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为什么NTP服务会成功退出？

tag-icon • tag-icon virtual-machines hyper-v systemd ntp ntpd
为什么NTP服务会成功退出？

我在运行 Windows 8 Hyper-V 的虚拟 Debian 8 机器上反复遇到日期时间停滞的问题。我没有做太多的安装后配置，这是一个刻意的相当普通的安装，没有什么花哨的东西——我只是把这个盒子当作一个独立的 POSIX 环境，通过 SSH 使用 PuTTY 登录。

当主机休眠时，日期似乎“冻结”，大约一天后，我打开主机笔记本电脑的盖子将其唤醒。Windows 上 PuTTy 与虚拟机的 SSH 会话始终保持完整。我不想为 Linux 的 Hyper-V 特定时间同步服务而烦恼，我满足于使用 NTP。NTP 已安装，apt-get install ntp最初我使用 获得以下信息systemctl status ntp：

● ntp.service - LSB: Start NTP daemon
   Loaded: loaded (/etc/init.d/ntp)
   Active: active (running) since Mon 2017-08-14 23:16:55 CEST; 20h ago
  Process: 1167 ExecStop=/etc/init.d/ntp stop (code=exited, status=0/SUCCESS)
  Process: 1175 ExecStart=/etc/init.d/ntp start (code=exited, status=0/SUCCESS)
   CGroup: /system.slice/ntp.service
           └─1184 /usr/sbin/ntpd -p /var/run/ntpd.pid -g -u 108:115

今天唤醒笔记本电脑并再次观察昨天的“冻结”日期后，与上述相同的命令告诉我服务已退出：

● ntp.service - LSB: Start NTP daemon
   Loaded: loaded (/etc/init.d/ntp)
   Active: active (exited) since Mon 2017-08-14 21:28:57 CEST; 1h 43min ago
  Process: 450 ExecStart=/etc/init.d/ntp start (code=exited, status=0/SUCCESS)

为什么服务似乎会自动退出？显然，只要主机从睡眠/休眠状态解冻，它就会退出。而且0/SUCCESS，为什么让我相信它的行为是按照设计进行的，并且不会遇到错误？

一旦我systemctl restart ntp将该进程重新归入计划进程中并且日期已同步。执行systemctl start ntp不会产生相同的效果（可能是因为它已经“加载”/“活动”）。

发生了什么事？NTP 不是应该一直运行，并在时钟漂移时根据需要定期同步时钟吗？这是内核中与 Hyper-V 相关的一些模块，它是否采纳了 Microsoft 的建议，即不要将 NTP 与虚拟机一起使用，或者可能是网络堆栈导致 NTP 失效？即使它是 UDP，甚至虚拟机的 SSH 仍然存在，那么这为什么会成为问题呢？

/etc/ntp.conf，我自己从来没有编辑过它：

# /etc/ntp.conf, configuration for ntpd; see ntp.conf(6) for help

driftfile /var/lib/ntp/ntp.drift


# Enable this if you want statistics to be logged.
#statsdir /var/log/ntpstats/

statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable


# You do need to talk to an NTP server or two (or three).
#server ntp.your-provider.example

# pool.ntp.org maps to about 1000 low-stratum NTP servers.  Your server will
# pick a different set every time it starts up.  Please consider joining the
# pool: <http://www.pool.ntp.org/join.html>
server 0.debian.pool.ntp.org iburst
server 1.debian.pool.ntp.org iburst
server 2.debian.pool.ntp.org iburst
server 3.debian.pool.ntp.org iburst


# Access control configuration; see /usr/share/doc/ntp-doc/html/accopt.html for
# details.  The web page <http://support.ntp.org/bin/view/Support/AccessRestrictions>
# might also be helpful.
#
# Note that "restrict" applies to both servers and clients, so a configuration
# that might be intended to block requests from certain clients could also end
# up blocking replies from your own upstream servers.

# By default, exchange time with everybody, but don't allow configuration.
restrict -4 default kod notrap nomodify nopeer noquery
restrict -6 default kod notrap nomodify nopeer noquery

# Local users may interrogate the ntp server more closely.
restrict 127.0.0.1
restrict ::1

# Clients from this (example!) subnet have unlimited access, but only if
# cryptographically authenticated.
#restrict 192.168.123.0 mask 255.255.255.0 notrust


# If you want to provide time to your local subnet, change the next line.
# (Again, the address is an example only.)
#broadcast 192.168.123.255

# If you want to listen to time broadcasts on your local subnet, de-comment the
# next lines.  Please do this only if you trust everybody on the network!
#disable auth
#broadcastclient

答案1

默认情况下，ntpd如果系统时间与其计算的时间相差太远，它将退出。（我不确定它将使用什么退出代码。）您可以添加配置指令tinker panic 0来阻止它退出。

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