ntp-4.2.8p1
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.
This package is known to build and work properly using an LFS-7.7
platform.
Package Information
ntp Dependencies
Optional
libcap-2.24 with PAM, OpenSSL-1.0.2, and libedit
User Notes: http://wiki.linuxfromscratch.org/blfs/wiki/ntp
Installation of ntp
There should be a dedicated user and group to take control of the
ntpd daemon after it
is started. Issue the following commands as the root user:
groupadd -g 87 ntp &&
useradd -c "Network Time Protocol" -d /var/lib/ntp -u 87 \
-g ntp -s /bin/false ntp
Install ntp by running the
following commands:
./configure --prefix=/usr \
--bindir=/usr/sbin \
--sysconfdir=/etc \
--enable-linuxcaps \
--with-lineeditlibs=readline \
--docdir=/usr/share/doc/ntp-4.2.8p1 &&
make
To test the results, issue: make
check.
Now, as the root user:
make install &&
install -v -o ntp -g ntp -d /var/lib/ntp
Command Explanations
--bindir=/usr/sbin: This
parameter places the administrative programs in /usr/sbin.
--enable-linuxcaps: ntpd is
run as user ntp, so use Linux capabilities for non-root clock
control.
--with-lineeditlibs=readline: This
option enables Readline support
for ntpdc and
ntpq programs. If
omitted, libedit will be used if
installed, otherwise no readline capabilites will be compiled.
Configuring ntp
Config Files
/etc/ntp.conf
Configuration Information
The following configuration file defines various ntp servers with
open access from different continents. It also creates a drift
file where ntpd
stores the frequency offset and a pid file to store the
ntpd process ID.
Since the documentation included with the package is sparse,
visit the ntp website at http://www.ntp.org/ and http://www.pool.ntp.org/ for more
information.
cat > /etc/ntp.conf << "EOF"
# Asia
server 0.asia.pool.ntp.org
# Australia
server 0.oceania.pool.ntp.org
# Europe
server 0.europe.pool.ntp.org
# North America
server 0.north-america.pool.ntp.org
# South America
server 2.south-america.pool.ntp.org
driftfile /var/lib/ntp/ntp.drift
pidfile /var/run/ntpd.pid
EOF
You may wish to add a “Security
session”. For explanations, see
https://www.eecis.udel.edu/~mills/ntp/html/accopt.html#restrict.
cat >> /etc/ntp.conf << "EOF"
# Security session
restrict default limited kod nomodify notrap nopeer noquery
restrict -6 default limited kod nomodify notrap nopeer noquery
restrict 127.0.0.1
restrict ::1
EOF
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-20150304 package.
make install-ntpd
If you prefer to run ntpd periodically, add the
following command to root's
crontab:
ntpd -q
Execute the following command if you would like to set the
hardware clock to the current system time at shutdown and reboot:
ln -v -sf ../init.d/setclock /etc/rc.d/rc0.d/K46setclock &&
ln -v -sf ../init.d/setclock /etc/rc.d/rc6.d/K46setclock
The other way around is already set up by LFS.
Contents
Installed Programs:
calc_tickadj, ntp-keygen, ntp-wait, ntpd,
ntpdate, ntpdc, ntpq, ntptime, ntptrace, sntp and
tickadj
Installed Libraries:
None
Installed Directories:
/usr/share/ntp, /usr/share/doc/ntp-4.2.8
and /var/lib/ntp
Short Descriptions
|
calc_tickadj
|
calculates optimal value for tick given ntp drift file.
|
|
ntp-keygen
|
generates cryptographic data files used by the NTPv4
authentication and identification schemes.
|
|
ntp-wait
|
is useful at boot time, to delay the boot sequence until
ntpd has
set the time.
|
|
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.
|
|
ntptrace
|
traces a chain of ntp servers back to the primary source.
|
|
sntp
|
is a Simple Network Time Protocol (SNTP) client.
|
|
tickadj
|
reads, and optionally modifies, several
timekeeping-related variables in older kernels that do
not have support for precision timekeeping.
|
Last updated on 2015-02-26 20:16:43 -0800