In CentOS or Red Hat Enterprise Linux (RHEL) 7, you can find your
/etc/resolv.conf file, which holds all nameserver configurations for your server, to be overwritten by the NetworkManager.
If you check the content of
/etc/resolv.conf, it may look like this.
$ cat /etc/resolv.conf # Generated by NetworkManager search mydomain.tld nameserver 126.96.36.199
The NetworkManager will assume it has the rights to control
/etc/resolv.conf, if it finds a DNS related configuration in your interface configuration file.
$ grep DNS /etc/sysconfig/network-scripts/ifcfg-* DNS1="188.8.131.52" IPV6_PEERDNS="yes"
To prevent Network Manager to overwrite your
resolv.conf changes, remove the DNS1, DNS2, ... lines from
Now, you can manually change the
/etc/resolv.conf file again, and you should be good to go. NetworkManager will no longer overwrite your DNS nameserver configurations.