RHEL7/CentOS7 Network Service开机无法启动的解决方法

RHEL7/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：

<span style="font-family:Microsoft YaHei;font-size:14px;"># systemctl status network
network.service - LSB: Bring up/down networking
   Loaded: loaded (/etc/rc.d/init.d/network)
   Active: failed (Result: exit-code) since Sun 2014-11-23 22:09:08 EST; 15min ago
  Process: 597 ExecStart=/etc/rc.d/init.d/network start (code=exited, status=1/FAILURE)

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.
Nov 23 22:09:08 hdcoe02 systemd[1]: Unit network.service entered failed state.</span>

通过查找相关文档，使用如下方法解决了问题：设定开机启动一个名为NetworkManager-wait-online服务，命令为：

systemctl enable NetworkManager-wait-online.service