之前裝好的虛擬機突然不能上網了，具體報錯如下：
systemctl 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.
[失敗]
使用systemctl status network.service命令查看結果如下：
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.
查看系統日志more /var/log/messages |grep network，報錯如下：
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: 正在打開環回接口： 無法載入文件 '/etc/sysconfig/network-scripts/ifcfg-lo'
Aug 17 11:36:29 python network: 無法載入文件 '/etc/sysconfig/network-scripts/ifcfg-lo'
Aug 17 11:36:29 python network: 無法載入文件 '/etc/sysconfig/network-scripts/ifcfg-lo'
Aug 17 11:36:29 python network: 無法載入文件 '/etc/sysconfig/network-scripts/ifcfg-lo'
Aug 17 11:36:29 python network: [ 確定 ]
Aug 17 11:36:29 python network: 正在打開接口 eno16777736： 錯誤：激活連接失敗：No suitable device found for this connection.
經查，確認/etc/sysconfig/network-scripts/ifcfg-lo文件是存在的。
百度答案：
mac地址不對，修改mac地址。
編輯文件，加入mac地址。
vi /etc/sysconfig/network-scripts/ifcfg-eno16777736
HWADDR=
Google答案，跟系統自帶的NetworkManager這個管理套件有關系，關掉就可以解決。
systemctl stop NetworkManager
systemctl disable NetworkManager
重新啟動網絡：
systemctl start network.service
或重啟reboot，再次查看網絡systemctl status network。
網絡正常啟動，訪問正常。