On Linux systems, the DNS client is configured through the /etc/resolv.conf file, which contains nameserver IP addresses, search domains, and other resolver options. This file is read by the DNS resolver library to determine which DNS servers to query. The /etc/hostname file (A) stores the system hostname, /etc/sysconfig/network (C) is for Red Hat-style network configuration, and /etc/named.conf (D) is for configuring a DNS server (not client).