The
hosts
file contains information regarding the known hosts on the network.
For each host, a single line should be present with the following information:
Internet address
Official host name
Aliases
Items are separated by any number of blanks and/or tab characters.
A
"#"
indicates the beginning of a comment; characters up to the end of the line
are not interpreted by routines which search the file.
The system configuration file
resolv.conf(5)
controls where host name information will be searched for.
The mechanism provided permits the administrator to describe the
databases to search; the databases currently known include
yp(8),
DNS
and the
hosts
database.
When using the name server
named(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 addresses 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 database 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 database maintained at
NIC
is incomplete, use of the name server is recommended for sites on the
DARPA
Internet.
Internet addresses are specified using either
dot notation (IPv4)
or colon separated notation (IPv6).
Further information on network addressing is contained in
inet(3).
Host names may contain any printable character other than a field delimiter,
newline, or comment character.
A name server should be used instead of a static file.
Lines in
/etc/hosts
are limited to
BUFSIZ
characters
(currently 1024).
Longer lines will be ignored.