NAME
hosts —
host name data base
DESCRIPTION
The
hosts file contains information regarding the known hosts
on the network. It can be used in conjunction with the DNS, and the NIS maps
‘hosts.byaddr’, and ‘hosts.byname’, as controlled by
nsswitch.conf(5).
For each host a single line should be present with the following information:
address hostname [alias ...]
These are:
- address
- Internet address
- hostname
- Official host name
- alias
- Alias host name
Items are separated by any number of blanks and/or tab characters. A hash sign
(“#”) indicates the beginning of a comment; characters up to the
end of the line are not interpreted by routines which search the file.
When using the name server
named(8), or
ypserv(8), this file provides a
backup when the name server is not running. For the name server, it is
suggested that only a few addresses be included in this file. These include
address for the local interfaces that
ifconfig(8) needs at boot time
and a few machines on the local network.
This file may be created from the official host data base maintained at the
Network Information Control Center (NIC), though local changes may be required
to bring it up to date regarding unofficial aliases and/or unknown hosts. As
the data base maintained at NIC is incomplete, use of the name server is
recommended for sites on the DARPA Internet.
As network addresses, both IPv4 and IPv6 addresses are allowed. IPv4 addresses
are specified in the conventional dot (“.”) notation using the
inet_pton(3) routine from the
Internet address manipulation library,
inet(3). IPv6 addresses are
specified in the standard hex-and-colon notation. Host names may contain any
printable character other than a field delimiter, newline, or comment
character.
FILES
- /etc/hosts
- The hosts file resides in
/etc.
SEE ALSO
gethostbyname(3),
nsswitch.conf(5),
ifconfig(8),
named(8)
Name Server Operations Guide for
BIND.
HISTORY
The
hosts file format appeared in
4.2BSD.