CentOS7搭建NTP服务器及客户端同步时间

一、服务器配置

1、查看服务器、客户端操作系统版本

[root@hadoop101 ~]# cat /etc/redhat-release
CentOS Linux release 7.6. (Core) 

2、查看服务器是否安装ntp，系统默认安装ntpdate；

[root@hadoop101 ~]# rpm -qa | grep ntp
fontpackages-filesystem-1.44-.el7.noarch
ntpdate-4.2.6p5-.el7.centos.x86_64
python-ntplib-0.3.-.el7.noarch
ntp-4.2.6p5-.el7.centos.x86_64

3、安装ntp ntpdate，其中ntpdate默认安装，可以只安装ntp；

yum install ntp ntpdate -y

4、查看是否已安装完成，与第2步对比

[root@hadoop101 mysql-libs]# rpm -qa | grep ntp
fontpackages-filesystem-1.44-.el7.noarch
ntpdate-4.2.6p5-.el7.centos.x86_64
ntp-4.2.6p5-.el7.centos.x86_64
python-ntplib-0.3.-.el7.noarch

5、查看ntp服务器状态，两条命令效果一样

[root@hadoop101 ~]# systemctl status ntpd
● ntpd.service - Network Time Service
Loaded: loaded (/usr/lib/systemd/system/ntpd.service; disabled; vendor preset: disabled)
Active: inactive (dead)

或

[root@hadoop101 ~]# service ntpd status
Redirecting to /bin/systemctl status ntpd.service
● ntpd.service - Network Time Service
Loaded: loaded (/usr/lib/systemd/system/ntpd.service; disabled; vendor preset: disabled)
Active: inactive (dead)

6、修改配置文件，使该NTP服务器在不联网的情况下，使用本服务器的时间作为同步时间

vim /etc/ntp.conf

把如下四行代码注释掉

#server .centos.pool.ntp.org iburst
#server .centos.pool.ntp.org iburst
#server .centos.pool.ntp.org iburst
#server .centos.pool.ntp.org iburst

在下面再添加两行

server 127.127.1.0
fudge  127.127.1.0 stratum 

配置后：

[root@hadoop101 ~]# vim /etc/ntp.conf
# For more information about this file, see the man pages
# ntp.conf(), ntp_acc(), ntp_auth(), ntp_clock(), ntp_misc(), ntp_mon().

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 ::

# 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 127.127.1.0
fudge  127.127.1.0 stratum 0

#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   

# Specify the key identifier to use with the ntpdc utility.
#requestkey 

# Specify the key identifier to use with the ntpq utility.
#controlkey 

# Enable writing of statistics records.

7、启动ntp服务

systemctl start ntpd

或

service ntpd start

8、再次查看服务器状态是否配置成功

[root@hadoop101 mysql-libs]# systemctl status ntpd
● ntpd.service - Network Time Service
   Loaded: loaded (/usr/lib/systemd/system/ntpd.service; disabled; vendor preset: disabled)
   Active: active (running) since Fri -- :: CST; 13s ago
  Process:  ExecStart=/usr/sbin/ntpd -u ntp:ntp $OPTIONS (code=exited, status=/SUCCESS)
 Main PID:  (ntpd)
    Tasks:
   CGroup: /system.slice/ntpd.service
           └─ /usr/sbin/ntpd -u ntp:ntp -g

Aug  :: hadoop101.com ntpd[]: Listen normally on  ...
Aug  :: hadoop101.com ntpd[]: Listen normally on  ...
Aug  :: hadoop101.com ntpd[]: Listen normally on  ...
Aug  :: hadoop101.com ntpd[]: Listen normally on  ...
Aug  :: hadoop101.com ntpd[]: Listening on routing ...
Aug  :: hadoop101.com ntpd[]: 0.0.0.0 c016  restart
Aug  :: hadoop101.com ntpd[]: 0.0.0.0 c012  freq_...
Aug  :: hadoop101.com ntpd[]: 0.0.0.0 c011  freq_...
Aug  :: hadoop101.com systemd[]: Started Network Time ...
Aug  :: hadoop101.com ntpd[]: 0.0.0.0 c514  freq_...
Hint: Some lines were ellipsized, use -l to show in full.

或

[root@hadoop101 ~]# service ntpd status

9、查看是否同步

[root@hadoop101 ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
*LOCAL() .LOCL.  l    0.000 0.000 0.000

10、设置开机启动

[root@hadoop101 ~]# systemctl enable ntpd
Created symlink from /etc/systemd/system/multi-user.target.wants/ntpd.service to /usr/lib/systemd/system/ntpd.service.

11、设置防火墙，打开udp123端口（如果防火墙关了就不用设置了）

[root@hadoop101 ~]# firewall-cmd --permanent --add-port=/udp
success
[root@hadoop101 ~]# firewall-cmd --reload
success

12、查看防火墙已打开端口

iptables -L -n

二、客户端配置（其他节点）

前5步与服务器一致

6、修改配置文件，将刚刚搭建好的NTP服务器作为客户端上游时间服务器

vim /etc/ntp.conf
#注释掉其他上游时间服务器
#server .centos.pool.ntp.org iburst
#server .centos.pool.ntp.org iburst
#server .centos.pool.ntp.org iburst
#server .centos.pool.ntp.org iburst
#配置上游时间服务器为本地的ntpd Server服务器
server hadoop101.com
fudge hadoop101.com stratum 

#配置允许上游时间服务器主动修改本机的时间
restrict hadoop101.com nomodify notrap noquery

配置后：

[root@hadoop103 ~]# vi /etc/ntp.conf
# For more information about this file, see the man pages
# ntp.conf(), ntp_acc(), ntp_auth(), ntp_clock(), ntp_misc(), ntp_mon().

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

restrict hadoop101.com nomodify notrap noquery

# 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 hadoop101.com
fudge hadoop101.com stratum 0

#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   

# Specify the key identifier to use with the ntpdc utility.
#requestkey 

# Specify the key identifier to use with the ntpq utility.

7、与本地ntpd Server同步一下

[root@hadoop102 ~]# ntpdate -u hadoop101.com
 Aug :: ntpdate[]: adjust time server 192.168.1.101 offset 0.004621 sec

8、启动ntp服务

systemctl start ntpd

或

service ntpd start

9、设置开机启动

[root@hadoop102 ~]# systemctl enable ntpd
Created symlink from /etc/systemd/system/multi-user.target.wants/ntpd.service to /usr/lib/systemd/system/ntpd.service.

10、查看状态

[root@hadoop103 ~]# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 hadoop101.com   .LOCL.            u              8.148   -2.581   0.000

参考：https://blog.csdn.net/hellboy0621/article/details/81903091