Linux Etc Domain Name. The recommended method of setting the FQDN is to make the hostname be an alias for the fully qualified name using host file ie etchosts DNS or NIS. The Domain Name Service DNS provides a mechanism to associate one or more alphanumeric names with a numeric IP address.
Host name can be get with different ways in Linux. Using the etchosts file you are essentially overriding the DNS server. For example server1cybercitibiz is FQDN.
Before moving any further you should understand a few things about another important file that is etcnsswitchconf.
The etcresolvconf is the main configuration file for the DNS name resolver library. Programs that need to lookup the numeric IP address for a name issue calls to this library. Get Host name By Echoing Host name File Host name information is stored in a file etchostname. In the networking terminology the domain name is the mapping of IP with the name.