CentOS7 Network Service开机无法启动的解决方法
CentOS7安装完成并配置好所有网络相关配置后重启机器，使用
$ systemctl --failed
检查是否有失败的服务
发现在network服务启动失败，使用systemctl status network查看服务状态，得到如下错误信息：
$ systemctl status network
Nov 23 22:09:07 hdcoe02 network[597]: Bringing up loopback interface: Could not load file '/etc/sysconfig/network-scripts/ifcfg-lo' Nov 23 22:09:07 hdcoe02 network[597]: Could not load file '/etc/sysconfig/network-scripts/ifcfg-lo' Nov 23 22:09:08 hdcoe02 network[597]: Could not load file '/etc/sysconfig/network-scripts/ifcfg-lo' Nov 23 22:09:08 hdcoe02 network[597]: Could not load file '/etc/sysconfig/network-scripts/ifcfg-lo' Nov 23 22:09:08 hdcoe02 network[597]: [ OK ] Nov 23 22:09:08 hdcoe02 network[597]: Bringing up interface enp0s25: Error: Connection activation failed: Connection 'enp0s25' is not available on the device enp0s25 at this time. Nov 23 22:09:08 hdcoe02 network[597]: [FAILED] Nov 23 22:09:08 hdcoe02 systemd[1]: network.service: control process exited, code=exited status=1 Nov 23 22:09:08 hdcoe02 systemd[1]: Failed to start LSB: Bring up/down networking.
设定开机启动一个名为NetworkManager-wait-online服务，命令为：
$ systemctl enable NetworkManager-wait-online.service
重启network:
$ systemctl restart network
