I use fresh Fedora 25 Workstation.I am practicing in network configuring and found trouble.After some time starting/stopping/restarting NetworkManager to test my configuration files it(systemd) started to show when I issuesystemctl status NetworkManager---some not important log info--- Failed to start NetworkManagerNetworkManager.service: Unit entered failed stateNetworkManager.service: Failed with result 'exit-code'.NetworkManager.service: Service hold-off time over, scheduling restartStopped Netwok Manager.NetworkManager.service: Start request repeated too quickly.Failed to start Network Manager.NetworkManager.service: Unit entered failed state.NetworkManager.service: Failed with result 'start-limit-hit'.start-limit-hit and 'repeated too quickly' have some mystery in them, extensve web searching does not give any relevant solutions.mask/unmask of network.service does not help either.systemctl start/stop network commands work without a hitch.
Why NetworkManager.service does not restart?
networking;systemd;networkmanager
I'm guessing NetworkManager is crashing when it tries to start, then it was quickly automatically being restarted, crashing many times repeatedly until it was stopped. Check sudo journatlctl to review the general system logs to see if there are some details there about why NetworkManager might be repeatedly crashing.You also say that you were testing network configuration but didn't share what changes you made. Chances are some of the changes you recently made were related. Try restoring the files you changes to their original values and see if NetworkManager starts. Then put your changes back in one-by-one to see which change triggered this issue.