1. NTP伺服器搭建

安裝ntp yum install -y ntp

2. 外網使用阿里雲ntp伺服器作為基準

阿里雲ntp伺服器列表：
time1.aliyun.com
time2.aliyun.com
time3.aliyun.com
time4.aliyun.com
time5.aliyun.com
time6.aliyun.com
time7.aliyun.com

先ntpdate檢查能否和以上ntp伺服器通訊。
ntpdate -q time1.aliyun.com

有以下輸出表示正常

server 115.28.122.198, stratum 2, offset 53.490757, delay 0.06709
13 Sep 15:27:48 ntpdate[16092]: step time server 115.28.122.198 offset 53.490757 sec
 

3. 修改配置檔案

vim /etc/ntp.conf 做出以下修改

# 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
 
# 允許1-4網段的伺服器來校時，不允許客戶端來修改，登入ntp伺服器 
restrict 192.168
 
.1.0 mask 255.255.255.0 nomodify notrap
restrict 192.168.2.0 mask 255.255.255.0 nomodify notrap
restrict 192.168.3.0 mask 255.255.255.0 nomodify notrap
restrict 192.168.4.0 mask 255.255.255.0 nomodify notrap
 
 
# 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 time1.aliyun.com
server time2.aliyun.com
server time3.aliyun.com
server time4.aliyun.com
server time5.aliyun.com
server time6.aliyun.com
server time7.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

# Enable Logfile
logfile /var/log/ntp.log

4. 使硬體時間和系統時間一致

修改配置檔案 vim /etc/sysconfig/ntpd 新增

SYNC_HWCLOCK=yes

5. 啟動ntpd服務並檢視狀態

systemctl start ntpd

設定自動啟動

chkconfig ntpd on

等待10-15分鐘後執行 ntpstat 檢視同步狀態

synchronised to NTP server (182.92.12.11) at stratum 3 
   time correct to within 470 ms
   polling server every 64 s
發現已經同步。

執行ntpq -p 檢視與阿里雲ntp伺服器連線狀態

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+time6.aliyun.co 10.137.38.86     2 u   10   64   77   41.139    8.490   1.523
-time4.aliyun.co 10.137.38.86     2 u    5   64   77    3.479   15.026   1.354
*time5.aliyun.co 10.137.38.86     2 u   10   64   77   37.243   10.643   1.554
+120.25.115.19   10.137.38.86     2 u    5   64   77    3.574    5.228   2.803

*表示目前正在使用的上層NTP，+表示已連線,可提供時間更新的候補伺服器

執行一下 hwclock --systohc 使系統時間和硬體時間一致。

6. 開啟防火牆

由於ntp服務使用 123埠udp協議 所以需要開啟防火牆。
執行firewall-cmd --zone=public --add-port=123/udp --permanent之後，再執行firewall-cmd --reload。

7. Linux 客戶端使用ntpd服務同步時間

先安裝ntp服務執行yum install -y ntp

修改配置檔案 vim /etc/ntp.conf 修改server，新增日誌

# 允許ntpserver主動修改客戶端時間
restrict 192.168.1.85 nomodify notrap noquery
restrict 192.168.1.50 nomodify notrap noquery

server 192.168.1.85
server 182.168.1.50

logfile /var/log/ntp.log

其他保持預設。

啟動 ntpd服務systemctl start ntpd

開啟本地放火牆 123 UDP埠

執行 ntpq -p 檢視與伺服器連線狀態。

    remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+192.168.1.50    182.92.12.11     3 u   31   64   77    0.189  -30.963  42.392
*192.168.1.85    182.92.12.11     3 u   43   64   77    0.190   -1.903  18.890
 LOCAL(0)        .LOCL.          10 l   60   64   77    0.000    0.000   0.000

執行 ntpstat 檢視同步狀態

synchronised to NTP server (192.168.1.85) at stratum 4
time correct to within 131 ms
polling server every 64 s

8 Windows 使用客戶端同步

8.1 組策略配置

win+r 執行gpedit.msc 啟用全域性配置

啟用ntp客戶端

win+r 執行 gpupdate /force

8.2. 使用自動配置工具

執行自動配置工具，做以下配置，多個伺服器用空格隔開。

之後在系統時間日期內執行同步檢視結果。