1、NTP服务安装
# 系统自带ntp
rpm -qa ntp
[root@moban ~]# rpm -qa ntp ntp-4.2.6p5-10.el6.centos.2.x86_64
# 可以更新一下系统自带的ntp服务
yum -y install ntp
# 如果没有就安装
yum -y install ntp
2、配置NTP服务
备份配置文件
cp /etc/ntp.conf{,.ori}
配置文件详解
[root@node1 ~]# cat /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.
#下面两行默认是拒绝所有来源的任何访问 要注释掉
#restrict default kod nomodify notrap nopeer noquery
#restrict -6 default kod 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.
#ntpd 需要有 loopback 的参与，而默认是拒绝所有，将 loopback 放行就好了
restrict 127.0.0.1 #开放本机的任何访问
restrict -6 ::1
# 允许内网其他机器同步时间
# Hosts on local network are less restricted.
restrict 172.16.31.0 mask 255.255.0.0 nomodify notrap
# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
# 注释掉默认的 这里参数指时间服务器向谁同步时间 一般指定国内时间服务器
#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
server ntp1.aliyun.com
server time.nist.gov
server 172.16.0.1
#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
# 允许上层时间服务器主动修改本机时间
restrict 172.16.0.1 nomodify notrap noquery
# 外部时间服务器不可用时，以本地时间作为时间服务
server 127.127.1.0 #local clock
fudge 127.127.1.0 stratum 10
# Enable public key cryptography.
#crypto
includefile /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
3、启动NTP服务器
/etc/init.d/ntpd start
检查时间服务
ntpq -p
[root@lb01 ~]# ntpq -p remote refid st t when poll reach delay offset jitter ============================================================================== 120.25.115.20 10.137.53.7 2 u 18 64 1 35.093 906.240 0.000 time-c-wwv.nist .INIT. 16 u - 64 0 0.000 0.000 0.000
4、客户端时间同步测试
ntpdate ntp时间服务器的IP地址
ntpdate 172.16.1.5
5、注意事项
# 如果计划任务有时间同步，先注释，两种用法会冲突。
[root@lb01 ~]# crontab -l #time sync 2018-08-19 #*/10 * * * * /usr/sbin/ntpdate ntp1.aliyun.com &>/dev/null
ntpstat 命令查看时间同步状态，这个一般需要5-10分钟后才能成功连接和同步。所以，服务器启动后需要稍等下。
[root@lb01 ~]# ntpstat unsynchronised time server re-starting polling server every 8 s
正常应该显示：
[root@lb01 ~]# ntpstat synchronised to local net at stratum 11 time correct to within 3948 ms polling server every 64 s