INTERFACES(5) File formats INTERFACES(5)
/etc/network/interfaces - network interface configuration for ifup and ifdown
/etc/network/interfaces contains network interface configuration information for the
ifup(8) and ifdown(8) commands. This is where you configure how your system is connected
to the network.
Lines starting with `#' are ignored. Note that end-of-line comments are NOT supported,
comments must be on a line of their own.
A line may be extended across multiple lines by making the last character a backslash.
The file consists of zero or more "iface", "mapping", "auto", "allow-", "source" and
"source-directory" stanzas. Here is an example:
iface eth0 inet dhcp
iface eth0 inet6 auto
map HOME eth0-home
map WORK eth0-work
iface eth1-home inet static
iface eth1-work inet dhcp
Lines beginning with the word "auto" are used to identify the physical interfaces to be
brought up when ifup is run with the -a option. (This option is used by the system boot
scripts.) Physical interface names should follow the word "auto" on the same line. There
can be multiple "auto" stanzas. ifup brings the named interfaces up in the order listed.
Lines beginning with "allow-" are used to identify interfaces that should be brought up
automatically by various subsytems. This may be done using a command such as "ifup
--allow=hotplug eth0 eth1", which will only bring up eth0 or eth1 if it is listed in an
"allow-hotplug" line. Note that "allow-auto" and "auto" are synonyms.
Lines beginning with "no-auto-down" are used to identify interfaces that should not be
brought down by the command "ifdown -a". Its main use is to prevent an interface from
being brought down during system shutdown time, for example if the root filesystem is a
network filesystem and the interface should stay up until the very end. Note that you can
still bring down the interface by specifying the interface name explicitly.
Lines beginning with "no-scripts" are used to identify interfaces for which scripts in
/etc/network/if-*.d/ should not be run when those interfaces are brought up or down.
Lines beginning with "source" are used to include stanzas from other files, so configura‐
tion can be split into many files. The word "source" is followed by the path of file to be
sourced. Shell wildcards can be used. (See wordexp(3) for details.)
Similarly, "source-directory" keyword is used to source multiple files at once, without
specifying them individually or using shell globs. Additionally, when "source-directory"
is used, names of the files are checked to match the following regular expression:
^[a-zA-Z0-9_-]+$. In other words, the names must consist entirely of ASCII upper- and
lower-case letters, ASCII digits, ASCII underscores, and ASCII minus-hyphens. In the
directory path, shell wildcards may be used as well.
When sourcing files or directories, if a path doesn't have a leading slash, it's consid‐
ered relative to the directory containing the file in which the keyword is placed. In the
example above, if the file is located at /etc/network/interfaces, paths to the included
files are understood to be under /etc/network.
Currently, "source-directory" isn't supported by network-manager and guessnet.
By default, on a freshly installed Debian system, the interfaces file includes a line to
source files in the /etc/network/interfaces.d directory.
Stanzas beginning with the word "mapping" are used to determine how a logical interface
name is chosen for a physical interface that is to be brought up. The first line of a
mapping stanza consists of the word "mapping" followed by a pattern in shell glob syntax.
Each mapping stanza must contain a script definition. The named script is run with the
physical interface name as its argument and with the contents of all following "map" lines
(without the leading "map") in the stanza provided to it on its standard input. The script
must print a string on its standard output before exiting. See /usr/share/doc/ifup‐
down/examples for examples of what the script must print.
Mapping a name consists of searching the remaining mapping patterns and running the script
corresponding to the first match; the script outputs the name to which the original is
ifup is normally given a physical interface name as its first non-option argument. ifup
also uses this name as the initial logical name for the interface unless it is accompanied
by a suffix of the form =LOGICAL, in which case ifup chooses LOGICAL as the initial logi‐
cal name for the interface. It then maps this name, possibly more than once according to
successive mapping specifications, until no further mappings are possible. If the
resulting name is the name of some defined logical interface then ifup attempts to bring
up the physical interface as that logical interface. Otherwise ifup exits with an error.
Stanzas defining logical interfaces start with a line consisting of the word "iface" fol‐
lowed by the name of the logical interface. In simple configurations without mapping
stanzas this name should simply be the name of the physical interface to which it is to be
applied. (The default mapping script is, in effect, the echo command.) The interface
name is followed by the name of the address family that the interface uses. This will be
"inet" for TCP/IP networking, but there is also some support for IPX networking ("ipx"),
and IPv6 networking ("inet6"). Following that is the name of the method used to configure
Additional options can be given on subsequent lines in the stanza. Which options are
available depends on the family and method, as described below. Additional options can be
made available by other Debian packages. For example, the wireless-tools package makes
available a number of options prefixed with "wireless-" which can be used to configure the
interface using iwconfig(8). (See wireless(7) for details.)
Options are usually indented for clarity (as in the example above) but are not required to
Multiple "iface" stanzas can be given for the same interface, in which case all of the
configured addresses and options for that interface will be applied when bringing up that
interface. This is useful to configure both IPv4 and IPv6 addresses on the same interface
(although if no inet6 stanza is present, the kernel will normally still perform stateless
address autoconfiguration if there is an IPv6 route advertisement daemon on the network).
It can also be used to configure multiple addresses of the same type on a single inter‐
It is possible to define interface definition templates and extend them using the inherits
iface ethernet inet static
iface eth0 inet static inherits ethernet
This may be useful to separate link-level settings shared by multiple interfaces from, for
example, IP address settings specific to every interface.
VLAN AND BRIDGE INTERFACES
To ease the configuration of VLAN interfaces, interfaces having . (full stop character)
in the name are configured as 802.1q tagged virtual LAN interface. For example, interface
eth0.1 is a virtual interface having eth0 as physical link, with VLAN ID 1.
For compatibility with bridge-utils package, if bridge_ports option is specified, VLAN
interface configuration is not performed.
The following "command" options are available for every family and method. Each of these
options can be given multiple times in a single stanza, in which case the commands are
executed in the order in which they appear in the stanza. (You can ensure a command never
fails by suffixing them with "|| true".)
Run command before bringing the interface up. If this command fails then ifup
aborts, refraining from marking the interface as configured, prints an error mes‐
sage, and exits with status 0. This behavior may change in the future.
Run command after bringing the interface up. If this command fails then ifup
aborts, refraining from marking the interface as configured (even though it has
really been configured), prints an error message, and exits with status 0. This
behavior may change in the future.
Run command before taking the interface down. If this command fails then ifdown
aborts, marks the interface as deconfigured (even though it has not really been
deconfigured), and exits with status 0. This behavior may change in the future.
Run command after taking the interface down. If this command fails then ifdown
aborts, marks the interface as deconfigured, and exits with status 0. This behav‐
ior may change in the future.
There exists for each of the above mentioned options a directory /etc/net‐