Setting DNS centos 7

Configure static DNS in /etc/sysconfig/network-scripts/ifcfg-ethX

If you disabled Network Manager, but use network service instead, you can use interface configuration files (e.g., /etc/sysconfig/network-scripts/ifcfg-eth0) to specify static DNS. In this case, there are actually two ways to do it.

Method One

Use "PEERDNS=no". This option will prevent /etc/resolv.conf from being modified by a DHCP server. So instead of using DHCP-provided DNS, you can specify any arbitrary DNS servers you want to use in /etc/resolv.conf.

The configuration file for your network interface (e.g., eth0) looks like the following.

$ sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0

DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes
PEERDNS=no

Then, add static DNS to /etc/resolv.conf

$ sudo vi /etc/resolv.conf

nameserver 8.8.8.8
nameserver 8.8.4.4

Method Two

Alternatively, you can specify DNS servers directly in the interface configuration file, instead of modifying /etc/resolv.conf yourself. That is:

$ sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0

DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes
DNS1=8.8.8.8
DNS2=8.8.4.4

The DNS servers specified with "DNS1/DNS2" directives will then automatically be added to /etc/resolv.conf when the interface is activated. So there is no need to modify /etc/resolv.conf yourself.

The above two methods can be applied similarly to a static IP address case. That is:

DEVICE=eth0
BOOTPROTO=manual
ONBOOT=yes
IPADDR=10.0.1.27
NETWORK=10.0.1.0
NETMASK=255.255.255.0
PEERDNS=no  (then add DNS to /etc/resolv.conf)

Or:

DEVICE=eth0
BOOTPROTO=manual
ONBOOT=yes
IPADDR=10.0.1.27
NETWORK=10.0.1.0
NETMASK=255.255.255.0
DNS1=8.8.8.8
DNS2=8.8.4.4