/etc/hosts                                   #Configuration of lokal DNS-resolving
/etc/HOSTNAME                                #Configuration of System Hostname

Following files are the local DNS-config files:

/etc/resolv.conf                             #Configuration of DNS-Servers
/etc/nsswitch.conf                           #Configuration how a service or a command is getting DNS-Adress (via /etc/hosts or /etc/resolv.conf)
/etc/hosts                                   #Configuration hosts file (local DNS resolution)

DNS-Name-Cache-Daemon Service on SLES-Linux:

nscd                         

Example resolv.conf

#DNS-SUFFIX for DNS resolving 
search site.example.com site.example.de       

#List of nameservers to add
nameserver 1.2.3.4
nameserver 2.3.4.5

BIND

If you want to override the DNS servers provided by DHCP entirely and force the system to use the ones you provide, use the supersede entry:

/etc/dhcp/dhclient.conf
supersede domain-name-servers 127.0.0.1;
supersede domain-name-servers 12.34.56.78, 12.34.56.79; 

cat /etc/resolv.conf
nameserver 127.0.0.1

“prepend” add servers to those provided by dhcp (work as a fallback):

prepend domain-name-servers 12.34.56.78, 12.34.56.79;