Where in system configuration files is the DNS server usually specified and changed if necessary?

In Linux systems, DNS servers are usually specified in the /etc/resolv.conf file. This file contains the DNS server addresses in the following format:

nameserver 8.8.8.8
nameserver 8.8.4.4

However, in modern systems using systemd-resolved or NetworkManager, this file may be automatically generated, and changes to it can be overwritten.

In such cases, DNS servers are configured via:

• NetworkManager: through the graphical interface or the nmcli command.
• systemd-resolved: in the /etc/systemd/resolved.conf file or via resolvectl.

In Windows, DNS servers are configured in the network connection properties or through the netsh command.

Thus, the main file for directly specifying DNS is /etc/resolv.conf, but in modern systems, it is important to consider network managers and services that may manage this file.