you’d use “order (Medical web site) bind,hosts”, and in an /etc/nsswitch.conf
you’d use “order bind,hosts”, and in an /etc/nsswitch.conf file you’d use “hosts: dns files”, to make the resolver fall back to the hosts file if the central name server is unreachable. How DNS Works DNS organizes hostnames in a domain hierarchy. A domain is a collection of sites that are related in some sense — because they form a proper network (e.g., all machines on a campus, or all hosts on BITNET), because they all belong to a certain organization (e.g., the U.S. government), or because they’re simply geographically close. For instance, universities are commonly grouped in the edu domain, with each university or college using a separate subdomain, below which their hosts are subsumed. Groucho Marx University have the groucho.edu domain, while the LAN of the Mathematics department is assigned maths.groucho.edu. Hosts on the departmental network would have this domain name tacked onto their hostname, so erdos would be known as erdos. maths.groucho.edu. This is called the fully qualified domain name (FQDN), which uniquely identifies this host worldwide. Figure 6.1 shows a section of the namespace. The entry at the root of this tree, which is denoted by a single dot, is quite appropriately called the root domain and encompasses all other domains. To indicate that a hostname is a fully qualified domain name, rather than a name relative to some (implicit) local domain, it is sometimes written with a trailing dot. This dot signifies that the name’s last component is the root domain. Figure 6.1: A part of the domain namespace Depending on its location in the name hierarchy, a domain may be called top-level, second-level, or third-level. More levels of subdivision occur, but they are rare. This list details several top-level domains you may see frequently: Domain Description edu (Mostly U.S.) educational institutions like universities. com Commercial organizations and companies. org Non-commercial organizations. Private UUCP networks are often in this domain. net Gateways and other administrative hosts on a network.