关于linux搭建ntp时间同步服务

[root@node1 ~]# rpm -qa | grep ntp
fontpackages-filesystem-1.44-8.el7.noarch
ntp-4.2.6p5-29.el7.centos.2.x86_64
ntpdate-4.2.6p5-29.el7.centos.2.x86_64

[root@node1 ~] vim /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
# nomodify允许局域网客户端同步

# 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
#将以上默认时间源都注释

#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

server ntp1.aliyun.com
server time.nist.gov
#在最后加入以上两行时间源

[root@node1 ~]# crontab -e

[root@node1 ~]# systemctl start ntpd     
[root@node1 ~]# systemctl status ntpd

[root@node1 ~]# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+120.25.115.20   10.137.53.7      2 u   74   64  176   44.800   11.154   4.838
*time-a-b.nist.g .NIST.           1 u    8   64  377  199.241   -5.427   3.776

[root@node1 ~]# ntpstat 
synchronised to NTP server (132.163.96.1) at stratum 2
   time correct to within 176 ms
   polling server every 64 s

[root@node2 ~]# rpm -qa | grep ntpdate        
ntpdate-4.2.6p5-29.el7.centos.2.x86_64

[root@node2 ~]# ntpdate 192.168.149.20     
22 Apr 11:06:29 ntpdate[1806]: no server suitable for synchronization found

[root@node2 ~]# ntpdate 192.168.149.20
22 Apr 11:09:22 ntpdate[1854]: adjust time server 192.168.149.20 offset -0.017823 sec