[CentOS] KVM Client NetworkManager Problem

Sat Dec 15 17:27:39 UTC 2018
Gregory P. Ennis <PoMec at PoMec.Net>


On my systems I have after update to last centos 1810 a big Problem with the 

Om my system I have three NIC two are connected from hardware (hostdev) the 
last is connected from the bridge on the host. (NetworkManager was disabled)

Now after the update the client can't start the NIC's correctly :-(
My Problem is the bridged NIC ethX

I must Install and activate the NetworkManager or I have a LSB Error
[ INFO ] Network Manager is not active.
[DEPEND] Dependency failed for Network Manager Wait Online.
         Starting LSB: Bring up/down networking...
[FAILED] Failed to start LSB: Bring up/down networking.

But now NetworkManager create sometimes a new config for a new ethX this is 
configured from dhcp, but I must have a static address to connect other server 

Also the resolv.conf is overwritten and have wrong nameserver (ipv6)  and 
duplicate search entries ...

Now it is the Problem after a reboot the network is not running correct with 
or without NetworkManager?

Thanks for a answer or help, 



I have two units that are different users with desktop KVM hypervisors Centos 7 hosts.  One
had only one network card and it went through the migration from 7.5 to 7.6 without a
problem.  The other had three network cards and it became disabled with failed network
connections. I had to rebuild the network and did so in the following manner.

#1. NetworkManager had been turned off.  I turned NetworkManger from off to on so that it
would create appropriate ifcfg-* files for three network cards after a reboot.

#2.  I modified the appropriate ifcf-* files and created a new network bridge with one of
the cards.  After the update to 7.6 I was able to leave NetworkManager running as long as I
had the appropriate ifcf-* file and the bridge set with “NM_CONTROLLED=no”.  With Centos
7.5 I had to disable NetworkManager because it kept destroying the bridge even with the
switch “NM_CONTROLLED=no”. 

#3.  Lastly I had to change the references to the new bridge in the KVM guests.

After this everything has worked like it did before the upgrade.  My take on this is that
kvm hypervisors that are set up with more than one nic card have the potential of having
their network setup corrupted when the migration from 7.5 to 7.6 occurs.  On a positive
note NetworkManager now works with a network bridge with 7.6, but it did not work for me
with 7.5.

Good Luck!!!