Let's say you have one or more network interfaces in your /etc/sysconfig/network-scripts directory. In this example there is a local host network interface (ifcfg-lo) and an ethernet network interface (ifcfg-eth0).

~]# ll /etc/sysconfig/network-scripts
total 224
-rw-r--r--. 1 root root   304 Oct  8  2020 ifcfg-eth0
-rw-r--r--. 1 root root   254 Aug 10  2022 ifcfg-lo

apt-get, dnf or yum can be used to install the NetworkManager package.

dnf install NetworkManager

And then start and enable NetworkManager.

systemctl start NetworkManager
systemctl enable NetworkManager

Then the nmcli connection migrate command can be used to migrate each ethernet network script to Network Manager.

~]# nmcli connection migrate eth0
Connection 'eth0' (5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03) successfully migrated.

There should now no longer be an ifcfg-eth0 file in the /etc/sysconfig/network-scripts directory in this example.

~]# ll /etc/sysconfig/network-scripts
total 224

-rw-r--r--. 1 root root   254 Aug 10  2022 ifcfg-lo

And the nmcli connection command should show that the eth0 interface is now being managed by Network Manager.

~]# nmcli connection
NAME  UUID                                  TYPE      DEVICE
eth0  5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03  ethernet  eth0