Implementation of CentOS8.0 network configuration

1. Differences in network configuration between CentOS 7 and CentOS 8:

CentOS 8.0.1905 is installed in VMware Workstation 15 Pro, but when configuring the IP address, it is found that the network.service is missing and there are no script files in the /etc/sysconfig/network-scripts directory. CentOS 7 supports both network.service and NetworkManager.service (NM for short) to configure the network, while in CentOS 8, network.service has been abandoned and the network must be configured through NetworkManager.service.

2. Simple instructions for using the NetworkManager command line tool nmcli:

1. Check IP (similar to ifconfig, ip a): # nmcli

2. Three ways to activate the network card (equivalent to ifup):

(1)# nmcli c up ens33

Note: nmcli c | connection, connection, can be understood as a configuration file, equivalent to ifcfg-ethX or ifcfg-ensX

(2)# nmcli d connect ens33

Note: nmcli d | device, device, can be understood as the actual network card (including physical network card and virtual network card)

(3)# nmcli d reapply ens33

3. Disable the network card (equivalent to ifdown): # nmcli c down ens33

4. View the connection list: # nmcli c show

5. View connection details: # nmcli c show ens33

6. Reload all ifcfg or route to connection (will not take effect immediately): # nmcli c reload

7. View the device list: # nmcli d

Note: device has 4 states

(1) connected: managed by the NM and currently has an active connection

(2) disconnected: managed by NM, but currently has no active connection

(3) unmanaged: not managed by NM

(4) unavailable: unavailable, NM cannot manage, usually occurs when the network card link is down (such as: ip link set ethX down)

8. View all device details: # nmcli d show

9. View the detailed information of the specified device: # nmcli d show ens33

10. Check the NM management status: # nmcli n

11. Enable NM management: # nmcli n on

12. Check whether NM is available online: # nm-online

Note: For detailed instructions on the use of the nmcli command, refer to # man nmcli or # nmcli -h . For the usage of specific objects such as device , refer to # man nmcli d or # nmcli d -h.

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