故障现象：

1.服务器无法被ping通

2.GUI界面右上角看不到网卡图标

正常情况GUI显示的网络图标：

Centos 9 网卡Network device is strictly unmanaged错误解决办法_network

故障时网络图标消失后的样子：

Centos 9 网卡Network device is strictly unmanaged错误解决办法_network_02

3.ip addr网卡没有地址

[root@xiamingliang ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens160: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 00:0c:29:c1:69:35 brd ff:ff:ff:ff:ff:ff
    altname enp3s0
3: br-1c57ae1d2940: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default 
    link/ether 02:42:3a:6b:40:d9 brd ff:ff:ff:ff:ff:ff
    inet 172.20.0.1/16 brd 172.20.255.255 scope global br-1c57ae1d2940
       valid_lft forever preferred_lft forever
……

3.nmcli device status状态为unmanaged

[root@xiamingliang ~]# nmcli device status 
DEVICE           TYPE      STATE      CONNECTION 
br-1c57ae1d2940  bridge    unmanaged  --         
br-37a032e957ba  bridge    unmanaged  --         
br-b365648bec89  bridge    unmanaged  --         
docker0          bridge    unmanaged  --         
ens160           ethernet  unmanaged  --         
veth5707956      ethernet  unmanaged  --         
vethfce698f      ethernet  unmanaged  --         
lo               loopback  unmanaged  --         
[root@OpenKM ~]#

4.nmcli connection show状态为unmanaged

[root@xiamingliang ~]# nmcli connection show 
NAME    UUID                                  TYPE      DEVICE 
ens160  cf32e4bc-eaf9-3db0-98bb-2879bd5153d8  ethernet  --     
[root@xiamingliang ~]#

5.尝试修复，出现device is strictly unmanaged报错

[root@xiamingliang ~]# nmcli connection up ens160 
Error: Connection activation failed: No suitable device found for this connection (device lo not available because device is strictly unmanaged).
[root@xiamingliang ~]#

[root@OpenKM ~]# nmcli device up ens160 
Error: Failed to add/activate new connection: Connection 'ens160' is not available on device ens160 because device is strictly unmanaged
[root@xiamingliang ~]#
[root@xiamingliang ~]# nmcli device set ens160 managed yes 
[root@xiamingliang ~]# nmcli device status 
DEVICE           TYPE      STATE      CONNECTION 
br-1c57ae1d2940  bridge    unmanaged  --         
br-37a032e957ba  bridge    unmanaged  --         
br-b365648bec89  bridge    unmanaged  --         
docker0          bridge    unmanaged  --         
ens160           ethernet  unmanaged  --         
veth1ea0122      ethernet  unmanaged  --         
veth5707956      ethernet  unmanaged  --         
lo               loopback  unmanaged  --         
[root@OpenKM ~]#

尝试restart和reload NetworkManager.service均无效

[root@xiamingliang ~]# systemctl reload NetworkManager.service 
[root@xiamingliang ~]# nmcli device status 
DEVICE           TYPE      STATE      CONNECTION 
br-1c57ae1d2940  bridge    unmanaged  --         
br-37a032e957ba  bridge    unmanaged  --         
br-b365648bec89  bridge    unmanaged  --         
docker0          bridge    unmanaged  --         
ens160           ethernet  unmanaged  --         
veth5707956      ethernet  unmanaged  --         
veth6817ed8      ethernet  unmanaged  --         
lo               loopback  unmanaged  --         
[root@xiamingliang ~]#

解决办法：

我的环境解决办法是：

//确定NetworkManager是否已接管了系统的网络连接管理
[root@xiamingliang ~]# nmcli networking 
disabled
[root@xiamingliang ~]#

//若没有解决则需要手动开启接管
[root@xiamingliang ~]# nmcli networking on
[root@xiamingliang ~]# 

//接管后恢复正常
[root@xiamingliang ~]# nmcli connection show 
NAME    UUID                                  TYPE      DEVICE 
ens160  cf32e4bc-eaf9-3db0-98bb-2879bd5153d8  ethernet  ens160 
[root@xiamingliang ~]# nmcli device status 
DEVICE           TYPE      STATE                   CONNECTION 
ens160           ethernet  connected               ens160     
docker0          bridge    connected (externally)  docker0    
br-1c57ae1d2940  bridge    disconnected            --         
br-37a032e957ba  bridge    disconnected            --         
br-b365648bec89  bridge    disconnected            --         
veth5707956      ethernet  unmanaged               --         
veth6df1eb1      ethernet  unmanaged               --         
lo               loopback  unmanaged               --         
[root@xiamingliang ~]#

可能的其他解决方法：

或者也可以修改NetworkManager.service配置文件后再重启服务解决；配置文件路径是：/var/lib/NetworkManager/NetworkManager.state

[root@xiamingliang ~]# cat /var/lib/NetworkManager/NetworkManager.state
[main]
NetworkingEnabled=true
WirelessEnabled=true
WWANEnabled=true
[root@xiamingliang ~]#

注意：操作顺序先stop服务，再修改配置文件；最后启动服务。

[root@xiamingliang ~]# systemctl stop NetworkManager
[root@xiamingliang ~]# vi /var/lib/NetworkManager/NetworkManager.state
[root@xiamingliang ~]# cat /var/lib/NetworkManager/NetworkManager.state
[main]
NetworkingEnabled=true      //修改为true
WirelessEnabled=true
WWANEnabled=true
[root@xiamingliang ~]# systemctl start NetworkManager
[root@xiamingliang ~]#

故障原因：

未知系统原因导致NetworkManager没有正确接管系统的网络连接管理；其实，没有调整过NetworkManager配置的情况下重启服务器也是可以解决的，但是极端情况下要避免服务器的重启操作，这个方法会很有效。



本文一来分享一些技术问题的解决方法；二来也作为自己的经历记录；希望可以帮到更多有需要的人。