/etc/network/interfaces - network interface configuration for ifup and ifdown
DESCRIPTION
/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" and "allow-"
stanzas. Here is an example.
auto lo eth0
allow-hotplug eth1
iface lo inet loopback
mapping eth0
script /usr/local/sbin/map-scheme
map HOME eth0-home
map WORK eth0-work
iface eth0-home inet static
address 192.168.1.1
netmask 255.255.255.0
up flush-mail
iface eth0-work inet dhcp
iface eth1 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.
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/ifupdown/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 mapped.
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 logical 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" followed 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 the interface.
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 be.
IFACE OPTIONS
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 "|| true".)
pre-up command
Run
command
before bringing the interface up.
If this command fails then
ifup
aborts,
refraining from marking the interface as configured,
prints an error message,
and exits with status 0.
This behavior may change in the future.
up command
post-up command
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.
down command
pre-down command
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.
post-down command
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 behavior may change in the future.
There exists for each of the above mentioned options a directory
/etc/network/if-<option>.d/
the scripts in which are run (with no arguments) using
run-parts(8)
after the option itself has been processed.
All of these commands have access to the following environment variables.
IFACE
physical name of the interface being processed
LOGICAL
logical name of the interface being processed
ADDRFAM
address family of the interface
METHOD
method of the interface (e.g.,
static)
MODE
start if run from ifup, stop if run from ifdown
PHASE
as per MODE, but with finer granularity, distinguishing the
pre-up, post-up, pre-down and post-down phases.
VERBOSITY
indicates whether --verbose was used; set to 1 if so, 0 if not.
PATH
the command search path:
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
Additionally, all options given in an interface definition stanza are
exported to the environment in upper case with "IF_" prepended and with
hyphens converted to underscores and non-alphanumeric characters discarded.
INET ADDRESS FAMILY
This section documents the methods available in the
inet address family.
The loopback Method
This method may be used to define the IPv4 loopback interface.
Options
(No options)
The static Method
This method may be used to define ethernet interfaces with statically allocated IPv4 addresses.
Options
address address
Address (dotted quad) required
netmask netmask
Netmask (dotted quad) required
broadcast broadcast_address
Broadcast address (dotted quad)
network network_address
Network address (dotted quad) required for 2.0.x kernels
metric metric
Routing metric for default gateway (integer)
gateway address
Default gateway (dotted quad)
pointopoint address
Address of other end point (dotted quad). Note the spelling of "point-to".
media type
Medium type, driver dependent
hwaddress class address
Hardware Address. class is one of ether, ax25, ARCnet or netrom. address is dependent on the above choice.
mtu size
MTU size
The manual Method
This method may be used to define interfaces for which no configuration is done by default. Such interfaces can be configured manually by means of up and down commands or /etc/network/if-*.d scripts.
Options
(No options)
The dhcp Method
This method may be used to obtain an address via DHCP with any of the tools: dhclient, pump, udhcpc, dhcpcd. (They have been listed in their order of precedence.) If you have a complicated DHCP setup you should note that some of these clients use their own configuration files and do not obtain their configuration information via ifup.
Options
hostname hostname
Hostname to be requested (pump, dhcpcd, udhcpc)
leasehours leasehours
Preferred lease time in hours (pump)
leasetime leasetime
Preferred lease time in seconds (dhcpcd)
vendor vendor
Vendor class identifier (dhcpcd)
client client
Client identifier (dhcpcd, udhcpc)
hwaddress class address
Hardware Address. class is one of ether, ax25, ARCnet or netrom. address is dependent on this choice.
The bootp Method
This method may be used to obtain an address via bootp.
Options
bootfile file
Tell the server to use file as the bootfile.
server address
Use the IP address address to communicate with the server.
hwaddr addr
Use addr as the hardware address instead of whatever it really is.
The ppp Method
This method uses pon/poff to configure a PPP interface. See those commands for details.
Options
provider name
Use name as the provider (from /etc/ppp/peers).
The wvdial Method
This method uses wvdial to configure a PPP interface. See that command for more details.
Options
provider name
Use name as the provider (from /etc/ppp/peers).
The ipv4ll Method
This method uses avahi-autoipd to configure an interface with an IPv4 Link-Layer address (169.254.0.0/16 family). This method is also known as "APIPA" or "IPAC", and often colloquially referred to as "Zeroconf address".
Options
(No options)
IPX ADDRESS FAMILY
This section documents the methods available in the
ipx address family.
The static Method
This method may be used to setup an IPX interface. It requires the ipx_interface command.
Options
frame type
type of ethernet frames to use (e.g. 802.2)
netnum id
Network number
The dynamic Method
This method may be used to setup an IPX interface dynamically.
Options
frame type
type of ethernet frames to use (e.g. 802.2)
INET6 ADDRESS FAMILY
This section documents the methods available in the
inet6 address family.
The loopback Method
This method may be used to define the IPv6 loopback interface.
Options
(No options)
The static Method
This method may be used to define interfaces with statically assigned IPv6 addresses.
Options
address address
Address (colon delimited) required
netmask mask
Netmask (number of bits, eg 64) required
gateway address
Default gateway (colon delimited)
media type
Medium type, driver dependent
hwaddress class address
Hardware Address. class is one of ether, ax25, ARCnet or netrom. address is dependent on this choice.
mtu size
MTU size
The manual Method
This method may be used to define interfaces for which no configuration is done by default. Such interfaces can be configured manually by means of up and down commands or /etc/network/if-*.d scripts.
Options
(No options)
The v4tunnel Method
This method may be used to setup an IPv6-over-IPv4 tunnel. It requires the ip command from the iproute package.
Options
address address
Address (colon delimited)
netmask mask
Netmask (number of bits, eg 64)
endpoint address
Address of other tunnel endpoint (IPv4 dotted quad) required
local address
Address of the local endpoint (IPv4 dotted quad)
gateway address
Default gateway (colon delimited)
ttl time
TTL setting
KNOWN BUGS/LIMITATIONS
The
ifup
and
ifdown
programs work with so-called "physical" interface names.
These names are assigned to hardware by the kernel.
Unfortunately it can happen that the kernel assigns different
physical interface names to the same hardware at different
times; for example, what was called "eth0" last time you booted
is now called "eth1" and vice versa.
This creates a problem if you want to configure the interfaces
appropriately.
A way to deal with this problem is to use mapping scripts that
choose logical interface names according to the properties of
the interface hardware.
See the
get-mac-address.sh
script in the examples directory for an example of such a mapping
script. See also Debian bug #101728.
It is not currently possible to divide up
/etc/network/interfaces
into multiple files. A feature that would make this possible is
some sort of inclusion directive. No such feature exists in the
current ifupdown program. For more information see Debian
bug #159884.
ifup(8),
iwconfig(8),
run-parts(8).
For advice on configuring this package read the
Network Configuration
chapter of the Debian Reference manual,
available at
http://www.debian.org/doc/manuals/reference/ch-gateway.en.html
or in the debian-reference-en package.
Examples of how to set up interfaces can be found in
/usr/share/doc/ifupdown/examples/network-interfaces.gz.
