内网搭建ntp时间同步服务器
在公司内网，搭建服务器集群时，为了到达一致性，需要对服务器时间进行同步。内网一般不能访问互联网，此时急需一台内部的时间服务器，用于内网机器的时间同步。
环境：
操作系统：Centos6.6
ntpd服务器：192.168.113.159
客户端服务器：192.168.113.183
1. 安装ntpd(ntpd服务器)
[root@localhost ~]# yum install ntpd -y
2. 修改配置文件
[root@localhost ~]# vim /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 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.
restrict 127.0.0.1
restrict -6 ::1
# Hosts on local network are less restricted.
#restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
#允许设置的可信任地址段对NTPD各服务的访问，但不允许此地址段内客户端修改NTPD服务器时间（nomodify）
restrict 192.168.113.0 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).
#注释掉网络服务器
#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
#设置本地时间服务器
service 192.168.113.159
# 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
fudge 127.127.1.0 stratum 5
#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.
#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. 启动服务，设置开机自启动
[root@localhost ~]# chkconfig --level 345 ntpd on
[root@localhost ~]# service ntpd restart
关闭 ntpd： [确定]
正在启动 ntpd： [确定]
4. 客户端测试
template:/root>/usr/sbin/ntpdate 192.168.113.159
28 Feb 02:44:50 ntpdate[5235]: step time server 192.168.113.159 offset -52476.869449 sec
5. 客户端配置定时任务
[root@ansible named]#vim /usr/bin/ntpsync.sh
#!/bin/bash
/usr/sbin/ntpdate 192.168.113.159
#同步系统时间到硬件时间
/sbin/hwclock –w
[root@ansible named]#crontab -e
#sync time with ntpserver at 12:00
0 12 * * * /usr/bin/ntpsync.sh