Disable NetworkManager Service in Linux OS
Often it can happen that you need to update the network settings in Linux OS (I am referring to CentOS and RHEL 6.x distributions) and unlike Windows which is GUI driven, the most convenient way is to update the following files under /etc/sysconfig/network-scripts/ifcfg-ethX where X can be the network interface assigned to your VM or hardware. You can check your network interfaces with the following command: # ifconfig.
We recently had to change the network interface settings and for that I had edited the ifcfg-eth file manually through the linux console. However, after flushing the ip route and restarting the network, the following message was being displayed:
RTNETLINK answers: file exists
Also, running the ifconfig command also showed that the network was misconfigured even though you had the following lines added to your ifcfg file:
After much attempts, it turned out that you had to disable the NetworkManager service as that was conflicting with the manual edits which I was making and not allowing it to take effect.
To disable NetworkManager, run the following commands:
# chkconfig –level 0123456 NetworkManager off
# service NetworkManager stop
# chkconfig –level 35 network on
Also ensure that NM_CONTROLLED=no is present on the ifcfg file and then run the following commands again:
# ip route flush all
# service network restart
Hopefully, your network connectivity would be restored and you can also try rebooting the server to ensure that the changes are in place even after a reboot.