当我们需要管理多台服务器的时间时，一台一台的修改未免太麻烦了，NTP服务就很好的为我们解决了这个问题！

1.首先安装NTP

[root@localhost /]# yum install ntp -y

2.修改NTP配置文件，添加NTP服务器的网络位置    /etc/ntp.conf

# For more information about this file, see the man pages# ntp.conf(5), ntp_acc(5), ntp_auth(5), ntp_clock(5), ntp_misc(5), ntp_mon(5).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 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 127.0.0.1restrict ::1# Hosts on local network are less restricted.#restrict 192.168.1.0 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).server 192.168.1.1 iburst       #目标服务器网络位置#server 1.centos.pool.ntp.org iburst     #一下三个是CentOS官方的NTP服务器，我们注释掉#server 2.centos.pool.ntp.org iburst#server 3.centos.pool.ntp.org iburst#broadcast 192.168.1.255 autokey        # broadcast server#broadcastclient                        # broadcast client#broadcast 224.0.1.1 autokey            # multicast server#multicastclient 224.0.1.1              # multicast client#manycastserver 239.255.254.254         # manycast server#manycastclient 239.255.254.254 autokey # manycast client# Enable public key cryptography.#cryptoincludefile /etc/ntp/crypto/pw# Key file containing the keys and key identifiers used when operating# with symmetric key cryptography.keys /etc/ntp/keys# Specify the key identifiers which are trusted.#trustedkey 4 8 42# Specify the key identifier to use with the ntpdc utility.#requestkey 8# Specify the key identifier to use with the ntpq utility.#controlkey 8# Enable writing of statistics records.#statistics clockstats cryptostats loopstats peerstats# Disable the monitoring facility to prevent amplification attacks using ntpdc# monlist command when default restrict does not include the noquery flag. See# CVE-2013-5211 for more details.# Note: Monitoring will not be disabled with the limited restriction flag.disable monitor

保存退出

3.启动服务并设置开启自启

[root@localhost /]# systemctl start ntpd.service　　#启动服务 [root@localhost /]# systemctl enable ntpd.service　　#设置为开机启动

4.查看运行状态

[root@localhost /]# systemctl status ntpd.service

● ntpd.service - Network Time Service

   Loaded: loaded (/usr/lib/systemd/system/ntpd.service; enabled; vendor preset: disabled)

   Active: active (running) since 二 2016-10-11 13:34:11 CST; 8min ago

 Main PID: 6497 (ntpd)

   CGroup: /system.slice/ntpd.servicess

           └─6497 /usr/sbin/ntpd -u ntp:ntp -g

10月 11 13:34:11 localhost.localdomain ntpd[6497]: Listen and drop on 1 v6wildcard :: UDP 123

10月 11 13:34:11 localhost.localdomain ntpd[6497]: Listen normally on 2 lo 127.0.0.1 UDP 123

10月 11 13:34:11 localhost.localdomain ntpd[6497]: Listen normally on 3 eno16777736 192.168.100.100 UDP 123

可以看到当前的状态为 running