在现在跨主机集群大行其道的时代里，在使用多台Linux服务器过程中，保持时间的一致尤为重要。时长发现跨主机的软件集群发生莫名其妙的问题，大多数的时候都会和时间不一致有关系。像Hadoop、Oracle RAC等主流集群软件在部署前都是需要配置NTP服务。这篇文章简单介绍一下NTP的快捷配置，没有原理分析，只是快捷部署手册。
NTP安装
- 首先通过
rpm -qa | grep ntp检查ntp是否已经安装。 - 如果操作系统中没有按照ntp，则按照如下步骤进行安装：
[root@bigdata2 yum.repos.d]# yum install ntp
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* c7-media:
Resolving Dependencies
--> Running transaction check
---> Package ntp.x86_64 0:4.2.6p5-25.el7_3.2 will be installed
--> Processing Dependency: ntpdate = 4.2.6p5-25.el7_3.2 for package: ntp-4.2.6p5-25.el7_3.2.x86_64
--> Processing Dependency: libopts.so.25()(64bit) for package: ntp-4.2.6p5-25.el7_3.2.x86_64
--> Running transaction check
---> Package autogen-libopts.x86_64 0:5.18-5.el7 will be installed
---> Package ntpdate.x86_64 0:4.2.6p5-25.el7_3.2 will be installed
--> Finished Dependency Resolution
Dependencies Resolved
=============================================================================================================================
Package Arch Version Repository Size
=============================================================================================================================
Installing:
ntp x86_64 4.2.6p5-25.el7_3.2 c7-media 547 k
Installing for dependencies:
autogen-libopts x86_64 5.18-5.el7 c7-media 66 k
ntpdate x86_64 4.2.6p5-25.el7_3.2 c7-media 86 k
Transaction Summary
=============================================================================================================================
Install 1 Package (+2 Dependent packages)
Total download size: 699 k
Installed size: 1.6 M
Is this ok [y/d/N]: y
Downloading packages:
-----------------------------------------------------------------------------------------------------------------------------
Total 4.7 MB/s | 699 kB 00:00:00
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Installing : ntpdate-4.2.6p5-25.el7_3.2.x86_64 1/3
Installing : autogen-libopts-5.18-5.el7.x86_64 2/3
Installing : ntp-4.2.6p5-25.el7_3.2.x86_64 3/3
Verifying : autogen-libopts-5.18-5.el7.x86_64 1/3
Verifying : ntp-4.2.6p5-25.el7_3.2.x86_64 2/3
Verifying : ntpdate-4.2.6p5-25.el7_3.2.x86_64 3/3
Installed:
ntp.x86_64 0:4.2.6p5-25.el7_3.2
Dependency Installed:
autogen-libopts.x86_64 0:5.18-5.el7 ntpdate.x86_64 0:4.2.6p5-25.el7_3.2
Complete!
NTP配置
编辑/etc/ntp.conf文件
- 开启指定网段主机的查询权限
restrict 192.168.56.0 mask 255.255.255.0 nomodify notrap
- 关闭外网中的时间服务器同步
#server 0.rhel.pool.ntp.org iburst
#server 1.rhel.pool.ntp.org iburst
#server 2.rhel.pool.ntp.org iburst
#server 3.rhel.pool.ntp.org iburst
- 备选本地主机为时间服务器
server 127.127.1.0
fudge 127.127.1.0 stratum 10
编辑/etc/sysconfig/ntpd文件
启用硬件与软件时钟同步
SYNC_HWCLOCK=yes
NTPD服务管理
启动ntpd服务
[root@bigdata2 etc]# systemctl status ntpd
鈼? ntpd.service - Network Time Service
Loaded: loaded (/usr/lib/systemd/system/ntpd.service; disabled; vendor preset: disabled)
Active: inactive (dead)
[root@bigdata2 etc]# systemctl start ntpd
[root@bigdata2 etc]# systemctl status ntpd
鈼? ntpd.service - Network Time Service
Loaded: loaded (/usr/lib/systemd/system/ntpd.service; disabled; vendor preset: disabled)
Active: active (running) since Tue 2019-04-30 18:10:38 EDT; 2s ago
Process: 6429 ExecStart=/usr/sbin/ntpd -u ntp:ntp $OPTIONS (code=exited, status=0/SUCCESS)
Main PID: 6430 (ntpd)
CGroup: /system.slice/ntpd.service
鈹斺攢6430 /usr/sbin/ntpd -u ntp:ntp -g
Apr 30 18:10:38 bigdata2 ntpd[6430]: Listen normally on 4 enp0s8 192.168.56.112 UDP 123
Apr 30 18:10:38 bigdata2 ntpd[6430]: Listen normally on 5 enp0s9 192.168.1.105 UDP 123
Apr 30 18:10:38 bigdata2 ntpd[6430]: Listen normally on 6 lo ::1 UDP 123
Apr 30 18:10:38 bigdata2 ntpd[6430]: Listen normally on 7 enp0s3 fe80::203a:18c4:d21b:2e8b UDP 123
Apr 30 18:10:38 bigdata2 ntpd[6430]: Listen normally on 8 enp0s8 fe80::baba:398f:4ef6:b039 UDP 123
Apr 30 18:10:38 bigdata2 ntpd[6430]: Listening on routing socket on fd #25 for interface updates
Apr 30 18:10:38 bigdata2 ntpd[6430]: 0.0.0.0 c016 06 restart
Apr 30 18:10:38 bigdata2 ntpd[6430]: 0.0.0.0 c012 02 freq_set kernel 0.000 PPM
Apr 30 18:10:38 bigdata2 ntpd[6430]: 0.0.0.0 c011 01 freq_not_set
Apr 30 18:10:39 bigdata2 ntpd[6430]: 0.0.0.0 c514 04 freq_mode
设置开机启动ntpd服务
[root@bigdata2 etc]# chkconfig ntpd
Note: Forwarding request to 'systemctl is-enabled ntpd.service'.
disabled
[root@bigdata2 etc]# chkconfig ntpd on
Note: Forwarding request to 'systemctl enable ntpd.service'.
Created symlink from /etc/systemd/system/multi-user.target.wants/ntpd.service to /usr/lib/systemd/system/ntpd.service.
[root@bigdata2 etc]# chkconfig ntpd
Note: Forwarding request to 'systemctl is-enabled ntpd.service'.
enabled
客户端主机配置
配置定时时间同步作业
crontab -e
*/10 * * * * /usr/sbin/ntpdate bigdata2