Configuring the NTP time server

I. Installing the NTP software

1. Check if the NTP-related package is installed.

Rpm-qa | grep NTP

2. Install the NTP software.

Yum-y Install NTP

Two. Parameter explanation

Ignore: Turn off all NTP Online Services

Nomodify: The client cannot change the time parameters on the server side, but the client can perform the network calibration via the server.

Notrust: The client source will be treated as untrusted subnet unless authenticated

Noquery: No time query for clients: Client cannot query NTP server using commands such as Ntpq,ntpc

Notrap: Do not provide trap remote login: Deny the matching host to provide mode 6 control message Trap Service. The Trap service is a subsystem of the NTPDQ Control Message Protocol, which is used for remote event logger applications.

Nopeer: Used to prevent the host from attempting to peer to the server and allow the fraudulent server to control the clock

Kod: The Kod package is sent when an access violation occurs.

Three. Modify the configuration file

1. View the unmodified configuration file

# grep ^[^#]/etc/ntp.conf

Driftfile/var/lib/ntp/drift

Restrict default nomodify notrap nopeer noquery

Restrict 127.0.0.1

Restrict:: 1

Server 0.centos.pool.ntp.org Iburst

Server 1.centos.pool.ntp.org Iburst

Server 2.centos.pool.ntp.org Iburst

Server 3.centos.pool.ntp.org Iburst

Includefile/etc/ntp/crypto/pw

Keys/etc/ntp/keys

Disable Monitor

1. Set allow clients of any IP to have time synchronization (modified configuration file)

# grep ^[^#]/etc/ntp.conf

Driftfile/var/lib/ntp/drift

Restrict default nomodify Notrap

Restrict 127.0.0.1

Restrict:: 1

Server 0.centos.pool.ntp.org Iburst

Server 1.centos.pool.ntp.org Iburst

Server 2.centos.pool.ntp.org Iburst

Server 3.centos.pool.ntp.org Iburst

Includefile/etc/ntp/crypto/pw

Keys/etc/ntp/keys

Disable Monitor

2. Allow time synchronization for clients of 192.168.1.0 network segment only (modified configuration file)

# grep ^[^#]/etc/ntp.conf

Driftfile/var/lib/ntp/drift

Restrict default nomodify notrap nopeer noquery

Restrict 127.0.0.1

Restrict:: 1

Restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap

Server 0.centos.pool.ntp.org Iburst

Server 1.centos.pool.ntp.org Iburst

Server 2.centos.ntp.org Iburst

Server 3.centos.pool.ntp.org Iburst

Includefile/etc/ntp/crypto/pw

Keys/etc/ntp/keys

Disable Monitor

Four. Start the NTP service and firewall

Systemctl Start NTPD

Systemctl Enable NTPD

Iptables-a input-p udp-i eno16777736-s 192.168.1.0/24--dport 123-j ACCEPT

Setsebool-p Ntp_disable_trans 1#selinux Settings

vi/etc/sysconfig/ntpd# allows the BIOS to synchronize with the system time, adding the following line.

Sync_hwclock=yes

Five. Detecting NTP

1. Detect if the NTP service is running

# NETSTAT-TLUNP | grep NTP

UDP 0 0 192.168.1.101:123 0.0.0.0:* 2563/ntpd

UDP 0 0 127.0.0.1:123 0.0.0.0:* 2563/ntpd

UDP 0 0 0.0.0.0:123 0.0.0.0:* 2563/ntpd

UDP6 0 0 fe80::20c:29ff:fe7b:123:::* 2563/ntpd

UDP6 0 0:: 1:123:::* 2563/ntpd

UDP6 0 0::: 123:::* 2563/ntpd

2. Check to see if the NTP server is connected to the upper NTP

# Ntpstat

Synchronised to NTP server (120.25.108.11) at Stratum 3

Time correct to within MS

Polling server every S

3. View the status of the NTP server and the upper NTP

# ntpq-p

Remote refID St T when poll reach delay offset jitter

==============================================================================

news.neu.edu.cn.          Init. u-64 0 0.000 0.000 0.000

x202.118.1.130 202.118.1.47 2 U 7 64 377 153.659 9.605 19.941

*time4.aliyun.co 10.137.38.86 2 U 10 64 377 39.666-47.661 15.944

Remote-the IP or hostname of the native and upper NTP, "+" is preferred, "*" indicates a secondary priority

refID-refer to the previous level of NTP host address

St-stratum stratum

When-how many seconds ago the time has been synchronized

Poll-How many seconds after the next update

Reach-Number of times an update has been requested to the upper NTP server

Delay-Network latency

Offset-time compensation

Jitter-system time vs. BIOS difference

Six. Configure the time synchronization client

1. Execute the ntpdate command:

Ntpdate 192.168.1.101 #192.168.1.101 as the NTP server IP address

2. Write to Bios

Hclock-w

3.crond Service

Vi/etc/crontab

8 * * * root/usr/sbin/ntpdate 192.168.1.101; /sbin/hwclock-w

4. Restart the Crond service

Service Crond Restart

Configuring the NTP time server