Debian
In the Debian Linux Distribution, or distributions such as Ubuntu that are Debian based, the hosts file looks something like this:
127.0.0.1 localhost 127.0.1.1 <host_name> # The following lines are desirable for IPv6 capable hosts ::1 ip6-localhost ip6-loopback fe00::0 ip6-localnet ff00::0 ip6-mcastprefix ff02::1 ip6-allnodes ff02::2 ip6-allrouters ff02::3 ip6-allhosts
The IP address 127.0.1.1 in the second line is unique to Debian. The Debian Installer creates this entry for a system without a permanent IP address as a workaround for buggy software such as the Gnome desktop.
For a system with a permanent IP address, that permanent IP address should be used here instead of 127.0.1.1.
For a system with a permanent IP address and a fully qualified domain name (FQDN) provided by the Domain Name System (DNS), that canonical <host_name>.<domain_name> should be used instead of just <host_name>.