VMWare掛起關機，又重啟后，出現一些很奇怪的問題。
我的幾臺CentOS的網卡都不見了，顯示網卡未被托管

[root@localhost ~]# nmcli device status
DEVICE      TYPE      STATE   CONNECTION 
virbr0      bridge    未托管  --         
ens33       ethernet  未托管  --         
lo          loopback  未托管  --         
virbr0-nic  tun       未托管  --         
[root@localhost ~]#   
[root@localhost ~]# nmcli connection up ens33
錯誤：連接激活失敗：No suitable device found for this connection (device lo not available because device is strictly unmanaged).

跟著AI，花了很多時間，嘗試了很多方法都不行，最后用下面的方法解決了

[root@localhost ldsinfo]# nmcli connection up ens33
錯誤：連接激活失敗：No suitable device found for this connection (device lo not available because device is strictly unmanaged).
[root@localhost ldsinfo]# 
[root@localhost ldsinfo]# 
[root@localhost ldsinfo]# 
[root@localhost ldsinfo]# 
[root@localhost ldsinfo]# sudo mv /etc/NetworkManager/NetworkManager.conf /etc/NetworkManager/NetworkManager.conf.bak
[root@localhost ldsinfo]# sudo mv /etc/sysconfig/network-scripts/ifcfg-ens33 /etc/sysconfig/network-scripts/ifcfg-ens33.bak
[root@localhost ldsinfo]# 
[root@localhost ldsinfo]# 
[root@localhost ldsinfo]# sudo tee /etc/NetworkManager/NetworkManager.conf <<'EOF'
> [main]
> plugins=ifcfg-rh
> [keyfile]
> unmanaged-devices=none
> EOF
[main]
plugins=ifcfg-rh
[keyfile]
unmanaged-devices=none
[root@localhost ldsinfo]# 
[root@localhost ldsinfo]# 
[root@localhost ldsinfo]# sudo tee /etc/sysconfig/network-scripts/ifcfg-ens33 <<'EOF'
> DEVICE=ens33
> TYPE=Ethernet
> BOOTPROTO=dhcp
> ONBOOT=yes
> NM_CONTROLLED=yes
> EOF
DEVICE=ens33
TYPE=Ethernet
BOOTPROTO=dhcp
ONBOOT=yes
NM_CONTROLLED=yes
[root@localhost ldsinfo]# 
[root@localhost ldsinfo]# 
[root@localhost ldsinfo]# sudo systemctl stop NetworkManager
[root@localhost ldsinfo]# sudo rm -rf /var/lib/NetworkManager/*
[root@localhost ldsinfo]# 
[root@localhost ldsinfo]# sudo systemctl restart NetworkManager
[root@localhost ldsinfo]# sudo nmcli device set ens33 managed yes
[root@localhost ldsinfo]# sudo nmcli connection add type ethernet ifname ens33 con-name ens33
連接 "ens33" (e4b6ba8b-70ff-42db-9c12-6726b892d0f5) 已成功添加。
[root@localhost ldsinfo]# sudo nmcli connection up ens33
連接已成功激活（D-Bus 活動路徑：/org/freedesktop/NetworkManager/ActiveConnection/3）
[root@localhost ldsinfo]# 
[root@localhost ldsinfo]# nmcli device status
DEVICE      TYPE      STATE   CONNECTION 
ens33       ethernet  已連接  ens33      
virbr0      bridge    已連接  virbr0     
lo          loopback  未托管  --         
virbr0-nic  tun       未托管  --         
[root@localhost ldsinfo]# 

終于顯示成功激活，“已連接”！

后來又測試了另外一臺，發現關鍵的點在于rm -rf /var/lib/NetworkManager/*，
將這里下面的文件刪除了，就解決，說明跟這個地方的配置有關！

然后再另一臺那里繼續探索，發現每次修改/var/lib/NetworkManager/
[main]
NetworkingEnabled=true
WirelessEnabled=true
WWANEnabled=true

重新啟動systemctl restart NetworkManager，
里面的值都被修改了，NetworkingEnabled=false
然后再運行nmcli networking查看狀態是disabled
全局開啟網絡：nmcli networking on
所有問題解決！

總結

過程中用到的命令

nmcli device status
systemctl stop NetworkManager
rm -rf /var/lib/NetworkManager/*
systemctl restart NetworkManager
nmcli device set ens33 managed yes
nmcli connection up ens33

nmcli networking
nmcli networking on

其實整個問題的解決可能就一條命令，就是nmcli networking on

IP地址配置文件參考：
/etc/sysconfig/network-scripts/ifcfg-ens33

TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=ens33
UUID=419a8fa8-cf1f-4ef1-886d-a6f8ae507ba9
DEVICE=ens33
ONBOOT=yes
IPV6_PRIVACY=no
DNS1=202.96.128.86
DNS2=114.114.114.114
DNS3=192.168.8.1
IPADDR=192.168.8.22
PREFIX=24
GATEWAY=192.168.8.1