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NTP：是Network Time Protocol的缩写又 称网络时间协议，是用来使计算机时间同步化的一种协议，用来同步网络中各主机的时 间，在linux系统中早期使用ntp来实现，后来使用chrony来实现。Chrony 应用本身已经有 几年了，是网络时间协议的 (NTP) 的另一种实现。
一、安装ntp服务
1、首先检查系统中是否安装ntp包：rpm -q ntp
2、执行命令在线安装ntp：yum -y install ntp
3、现在设置开机自启动：systemctl enable ntpd
二、配置ntp服务
时间服务器配置： vim /etc/ntp.conf
在文本中添加（/！！！前为要添加的内容）
# For more information about this file, see the ntp.conf(5) man page.# Record the frequency of the system clock.
driftfile /var/lib/ntp/drift# Permit time synchronization with our time source, but do not
# permit the source to query or modify the service on this system.
restrict default nomodify notrap nopeer noepeer noquery# Permit association with pool servers.
restrict source nomodify notrap noepeer noquery# Permit all access over the loopback interface. This could
# be tightened as well, but to do so would effect some of
# the administrative functions.
restrict 192.168.29.28 nomodify notrap nopeer noquery //！！！
restrict 127.0.0.1
restrict ::1# Hosts on local network are less restricted.
restrict 192.168.1.2 mask 255.255.255.0 nomodify notrap //！！！# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
# pool 2.openEuler.pool.ntp.org iburst
server 127.127.1.0 //！！！
Fudge 127.127.1.0 stratum 10 //！！！# Reduce the maximum number of servers used from the pool.
tos maxclock 5# Enable public key cryptography.
# crypto
1）启动ntp服务
service ntpd start
systemctl restart ntpd.service
2）通过命令timedatectl查看，ntp服务是否生效
（若NTP enabled: no，执行命令timedatectl set-ntp yes）
3）查看ntp服务器有无和上层ntp连通
4）查看ntp服务器与上层ntp的状态
