1、三个节点时间同步，cdh1,cdh2,cdh3
2、做法：cdh1从网络时间同步，然后cdh2和cdh3从cdh1节点同步
3、安装与自启动设置
yum install ntp
按上面的安装方式在内网每台节点上都安装好NTP软件包
完成后，都需要配置NTP服务为自启动
chkconfig ntpd on
chkconfig --list ntpd
ntpd 0:关闭 1:关闭 2:启用 3:启用 4:启用 5:启用 6:关闭
如果2,3,4,5都为启动，则正常。
在配置前，先使用ntpdate手动同步下时间，免得本机与外部时间服务器时间差距太大，让ntpd不能正常同步。
ntpdate -u cn.ntp.org.cn
4、配置cdh1的/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. # 允许内网其他机器同步时间 restrict 192.168.189.0 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 cn.ntp.org.cn perfer #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 cn.ntp.org.cn 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
5、启动ntp服务
service ntpd start
启动后，一般需要5-10分钟左右的时候才能与外部时间服务器开始同步时间。
6、通过watch ntpq -p 查看网络ntp服务器
7、然后去cdh2和cdh3去修改/ect/ntp.conf,向cdh1同步时间
修改一行：server cdh1
8、分别在cdh2和cdh3启动ntp
service ntpd start
9、其他命令
service ntpd restart 重启ntp
service ntpd stop 停止ntp
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
[root@cdh2 opt]# ntpstat
synchronised to NTP server (192.168.189.128) at stratum 4
time correct to within 48 ms
polling server every 64 s