原文地址：http://addam.blog.51cto.com/5041993/1839518

刚刚装好的虚拟机突然不能上网了，报错很诡异，具体报错如下：

/etc/init.d/network restart

Restarting network (via systemctl):  Job for network.service failed because the control process exited with error code. See "systemctl status network.service" and "journalctl -xe" for details.

[失败]

使用systemctl status network.service命令查看结果如下：

network.service - LSB: Bring up/down networking

Loaded: loaded (/etc/rc.d/init.d/network)

Active: failed (Result: exit-code) since 三 2016-08-17 11:34:36 CST; 54s ago

Docs: man:systemd-sysv-generator(8)

Process: 3847 ExecStart=/etc/rc.d/init.d/network start (code=exited, status=1/FAILURE)

8月 17 11:34:36 python.cn network[3847]: RTNETLINK answers: File exists

8月 17 11:34:36 python.cn network[3847]: RTNETLINK answers: File exists

8月 17 11:34:36 python.cn network[3847]: RTNETLINK answers: File exists

8月 17 11:34:36 python.cn network[3847]: RTNETLINK answers: File exists

8月 17 11:34:36 python.cn network[3847]: RTNETLINK answers: File exists

8月 17 11:34:36 python.cn network[3847]: RTNETLINK answers: File exists

8月 17 11:34:36 python.cn systemd[1]: network.service: control process exited, code=exited status=1

8月 17 11:34:36 python.cn systemd[1]: Failed to start LSB: Bring up/down networking.

8月 17 11:34:36 python.cn systemd[1]: Unit network.service entered failed state.

8月 17 11:34:36 python.cn systemd[1]: network.service failed.

查看系统日志，报错如下：

Aug 17 11:34:36 python network: RTNETLINK answers: File exists

Aug 17 11:34:36 python network: RTNETLINK answers: File exists

Aug 17 11:34:36 python network: RTNETLINK answers: File exists

Aug 17 11:34:36 python network: RTNETLINK answers: File exists

Aug 17 11:34:36 python network: RTNETLINK answers: File exists

Aug 17 11:34:36 python network: RTNETLINK answers: File exists

Aug 17 11:34:36 python network: RTNETLINK answers: File exists

Aug 17 11:34:36 python network: RTNETLINK answers: File exists

Aug 17 11:34:36 python network: RTNETLINK answers: File exists

Aug 17 11:34:36 python systemd: network.service: control process exited, code=exited status=1

Aug 17 11:34:36 python systemd: Failed to start LSB: Bring up/down networking.

Aug 17 11:34:36 python systemd: Unit network.service entered failed state.

Aug 17 11:34:36 python systemd: network.service failed.

Aug 17 11:36:28 python systemd: Starting LSB: Bring up/down networking...

Aug 17 11:36:29 python network: 正在打开环回接口： 无法载入文件 ‘/etc/sysconfig/network-scripts/ifcfg-lo‘

Aug 17 11:36:29 python network: 无法载入文件 ‘/etc/sysconfig/network-scripts/ifcfg-lo‘

Aug 17 11:36:29 python network: 无法载入文件 ‘/etc/sysconfig/network-scripts/ifcfg-lo‘

Aug 17 11:36:29 python network: 无法载入文件 ‘/etc/sysconfig/network-scripts/ifcfg-lo‘

Aug 17 11:36:29 python network: [  确定  ]

Aug 17 11:36:29 python network: 正在打开接口 eno16777736： 错误：激活连接失败：No suitable device found for this connection.

经查，确认/etc/sysconfig/network-scripts/ifcfg-lo文件是存在的。问题出现在哪里呢？无法，只好百度一下吧，百度出来的结果竟然基本一样。

百度答案：

mac地址不对，修改mac地址。

也许有人确实是mac问题，但是莫名其妙怎么可能mac地址更改了，除非你添加新网卡或者克隆的虚拟机。

我特么真笑了，天下百度文章一大抄啊。。。。。。。。

没办法了，Google一下吧，偶然看到一个文章，大意是跟系统自带的NetworkManager这个管理套件有关系，关掉就可以解决。

试一下：

systemctl stop NetworkManager

systemctl disable NetworkManager

Removed symlink /etc/systemd/system/multi-user.target.wants/NetworkManager.service.

Removed symlink /etc/systemd/system/dbus-org.freedesktop.NetworkManager.service.

Removed symlink /etc/systemd/system/dbus-org.freedesktop.nm-dispatcher.service.

重新启动网络：

systemctl start network.service

ifconfig |grep eno

eno16777736: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500

inet 192.168.1.192  netmask 255.255.255.0  broadcast 192.168.1.255

inet6 fe80::20c:29ff:fe3d:b305  prefixlen 64  scopeid 0x20<link>

ether 00:0c:29:3d:b3:05  txqueuelen 1000  (Ethernet)

RX packets 2  bytes 120 (120.0 B)

RX errors 0  dropped 0  overruns 0  frame 0

TX packets 22  bytes 3551 (3.4 KiB)

TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

网络正常启动，访问正常。

CentOS7 Failed to start LSB: Bring up/down