/etc/resolv.conf is a DNS client configuration file used to set the IP address of the DNS server and the DNS domain name. It also includes the domain name search order for the host. This file is used by the resolver (a library that resolves hostnames to IP addresses). Its format is simple, with each line starting with a keyword followed by one or more parameters separated by spaces. If this file is deleted, it can cause services to be unavailable or DNS resolution to fail.