network/ntp:default
Windows
From a Windows machine:
net time /setsntp:my_time_server
net time /querysntp
net stop w32time && net start w32time
FAQ
How to change the timezone?
On Debian, there’s the tzconfig command! It’s very practical:
tzconfig
If this doesn’t work, try:
dpkg-reconfigure tzdata
“no server suitable for synchronization found”
If you encounter this error, there could be two reasons:
- Your NTP server needs to synchronize before it can provide time to other servers. This can sometimes take some time (~30 min).
- One of the servers in your list is unreachable, which makes your server unavailable for updates. Comment it out temporarily.
Once the following line appears in the logs (“clock is now synced”), everything is OK:
May 24 16:48:05 chronos ntpd[14262]: ntp engine ready
May 24 16:48:24 chronos ntpd[14262]: peer 91.121.45.45 now valid
May 24 16:48:24 chronos ntpd[14262]: peer 81.93.183.116 now valid
May 24 16:48:27 chronos ntpd[14262]: peer 94.23.220.143 now valid
May 24 17:27:13 chronos ntpd[14262]: clock is now synced
Last updated 06 Oct 2011, 11:10 CEST.