The DNS settings on a CentOS virtual machine revert to defaults after a restart. What should I do?

Symptom

After restarting the CentOS virtual machine, the DNS settings revert to their defaults.

Cause

When the PEERDNS=no setting is present in the network adapter configuration file, the network interface does not automatically configure a DNS server. In this case, the DNS server must be configured manually; otherwise the virtual machine cannot resolve domain names.

Solution

• If Cloud-init is installed on the virtual machine, configure DNS in the /etc/reslove.conf file.

  [root@localhost ~]# vim /etc/reslove.conf
  #Add DNS configuration
  servername 223.5.5.5

• If Cloud-init is not installed on the virtual machine, configure the network adapter IP address and DNS address using the static method.

  [root@localhost ~]# vi /etc/sysconfig/network-scripts/ifcfg-eth0
  #Configure IP address and DNS
  DEVICE=eth0
  ONBOOT=yes
  BOOTPROTO=static
  IPADDR=192.168.1.100
  NETMASK=255.255.255.0
  GATEWAY=192.168.1.1
  DNS1=8.8.8.8
  DNS2=8.8.4.4