PHP_network_getaddresses：getaddrinfo失败：名称或服务未知

此消息似乎与网络/ DNS相关.服务器日志清楚地表明,在第一次发生错误的时候,Ubuntu启动了无人值守升级会话.我将附加下面的dpkg.log的输出.

我们使用外部数据库服务器.

我们决定重新启动网络服务器,这解决了这个问题,但现在的问题是：

有什么方法可以找出这个问题的根本原因,以便将来可以阻止它吗？

unattended-upgrades.log的输出：

2017-03-21 15:01:56,279 INFO Starting unattended upgrades script
2017-03-21 15:01:56,279 INFO Allowed origins are: ['o=Ubuntu,a=xenial','o=Ubuntu,a=xenial-security']
2017-03-21 15:02:03,365 INFO Packages that will be upgraded: libc-bin libc-dev-bin libc6 libc6-dev libfreetype6 locales multiarch-support
2017-03-21 15:02:03,365 INFO Writing dpkg log to '/var/log/unattended-upgrades/unattended-upgrades-dpkg.log'
2017-03-21 15:02:12,851 INFO All upgrades installed

dpkg.log的输出：

2017-03-21 15:02:03 startup archives unpack
2017-03-21 15:02:03 upgrade libc6-dev:amd64 2.23-0ubuntu5 2.23-0ubuntu6
2017-03-21 15:02:03 status half-configured libc6-dev:amd64 2.23-0ubuntu5
2017-03-21 15:02:03 status unpacked libc6-dev:amd64 2.23-0ubuntu5
2017-03-21 15:02:03 status half-installed libc6-dev:amd64 2.23-0ubuntu5
2017-03-21 15:02:04 status half-installed libc6-dev:amd64 2.23-0ubuntu5
2017-03-21 15:02:04 status unpacked libc6-dev:amd64 2.23-0ubuntu6
2017-03-21 15:02:04 status unpacked libc6-dev:amd64 2.23-0ubuntu6
2017-03-21 15:02:04 upgrade libc-dev-bin:amd64 2.23-0ubuntu5 2.23-0ubuntu6
2017-03-21 15:02:04 status half-configured libc-dev-bin:amd64 2.23-0ubuntu5
2017-03-21 15:02:04 status unpacked libc-dev-bin:amd64 2.23-0ubuntu5
2017-03-21 15:02:04 status half-installed libc-dev-bin:amd64 2.23-0ubuntu5
2017-03-21 15:02:04 status triggers-pending man-db:amd64 2.7.5-1
2017-03-21 15:02:04 status half-installed libc-dev-bin:amd64 2.23-0ubuntu5
2017-03-21 15:02:04 status unpacked libc-dev-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:04 status unpacked libc-dev-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:04 upgrade libc6:amd64 2.23-0ubuntu5 2.23-0ubuntu6
2017-03-21 15:02:04 status triggers-pending libc-bin:amd64 2.23-0ubuntu5
2017-03-21 15:02:04 status half-configured libc6:amd64 2.23-0ubuntu5
2017-03-21 15:02:04 status unpacked libc6:amd64 2.23-0ubuntu5
2017-03-21 15:02:04 status half-installed libc6:amd64 2.23-0ubuntu5
2017-03-21 15:02:05 status half-installed libc6:amd64 2.23-0ubuntu5
2017-03-21 15:02:05 status unpacked libc6:amd64 2.23-0ubuntu6
2017-03-21 15:02:05 status unpacked libc6:amd64 2.23-0ubuntu6
2017-03-21 15:02:05 startup packages configure
2017-03-21 15:02:05 configure libc6:amd64 2.23-0ubuntu6 <none>
2017-03-21 15:02:05 status unpacked libc6:amd64 2.23-0ubuntu6
2017-03-21 15:02:05 status unpacked libc6:amd64 2.23-0ubuntu6
2017-03-21 15:02:05 status half-configured libc6:amd64 2.23-0ubuntu6
2017-03-21 15:02:05 status installed libc6:amd64 2.23-0ubuntu6
2017-03-21 15:02:05 trigproc libc-bin:amd64 2.23-0ubuntu5 <none>
2017-03-21 15:02:05 status half-configured libc-bin:amd64 2.23-0ubuntu5
2017-03-21 15:02:05 status installed libc-bin:amd64 2.23-0ubuntu5
2017-03-21 15:02:05 trigproc man-db:amd64 2.7.5-1 <none>
2017-03-21 15:02:05 status half-configured man-db:amd64 2.7.5-1
2017-03-21 15:02:05 status installed man-db:amd64 2.7.5-1
2017-03-21 15:02:05 startup archives unpack
2017-03-21 15:02:05 upgrade locales:all 2.23-0ubuntu5 2.23-0ubuntu6
2017-03-21 15:02:05 status half-configured locales:all 2.23-0ubuntu5
2017-03-21 15:02:05 status unpacked locales:all 2.23-0ubuntu5
2017-03-21 15:02:05 status half-installed locales:all 2.23-0ubuntu5
2017-03-21 15:02:06 status triggers-pending man-db:amd64 2.7.5-1
2017-03-21 15:02:06 status half-installed locales:all 2.23-0ubuntu5
2017-03-21 15:02:06 status unpacked locales:all 2.23-0ubuntu6
2017-03-21 15:02:06 status unpacked locales:all 2.23-0ubuntu6
2017-03-21 15:02:06 upgrade libc-bin:amd64 2.23-0ubuntu5 2.23-0ubuntu6
2017-03-21 15:02:06 status half-configured libc-bin:amd64 2.23-0ubuntu5
2017-03-21 15:02:06 status unpacked libc-bin:amd64 2.23-0ubuntu5
2017-03-21 15:02:06 status half-installed libc-bin:amd64 2.23-0ubuntu5
2017-03-21 15:02:06 status half-installed libc-bin:amd64 2.23-0ubuntu5
2017-03-21 15:02:06 status unpacked libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:06 status unpacked libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:06 trigproc man-db:amd64 2.7.5-1 <none>
2017-03-21 15:02:06 status half-configured man-db:amd64 2.7.5-1
2017-03-21 15:02:07 status installed man-db:amd64 2.7.5-1
2017-03-21 15:02:07 startup packages configure
2017-03-21 15:02:07 configure libc-bin:amd64 2.23-0ubuntu6 <none>
2017-03-21 15:02:07 status unpacked libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status unpacked libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status unpacked libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status unpacked libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status unpacked libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status unpacked libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status half-configured libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status installed libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 startup archives unpack
2017-03-21 15:02:07 upgrade multiarch-support:amd64 2.23-0ubuntu5 2.23-0ubuntu6
2017-03-21 15:02:07 status half-configured multiarch-support:amd64 2.23-0ubuntu5
2017-03-21 15:02:07 status unpacked multiarch-support:amd64 2.23-0ubuntu5
2017-03-21 15:02:07 status half-installed multiarch-support:amd64 2.23-0ubuntu5
2017-03-21 15:02:07 status half-installed multiarch-support:amd64 2.23-0ubuntu5
2017-03-21 15:02:07 status unpacked multiarch-support:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status unpacked multiarch-support:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 startup packages configure
2017-03-21 15:02:07 configure multiarch-support:amd64 2.23-0ubuntu6 <none>
2017-03-21 15:02:07 status unpacked multiarch-support:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status half-configured multiarch-support:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status installed multiarch-support:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 startup archives unpack
2017-03-21 15:02:07 upgrade libfreetype6:amd64 2.6.1-0.1ubuntu2 2.6.1-0.1ubuntu2.1
2017-03-21 15:02:07 status triggers-pending libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status half-configured libfreetype6:amd64 2.6.1-0.1ubuntu2
2017-03-21 15:02:07 status unpacked libfreetype6:amd64 2.6.1-0.1ubuntu2
2017-03-21 15:02:07 status half-installed libfreetype6:amd64 2.6.1-0.1ubuntu2
2017-03-21 15:02:07 status half-installed libfreetype6:amd64 2.6.1-0.1ubuntu2
2017-03-21 15:02:07 status unpacked libfreetype6:amd64 2.6.1-0.1ubuntu2.1
2017-03-21 15:02:07 status unpacked libfreetype6:amd64 2.6.1-0.1ubuntu2.1
2017-03-21 15:02:07 trigproc libc-bin:amd64 2.23-0ubuntu6 <none>
2017-03-21 15:02:07 status half-configured libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status installed libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 startup packages configure
2017-03-21 15:02:07 configure libc-dev-bin:amd64 2.23-0ubuntu6 <none>
2017-03-21 15:02:07 status unpacked libc-dev-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status half-configured libc-dev-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status installed libc-dev-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 configure libc6-dev:amd64 2.23-0ubuntu6 <none>
2017-03-21 15:02:07 status unpacked libc6-dev:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status half-configured libc6-dev:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 status installed libc6-dev:amd64 2.23-0ubuntu6
2017-03-21 15:02:07 configure locales:all 2.23-0ubuntu6 <none>
2017-03-21 15:02:07 status unpacked locales:all 2.23-0ubuntu6
2017-03-21 15:02:07 status unpacked locales:all 2.23-0ubuntu6
2017-03-21 15:02:07 status half-configured locales:all 2.23-0ubuntu6
2017-03-21 15:02:11 status installed locales:all 2.23-0ubuntu6
2017-03-21 15:02:11 configure libfreetype6:amd64 2.6.1-0.1ubuntu2.1 <none>
2017-03-21 15:02:11 status triggers-pending libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:11 status unpacked libfreetype6:amd64 2.6.1-0.1ubuntu2.1
2017-03-21 15:02:11 status half-configured libfreetype6:amd64 2.6.1-0.1ubuntu2.1
2017-03-21 15:02:11 status installed libfreetype6:amd64 2.6.1-0.1ubuntu2.1
2017-03-21 15:02:11 trigproc libc-bin:amd64 2.23-0ubuntu6 <none>
2017-03-21 15:02:11 status half-configured libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:11 status installed libc-bin:amd64 2.23-0ubuntu6
2017-03-21 15:02:11 startup packages configure