Among other things, Systemd also handles the network and network-online target units.
The Target units define different states of the operating system, for example, we have the graphical target, the multi user target, ...
The "NetworkManager-wait-online.service" waits for a period of time for the networking to be set up before starting, it has the below parameters:
The networkonline.target waits until the network is connected.
To make sure a the network is available before a service is started, we change the below parameters:
We edit the service as below:
And we add the below parameter under the [Unit] section:
Linux puts systemd service files in the "/usr/lib/systemd/system/" directory.
Parts of the service files also exist in the following directory "/etc/systemd/system".
Service files in the directory "/etc/systemd/system" have higher priority is there is any overlap.