The server's FQDN name have to set for two purpose:
- For aestetic terms, as Daniel Lockard said
- For programs and services what uses FQDN to identify the server or as an identity, e.g. configuration manager stuffs, monitoring stuffs, Apache's ServerName, SMTP banner in most SMTP servers, etc.
There is many convention what people following to name their servers, based on served domain or giving a nick for it.
There is one convention what you have to follow: the first part of FQDN must same as the short name of the server (what you see after
@ sign at SSH prompt). So e.g. if your server name is client50 then you have to set FQDN like client50.domain.com or client50.com. It is needed because most of programs assumes the server name is predictable based on FQDN.
To set FQDN, open
/etc/hosts file with your favorite editor, and find where the 'localhost' name set (usually it's two entry: 127.0.0.1 and ::1) and set names like in following example:
127.0.0.1 client50.domain.com client50 localhost
::1 client50.domain.com client50 localhost
If your hosts file is already has a short name of server, type the choosen FQDN before the short name. Some installers are set simple name for the configured IP address of the server if you configured fix IP address during setup.