一、NTP服务器介绍
网络时间协议（Network Time Protocol，NTP）服务器，也就是日常所说的NTP服务器，用来提供同步时间服务。在生产环境中，很多人都会忽略时间问题，实际上服务器、网络设备等，特别是Linux操作系统和虚拟化平台的时间不同步会导致很多问题。那么搭建一台NTP服务器就非常重要，生产环境中的设备可以直接与NTP服务器进行时间同步，NTP服务器本身也可以访问互连的NTP服务器进行同步。NTP服务器可以是物理服务器，也可以是虚拟机。
二、安装NTP服务组件
在Linux服务器（如，CentOS、Ubuntu等操作系统）上，使用命令进行安装。
本实验以CentOS 7 Linux环境进行演示操作记录。
YUM源已更新成阿里云开源镜像站里的CentOS镜像，加速快捷访问。
[root@ntp ~]# yum clean all Loaded plugins: fastestmirror Cleaning repos: base extras updates Cleaning up list of fastest mirrors [root@ntp ~]# yum repolist Loaded plugins: fastestmirror Determining fastest mirrors * base: mirrors.aliyun.com * extras: mirrors.aliyun.com * updates: mirrors.aliyun.com base | 3.6 kB 00:00:00 extras | 2.9 kB 00:00:00 updates | 2.9 kB 00:00:00 (1/4): base/7/x86_64/group_gz | 153 kB 00:00:00 (2/4): extras/7/x86_64/primary_db | 243 kB 00:00:00 (3/4): updates/7/x86_64/primary_db | 12 MB 00:00:01 (4/4): base/7/x86_64/primary_db | 6.1 MB 00:00:03 repo id repo name status base/7/x86_64 CentOS-7 - Base - mirrors.aliyun.com 10,072 extras/7/x86_64 CentOS-7 - Extras - mirrors.aliyun.com 500 updates/7/x86_64 CentOS-7 - Updates - mirrors.aliyun.com 2,963 repolist: 13,535 [root@ntp ~]#
执行yum install -y ntp命令，进行ntp组件安装。
[root@ntp ~]# yum install -y ntp Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: mirrors.aliyun.com * extras: mirrors.aliyun.com * updates: mirrors.aliyun.com Resolving Dependencies --> Running transaction check ---> Package ntp.x86_64 0:4.2.6p5-29.el7.centos.2 will be installed --> Processing Dependency: ntpdate = 4.2.6p5-29.el7.centos.2 for package: ntp-4.2.6p5-29.el7.centos.2.x86_64 --> Processing Dependency: libopts.so.25()(64bit) for package: ntp-4.2.6p5-29.el7.centos.2.x86_64 --> Running transaction check ---> Package autogen-libopts.x86_64 0:5.18-5.el7 will be installed ---> Package ntpdate.x86_64 0:4.2.6p5-29.el7.centos.2 will be installed --> Finished Dependency Resolution Dependencies Resolved ================================================================================================================= Package Arch Version Repository Size ================================================================================================================= Installing: ntp x86_64 4.2.6p5-29.el7.centos.2 base 549 k Installing for dependencies: autogen-libopts x86_64 5.18-5.el7 base 66 k ntpdate x86_64 4.2.6p5-29.el7.centos.2 base 87 k Transaction Summary ================================================================================================================= Install 1 Package (+2 Dependent packages) Total download size: 701 k Installed size: 1.6 M Downloading packages: (1/3): autogen-libopts-5.18-5.el7.x86_64.rpm | 66 kB 00:00:00 (2/3): ntpdate-4.2.6p5-29.el7.centos.2.x86_64.rpm | 87 kB 00:00:00 (3/3): ntp-4.2.6p5-29.el7.centos.2.x86_64.rpm | 549 kB 00:00:00 ----------------------------------------------------------------------------------------------------------------- Total 1.7 MB/s | 701 kB 00:00:00 Running transaction check Running transaction test Transaction test succeeded Running transaction Installing : autogen-libopts-5.18-5.el7.x86_64 1/3 Installing : ntpdate-4.2.6p5-29.el7.centos.2.x86_64 2/3 Installing : ntp-4.2.6p5-29.el7.centos.2.x86_64 3/3 Verifying : ntpdate-4.2.6p5-29.el7.centos.2.x86_64 1/3 Verifying : ntp-4.2.6p5-29.el7.centos.2.x86_64 2/3 Verifying : autogen-libopts-5.18-5.el7.x86_64 3/3 Installed: ntp.x86_64 0:4.2.6p5-29.el7.centos.2 Dependency Installed: autogen-libopts.x86_64 0:5.18-5.el7 ntpdate.x86_64 0:4.2.6p5-29.el7.centos.2 Complete! [root@ntp ~]#
三、配置阿里云镜像站NTP服务
配置之前，测试服务器是否能够访问到阿里云NTP服务器。
ping ntp.aliyun.com -c 5
修改/etc/ntp.conf配置文件。
注释掉原来配置文件中的NTP服务器地址，添加阿里云NTP服务器地址。
[root@ntp ~]# vi /etc/ntp.conf [root@ntp ~]# 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. 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 127.0.0.1 restrict ::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 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 ntp.aliyun.com #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 # 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 [root@ntp ~]#
四、启动NTP服务
启动ntp服务
systemctl start ntpd
设置ntp服务开机自启动
systemctl enable ntpd
查看ntp服务是否正常
systemctl status ntpd
[root@ntp ~]# systemctl start ntpd [root@ntp ~]# systemctl enable ntpd Created symlink from /etc/systemd/system/multi-user.target.wants/ntpd.service to /usr/lib/systemd/system/ntpd.service. [root@ntp ~]# systemctl status ntpd ● ntpd.service - Network Time Service Loaded: loaded (/usr/lib/systemd/system/ntpd.service; enabled; vendor preset: disabled) Active: active (running) since Sun 2021-11-28 19:06:34 CST; 23h left Main PID: 1988 (ntpd) CGroup: /system.slice/ntpd.service └─1988 /usr/sbin/ntpd -u ntp:ntp -g Nov 28 19:06:34 ntp ntpd[1988]: Listen normally on 3 ens32 192.168.1.50 UDP 123 Nov 28 19:06:34 ntp ntpd[1988]: Listen normally on 4 lo ::1 UDP 123 Nov 28 19:06:34 ntp ntpd[1988]: Listen normally on 5 ens32 fe80::e4b:3ef:613c:8741 UDP 123 Nov 28 19:06:34 ntp ntpd[1988]: Listening on routing socket on fd #22 for interface updates Nov 28 19:06:34 ntp ntpd[1988]: 0.0.0.0 c016 06 restart Nov 28 19:06:34 ntp ntpd[1988]: 0.0.0.0 c012 02 freq_set kernel 0.000 PPM Nov 28 19:06:34 ntp ntpd[1988]: 0.0.0.0 c011 01 freq_not_set Nov 28 19:09:51 ntp ntpd[1988]: 0.0.0.0 c61c 0c clock_step -86398.982768 s Nov 27 19:09:52 ntp ntpd[1988]: 0.0.0.0 c614 04 freq_mode Nov 27 19:09:53 ntp ntpd[1988]: 0.0.0.0 c618 08 no_sys_peer [root@ntp ~]#
五、查看NTP源
ntpq -p
即[203.107.6.88]地址为阿里云NTP服务器的IP地址。
[root@ntp ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
203.107.6.88 100.107.25.114 2 u 56 64 7 13.685 -0.002 0.415
六、查看NTP服务状态
# 输出如下内容，表示在同步中，需要耐心等待一下 [root@ntp ~]# ntpstat unsynchronised time server re-starting polling server every 8 s # 输出如下内容，表示同步成功 [root@ntp ~]# ntpstat synchronised to NTP server (203.107.6.88) at stratum 3 time correct to within 958 ms polling server every 64 s
七、将客户端与NTP服务器同步
[root@client ~]# ntpdate -d 192.168.1.50 28 Nov 19:37:54 ntpdate[2880]: ntpdate 4.2.6p5@1.2349-o Tue Jun 23 15:38:19 UTC 2020 (1) Looking for host 192.168.1.50 and service ntp host found : 192.168.1.50 transmit(192.168.1.50) receive(192.168.1.50) transmit(192.168.1.50) receive(192.168.1.50) transmit(192.168.1.50) receive(192.168.1.50) transmit(192.168.1.50) receive(192.168.1.50) server 192.168.1.50, port 123 stratum 3, precision -25, leap 00, trust 000 refid [192.168.1.50], delay 0.02652, dispersion 0.00000 transmitted 4, in filter 4 reference time: e54c9534.6f868aa9 Sat, Nov 27 2021 19:29:56.435 originate timestamp: e54c9719.4617ce7f Sat, Nov 27 2021 19:38:01.273 transmit timestamp: e54de898.b45bc870 Sun, Nov 28 2021 19:38:00.704 filter delay: 0.02658 0.02655 0.02652 0.02660 0.00000 0.00000 0.00000 0.00000 filter offset: -86399.4 -86399.4 -86399.4 -86399.4 0.000000 0.000000 0.000000 0.000000 delay 0.02652, dispersion 0.00000 offset -86399.431479 28 Nov 19:38:00 ntpdate[2880]: step time server 192.168.1.50 offset -86399.431479 sec [root@client ~]#
八、将系统时间同步到硬件
[root@client ~]# hwclock -w [root@client ~]# date Sun Nov 28 19:39:10 CST 2021
