Introduction to NTP

The NTP package contains a client and server to keep the time synchronized between various computers over a network. This package is the official reference implementation of the NTP protocol.

Package information

NTP dependencies

Installation of NTP

Install NTP by running the following commands:

./configure --prefix=/usr --bindir=/usr/sbin \
    --sysconfdir=/etc &&
make &&
make install

Configuring NTP

Config files


Configuration Information

The following configuration file defines various NTP stratum 2 servers with open access from different continents. It also creates a drift file where ntpd stores the frequency offset. Since the documentation included with the package is sparse, visit the NTP website at http://www.ntp.org/ for more information.

cat > /etc/ntp.conf << "EOF"
# Africa
server tock.nml.csir.co.za

# Asia
server ntp.shim.org

# Australia
server ntp.saard.net
# Europe
server ntp.tuxfamily.net

# North America
server clock.psu.edu

driftfile /var/cache/ntp.drift

Synchronizing the time

There are two options. Option one is to run ntpd continuously and allow it to synchronize the time in a gradual manner. The other option is to run ntpd periodically (using cron) and update the time each time ntpd is scheduled.

If you choose Option one, then install the /etc/rc.d/init.d/ntp init script included in the blfs-bootscripts-5.1 package.

make install-ntp

If you prefer to run ntpd periodically, add the following command to root's crontab:

ntpd -q


The NTP package contains ntp-wait, ntptrace, ntpd, ntpdate, ntpdc, ntpq, ntptime, tickadj and ntp-keygen.



ntp-wait is useful at boot time, to delay the boot sequence until ntpd has set the time.


ntptrace traces a chain of NTP servers back to the primary source.


ntpd is a NTP daemon that runs in the background and keeps the date and time synchronized based on response from configured NTP servers. It also functions as a NTP server.


ntpdate is a client program that sets the date and time based on the response from an NTP server. This command is deprecated.


ntpdc is used to query the NTP daemon about its current state and to request changes in that state.


ntpq is an utility program used to monitor ntpd operations and determine performance.


ntptime reads and displays time-related kernel variables.


tickadj reads, and optionally modifies, several timekeeping-related variables in older kernels that do not have support for precision timekeeping.


ntp-keygen generates cryptographic data files used by the NTPv4 authentication and identification schemes.