Linux Domain Name File. This will only list host name and will not print domain related information. If its the only default file in the root directory it automatically displays when someone goes to your domain name.
Host name file etchostname will only provide host name with fully qualified domain name. You might have guessed indexhtml file is a default file. This will only list host name and will not print domain related information.
On Alpine Linux one can use the hostname command to control the system hostname and set a new name.
The complete FQDN of the system is returned with hostname --fqdn. Use the -F or --file option to search a specific file such as hostname or hosts and change your computers hostname to match the content of the file. Its main purpose is to uniquely identify over a network. When called without any arguments hostname displays the name of the system as returned by the gethostname function.