解决CentOS 7 开机网络设备不启动方法

在VMware 10里新装一个CentOS 7系统，开机发现没有网络，于是ifconfig一下发现网卡没有启动

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

ether 00:0c:29:2b:c0:1e txqueuelen 1000 (Ethernet)

RX packets 1 bytes 251 (251.0 B)

RX errors 0 dropped 0 overruns 0 frame 0

TX packets 0 bytes 0 (0.0 B)

TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536

inet 127.0.0.1 netmask 255.0.0.0

inet6 ::1 prefixlen 128 scopeid 0x10<host>

loop txqueuelen 0 (Local Loopback)

RX packets 386 bytes 33512 (32.7 KiB)

RX errors 0 dropped 0 overruns 0 frame 0

TX packets 386 bytes 33512 (32.7 KiB)

TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

习惯性的重启网卡服务“service network restart”

提示：

Restarting network (via systemctl): [ OK ]

重启OK，，，，

再查看网卡"ifconfig"

还是老样子

于是"ifup eno16777736"手动重启网卡

提示：

Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/0)

启动成功

再查看网卡状态"ifconfig"

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

inet 192.168.41.128 netmask 255.255.255.0 broadcast 192.168.41.255

inet6 fe80::20c:29ff:fe2b:c01e prefixlen 64 scopeid 0x20<link>

ether 00:0c:29:2b:c0:1e txqueuelen 1000 (Ethernet)

RX packets 74 bytes 9637 (9.4 KiB)

RX errors 0 dropped 0 overruns 0 frame 0

TX packets 61 bytes 7083 (6.9 KiB)

TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536

inet 127.0.0.1 netmask 255.0.0.0

inet6 ::1 prefixlen 128 scopeid 0x10<host>

loop txqueuelen 0 (Local Loopback)

RX packets 650 bytes 56612 (55.2 KiB)

RX errors 0 dropped 0 overruns 0 frame 0

TX packets 650 bytes 56612 (55.2 KiB)

TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

OK，，得到IP问题解决，，

后续：

本来这个问题不会出现的，主要是我的网络环境是有DHCP服务器，IP地址可以自动获得。如果是手动输入IP就不会出现这个问题了，因为在网卡配置文件里有一项"ONBOOT=no"表示引导时不激活网卡，由于对centos7不熟悉，所以未发现这个问题。

上面的解决方法是不彻底的，因为每重启一次服务器就需要输入一次"ifup eno16777736",很是麻烦，我们可以修改网卡的配置文件"/etc/sysconfig/network-scripts/ifcfg-eno16777736"里面的"ONBOOT=no"修改成"ONBOOT=yes",至此问题彻底解决！