This page describe the installation of NTPd as a server for other clients.

• Download the latest NTPd source and md5 file from: http://www.ntp.org/downloads.html
• Read the changelog: http://archive.ntp.org/ntp4/ChangeLog-stable
• Verify md5 sum:

  # md5sum -c ntp-4.2.8p10.tar.gz.md5 
  ntp-4.2.8p10.tar.gz: OK

• Install development tools, libraries and utilities:

  # yum groupinstall "Development Tools"
  # yum install libcap-devel libevent-devel openssl-devel perl-File-Fetch.noarch

• Stop running the distribution default NTPd:

  # systemctl stop ntpd

• Uninstall NTPd:

  # yum remove ntp

• Exclude ntp packages in yum config:

  # echo "exclude=ntp*" >> /etc/yum.conf

• Remove ntp user:

  # userdel ntp

• Extract NTPd sources:

  # tar zxf ntp-4.2.8p10.tar.gz

• Configure:

  # cd ntp-4.2.8p10
  # ./configure --enable-linuxcaps --docdir=/usr/share/doc/ntp-4.2.8p10

• Compile:

  # make

• Create configuration file /etc/ntp.conf:

  driftfile /var/lib/ntp/drift
  
  restrict default kod nomodify notrap nopeer noquery
  restrict -6 default kod nomodify notrap nopeer noquery
  
  restrict 127.0.0.1 
  restrict ::1
  
  # pick servers near to you!
  server ntp2.polaire.nl iburst
  server ntp0.nl.net iburst
  server ntp1.nl.net iburst
  server ntp.ring.nlnog.net iburst
  
  # Enable writing of statistics records.
  statistics clockstats cryptostats loopstats peerstats
  
  leapfile /var/lib/ntp/leap-seconds.list

• Create group:

  # groupadd ntp

• Create user:

  # useradd -d /var/lib/ntp -g ntp -s /bin/false ntp

• Add /usr/local/bin to path:

  # printf 'PATH=${PATH}:/usr/local/bin\n' > /etc/profile.d/ntp-path.sh

• Create directory:

  # install -v -o ntp -g ntp -d /var/lib/ntp

• Install NTPd:

  # cd ntp-4.2.8p10
  # make install

• Start NTPd:

  # /usr/local/bin/ntpd -g -u ntp:ntp

• Show version:

  # ntpd --version
  ntpd 4.2.8p10@1.3728-o Thu Jun  1 12:37:34 UTC 2017 (1)

Make sure your server can reach time.nist.gov over FTP.

use Digest::SHA qw(sha1_hex); use File::Copy qw(move); use File::Fetch; use Getopt::Long qw(:config auto_help no_ignore_case bundling); use Sys::Syslog;

• Schedule retrieval of leapfile using the update-leap script. For example put the script below in /etc/cron.weekly/leap.sh

  #!/bin/bash
  
  # update leap file if necessary
  /usr/local/bin/update-leap -4 -s ftp://time.nist.gov/pub/leap-seconds.list
  
  # stop ntpd
  /bin/pkill ntpd
  
  # start ntpd
  if /bin/pgrep ntpd >/dev/null; then
    echo "NTP daemon did not stop! Not trying to start another one."
  else
    systemctl start ntpd
  fi

• Create the file: /etc/systemd/system/ntpd.service

  [Unit]
  Description=Network Time Service
  After=syslog.target ntpdate.service sntp.service
  Conflicts=systemd-timesyncd.service
  
  [Service]
  Type=forking
  ExecStart=/usr/local/bin/ntpd -g -u ntp:ntp
  PrivateTmp=true
  
  [Install]
  WantedBy=multi-user.target

• Enable the service at boot:

  systemctl enable ntpd.service

• Start the service:

  systemctl start ntpd.service