categories:

• Howto
• Linux
• Security

Install the package : yum install ntp

Make a backup of the default config cp /etc/ntp.conf /etc/ntp.conf.default

Minimal and pretty safe /etc/ntp.conf : server 0.europe.pool.ntp.org server 1.europe.pool.ntp.org server 2.europe.pool.ntp.org server 0.north-america.pool.ntp.org server 1.north-america.pool.ntp.org server 2.north-america.pool.ntp.org driftfile /var/lib/ntp/drift restrict default nopeer nomodify restrict 127.0.0.1

Make sure NTP daemon will start at boot : chkconfig ntpd on

Start the NTP service : service ntpd on

Verify if your server can reach the peers : `# ntpq -pn remote refid st t when poll reach delay offset jitter

195.190.190.13 129.132.97.15 3 u 33 64 3 31.031 -46784. 0.540 204.152.189.171 216.218.254.202 2 u 33 64 3 160.121 -46786. 0.490 213.144.132.251 192.36.134.17 2 u 31 64 3 46.861 -46782. 3.868 127.127.1.0 LOCAL(0) 10 l 30 64 3 0.000 0.000 0.001`

The port udp/123 should be opened in the router routing to the internet. Logs can be found under /var/log/messages