How Do You Get a NIC on a Linux Server to Work?

Problem scenario
Your NIC on your Fedora Linux server totally will not work. The physical NIC has no lights on it. It seems it is disabled. You cannot enable it with commands.

You see errors like these in logs: "NetworkManager.service: Start request repeated too quickly."

What should you do?

Solution
Run this command:

journalctl -u NetworkManager

Do you see lines like these?

Jan 25 20:47:00 localhost.localdomain systemd[1]: NetworkManager.service: Scheduled restart job, restart counter is at 5.
Jan 25 20:47:00 localhost.localdomain systemd[1]: Stopped Network Manager.
Jan 25 20:47:00 localhost.localdomain systemd[1]: NetworkManager.service: Start request repeated too quickly.
Jan 25 20:47:00 localhost.localdomain systemd[1]: NetworkManager.service: Failed with result 'exit-code'.
Jan 25 20:47:00 localhost.localdomain systemd[1]: Failed to start Network Manager.
lines 5443-5479/5479 (END)

Look for a line like this (and it may be subtle in the logs in gray text):

Jan 25 20:47:00 localhost.localdomain NetworkManager[3454]: /usr/sbin/NetworkManager: error while loading shared libraries: foobar.so.4: cannot open shared object file>

Try to find the foobar.so.4 file (e.g., with sudo find / -name foobar.so.4). It could be a lib.so file. Have the permissions changed? Was the file deleted? You may need to run sudo chmod u+r,g+x foobar.so.4 to get it to be executable.

A downside to color-coded logs is that sometimes they bring your attention to irrelevant details and contribute to you overlooking important details.