.TH INTERFACES 5 "25 May 2007" "config files" "GNU/Linux System Architect Toolkit"
.SH NAME
interfaces \- network interface configuration file
.SH DESCRIPTION
.I /etc/interfaces
is a text file containing a list of the system's network interfaces and their parameters.  The information in
.I /etc/interfaces
is passed to the
.BR ifconfig
command by the system start-up scripts.  Each line describes the parameters for one interface and typically has the following format:
.PP
.RS
if-name ip-address network-mask
.RE
.PP
The field descriptions are:
.RS
.TP
.I if-name
the name of the interface being configured
.TP
.I ip-address
the IP address to be assigned to the interface
.TP
.I network-mask
the network mask to be assigned to the interface
.RE
.PP
Other parameters may also be used.  Anything that can be passed as an argument to
.BR ifconfig
is acceptable.
.SH NOTE
Lines beginning with hash marks (#) are treated as comments.
.SH EXAMPLE
The following is an annotated example of the
.I /etc/interfaces
file that might be used in a typical home networking environment.
.RS
.TP
# loopback interface
this line is a comment
.TP
lo 127.0.0.1 255.0.0.0
configures the loopback interface with an IP address of 127.0.0.1 and a network mask of 255.0.0.0
.TP
# primary ethernet interface
this line is a comment
.TP
eth0 192.168.1.5
configures the first ethernet adapter with an IP address of 192.168.1.5.  A network mask of 255.255.255.0 is assumed, because 192.168.1.5 is a class C address.
.RE
.SH BUGS
Hash marks (#) that are not followed by some sort of whitespace will not be interpreted as comments.
.SH "SEE ALSO"
.BR ifconfig (8)
.BR routes (5)
.SH AUTHOR
David Horton (http://www.happy-monkey.net/architect)