參考連結：
阿里巴巴開源映象站
NTP下載安裝教程

一、NTP伺服器介紹

網路時間協議（Network Time Protocol，NTP）伺服器，也就是日常所說的NTP伺服器，用來提供同步時間服務。在生產環境中，很多人都會忽略時間問題，實際上伺服器、網路裝置等，特別是Linux作業系統和虛擬化平臺的時間不同步會導致很多問題。那麼搭建一臺NTP伺服器就非常重要，生產環境中的裝置可以直接與NTP伺服器進行時間同步，NTP伺服器本身也可以訪問互連的NTP伺服器進行同步。NTP伺服器可以是物理伺服器，也可以是虛擬機器。

二、安裝NTP服務元件

在Linux伺服器（如，CentOS、Ubuntu等作業系統）上，使用命令進行安裝。
本實驗以CentOS 7 Linux環境進行演示操作記錄。

YUM源已更新成阿里雲開源映象站裡的CentOS映象，加速快捷訪問。

[root@ntp ~]# yum clean allLoaded plugins: fastestmirror
Cleaning repos: base extras updates
Cleaning up list of fastest mirrors
[root@ntp ~]# yum repolistLoaded 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 ~]#

執行 yum install -y ntp命令，進行ntp元件安裝。

[root@ntp ~]# yum install -y ntpLoaded 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 testTransaction 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、配置阿里雲映象站NTP服務

配置之前，測試伺服器是否能夠訪問到阿里雲NTP伺服器。

ping ntp.aliyun.com -c 5

修改 /etc/ntp.conf配置檔案。

註釋掉原來配置檔案中的NTP伺服器地址，新增阿里雲NTP伺服器地址。

[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 ().#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 iburstserver 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.#cryptoincludefile /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、啟動NTP服務

啟動ntp服務
systemctl start ntpd
設定ntp服務開機自啟動
systemctl enable ntpd
檢視ntp服務是否正常
systemctl status ntpd

[root@ntp ~]# systemctl start ntpd[root@ntp ~]# systemctl enable ntpdCreated 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 updatesNov 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、檢視NTP源

ntpq -p

即[203.107.6.88]地址為阿里雲NTP伺服器的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、檢視NTP服務狀態

# 輸出如下內容，表示在同步中，需要耐心等待一下[root@ntp ~]# ntpstatunsynchronised
  time server re-starting
   polling server every 8 s# 輸出如下內容，表示同步成功[root@ntp ~]# ntpstatsynchronised to NTP server (203.107.6.88) at stratum 3
   time correct to within 958 ms
   polling server every 64 s

七、將客戶端與NTP伺服器同步

[root@client ~]# ntpdate -d 192.168.1.5028 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、將系統時間同步到硬體

[root@client ~]# hwclock -w[root@client ~]# dateSun Nov 28 19:39:10 CST 2021

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