Because network connection names usually correspond to the machine's hostname, these network connection names are commonly referred to as "hostnames," but this can be misleading. The actual hostname is defined in the /etc/sys_id file. By default, this hostname is used as the network connection name for the machine's primary network interface, but this behavior is configurable. A machine with multiple network interfaces has multiple network connection names associated with it. By convention, each of these connection names contains the hostname--for example, if the host "fruit" acts as a gateway between two networks in the "salad.com" domain, it might use these names:
fruit.salad.com gate-fruit.salad.comThe process of mapping network connection names to IP addresses is commonly called hostname resolution. There are several different systems for hostname resolution. Machines can use a local database (the /etc/hosts database), or they can obtain information from servers on the network, using either the Network Information Service (NIS) or the Domain Name System (DNS). The following sections describe the advantages and drawbacks of the different systems: