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What is the Hosts file?

Updated:  10/30/2013 07:10 AM
Author:  Shiju Mathews

Status:    Resolved.

The hosts file is a computer file used by an operating system to map hostnames to IP addresses. The hosts file is a plain text file, and is conventionally named hosts.
The hosts file is one of several system facilities that assists in addressing network nodes in a computer network. It is a common part of an operating system's Internet Protocol (IP) implementation, and serves the function of translating human-friendly hostnames into numeric protocol addresses, called IP addresses, that identify and locate a host in an IP network.
In some operating systems, the contents of the hosts file is used preferentially to other name resolution methods, such as the Domain Name System (DNS), but many systems implement name service switches, e.g., nsswitch.conf for Linux and Unix, to provide customization. Unlike remote DNS resolvers, the hosts file is under the direct control of the local computer's administrator.
The hosts file contains lines of text consisting of an IP address in the first text field followed by one or more host names. Each field is separated by white space (blanks or tabulation characters). Comment lines may be included; they are indicated by a hash character (#) in the first position of such lines. Entirely blank lines in the file are ignored.

For reference the HOSTS file is located in the following locations for the listed operating systems:

Operating System Location on Hard Drive
Linux/Unix /etc/hosts
Windows 3.1/95/98/ME c:\windows\hosts
Windows NT/2000/XP Pro c:\winnt\system32\drivers\etc\hosts
Windows XP Home c:\windows\system32\drivers\etc\hosts
Windows 7 c:\windows\system32\drivers\etc\hosts
Windows 8 c:\windows\system32\drivers\etc\hosts
Apple System Folder:Preferences and in the System Folder itself.