1、问题描述
CentOS 8重启后网卡不见了，也无法上网。
2、尝试用nmcli connection up ens160命令修复，提示 unmanaged
root@compute02 network-scripts# nmcli connection up ens160
Error: Connection activation failed: No suitable device found for this connection (device lo not available because device is strictly unmanaged).
3、通过nmcli device status 命令查询了一下设备状态，为unmanaged
root@compute02 network-scripts# nmcli device status
DEVICE TYPE STATE CONNECTION
virbr0 bridge unmanaged --
ens160 ethernet unmanaged --
ens192 ethernet unmanaged --
lo loopback unmanaged --
4、确定NetworkManager是否已接管了系统的网络连接管理，发现是disabled
root@compute02 network-scripts# nmcli networking
disabled
5、手动开启，问题解决
root@compute02 network-scripts# nmcli networking on
root@compute02 network-scripts# ping www.baidu.com
PING www.a.shifen.com (14.119.104.254) 56(84) bytes of data.
64 bytes from 14.119.104.254 (14.119.104.254): icmp_seq=1 ttl=50 time=20.8 ms
64 bytes from 14.119.104.254 (14.119.104.254): icmp_seq=2 ttl=50 time=20.2 ms
64 bytes from 14.119.104.254 (14.119.104.254): icmp_seq=3 ttl=50 time=19.9 ms
64 bytes from 14.119.104.254 (14.119.104.254): icmp_seq=4 ttl=50 time=20.0 ms