CentOS 7中的NTP同步

Question

我在CentOS 7机器(虚拟机器)上配置了NTP服务器，并配置了客户端的ntp.conf文件(也是虚拟的并运行CentOS 7)。当我在客户机上使用"systemctl (re)start ntpd“显式启动/重新启动ntpd服务时，NTP同步工作得很好。但是，当我试图通过更改服务器上的时间来测试“自动”同步时，客户端既不会收到“通知”，也不会更新他们的时钟(时钟在ntpd上一次重新启动时保持同步)。我甚至试图从客户端的ntp.conf文件中更改轮询频率，但似乎没有什么效果。我真的很感谢你的帮助。

PS:以下是来自服务器和一个客户端的ntp.conf文件：

服务器：

# 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 127.127.1.0

fudge 127.127.1.0 stratum 1

#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

客户端：

# 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 192.168.1.38 #This is the ip address of the server

#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

Answer 1

我认为您还必须取消对服务器上的restrict行的注释，以使ntp在该网络中可用。然后重新启动ntpd。

restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap

在客户端，还可以将iburst添加到服务器配置行，这将加快初始时钟同步并重新启动ntpd。

server 192.168.1.38 iburst

使用ntpq -p，您可以列出服务器以及是否建立了连接。

Answer 2

关于您的配置的几个注意事项：

我使用的一个一般规则是：

• 不要将ntp服务器放在虚拟机上
• 不要信任ntp服务器上的本地时钟。

您将使用隔离网络(因此无法联系到池服务器)。你可能得依赖硬件时钟了。但是尝试将ntp服务器从VM中取出。

对于客户端，在VM中，我总是在ntp.conf中作为第一行：

tinker panic 0

这样，当有一个大的时间偏移时，NTP就不会恐慌。

Answer 3

在(Re)启动期间，您可能没有与ntpd同步，但是通过使用ntpdate (您可以检查/etc/sysconfig/ntpdate是否存在)。

此外，他的客户可能对自己的时钟有一些信任，不会做出任何突然的跳跃。ntpd，如果在主时钟中遇到突然的变化(也就是那些对你来说很明显的变化)，就会假设主时钟有故障，并继续自己的时间。

由于你没有解释你为什么要这么做，所以如果你不必这样做的话，除了不要和ntp玩以外，很难给出建议。

您还应该反复检查chronyd和/或systemd的时间同步不干扰您的实验。