bionic (5) interfaces.5.gz

Provided by: ifupdown_0.8.17ubuntu1.1_amd64 bug

NAME

       /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.

EXAMPLE

       The following example configures two network interfaces: eth0 is brought up at boot, and  uses  DHCP  for
       IPv4  and  SLAAC  for  IPv6, whereas eth1 is brought up whenever the network hardware is detected, and is
       configured with static IPv4 and IPv6 addresses.
       auto eth0
       allow-hotplug eth1

       iface eth0 inet dhcp

       iface eth0 inet6 auto

       iface eth1 inet static
            address 192.168.1.2/24
            gateway 192.168.1.1

       iface eth1 inet6 static
            address fec0:0:0:1::2/64
            gateway fec0:0:0:1::1

FILE FORMAT

       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. These will be described in more detail in the following sections.

INTERFACE SELECTION

       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 also used by the system boot scripts, so interfaces
       marked "auto" are brought up at boot time.)  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.  (Interfaces marked "allow-hotplug" are brought up when udev detects them.  This can either
       be during boot if the interface is already present, or at a later time, for example when  plugging  in  a
       USB  network  card.   Please  note  that this does not have anything to do with detecting a network cable
       being plugged in.)

       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.

INCLUDING OTHER FILES

       Lines beginning with "source" are used to include stanzas from other files, so configuration 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 considered 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.

MAPPINGS

       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.

INTERFACE DEFINITIONS

       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.)   A list of packages providing additional options is mentioned in the section "OPTIONS PROVIDED
       BY OTHER PACKAGE".

       Options are usually indented for clarity (as in the example above) but are not required to be.

       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 interface.

INTERFACE TEMPLATES

       It is possible to define interface definition templates and extend them using the inherits keyword:

       iface ethernet inet static
            mtu 1500
            hwaddress 11:22:33:44:55:66

       iface eth0 inet static inherits ethernet
            address 192.168.1.2/24

       This  may  be  useful to separate link-level settings shared by multiple interfaces from, for example, IP
       address settings specific to every interface.

VLAN 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.

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 them with "|| 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.

       description name
              Alias interface by name

       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.
       Please  note  that  as  post-up  and  pre-down are aliases, no files in the corresponding directories are
       processed.  Please use if-up.d and if-down.d directories instead.

       All of these commands have access to the following environment variables.

       IFACE  The physical name of the interface being processed, or "--all" (see below).

       LOGICAL
              The logical name of the interface being processed, or "auto" (see below).

       ADDRFAM
              The address family of the interface, or "meta" (see below).

       METHOD The method of the interface (e.g., static), or "none" (see below).

       CLASS  The class of interfaces being processed.  This is a copy of the value given to the --allow  option
              when running ifup or ifdown, otherwise it is set to "auto" when the --all option is used.

       CLASS  The  class of interfaces being processed.  This is a copy of the value given to the --allow option
              when running ifup or ifdown, otherwise it is set to "auto" when the --all option is used.

       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.

       When  ifupdown  is  being called with the --all option, before doing anything to interfaces, if calls all
       the hook scripts (pre-up or down) with IFACE set to "--all", LOGICAL set to the current value of  --allow
       parameter  (or  "auto" if it's not set), ADDRFAM="meta" and METHOD="none".  After all the interfaces have
       been brought up or taken down, the appropriate scripts (up or post-down) are executed.

OPTIONS PROVIDED BY OTHER PACKAGES

       This manual page documents the configuration options provided by the ifupdown  package.   However,  other
       packages can make other options available for use in /etc/network/interfaces.  Here is a list of packages
       that provide such extensions:

       arping, avahi-autoipd, avahi-daemon, bind9, bridge-utils, clamav-freshclam, controlaula,  epoptes-client,
       ethtool,  guidedog,  hostap-utils, hostapd, htpdate, ifenslave, ifmetric, ifupdown-extra, ifupdown-multi,
       ifupdown-scripts-zg2, initscripts, isatapd, linux-wlan-ng, lprng,  macchanger,  miredo,  nslcd,  ntpdate,
       openntpd,  openresolv,  openssh-server,  openvpn, openvswitch-switch, postfix, resolvconf, sendmail-base,
       shorewall-init, slrn, slrnpull, tinc, ucarp, uml-utilities, uruk,  vde2,  vlan,  vzctl,  whereami,  wide-
       dhcpv6-client, wireless-tools, wpasupplicant.

       Please consult the documentation of those packages for information about how they extend ifupdown.

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/netmask) required

              netmask mask
                     Netmask (dotted quad or CIDR)

              broadcast broadcast_address
                     Broadcast address (dotted quad, + or -). Default value: "+"

              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".

              hwaddress address
                     Link local address or "random".

              mtu size
                     MTU size

              scope  Address validity scope. Possible values: global, link, host

   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

              hwaddress address
                     Link local address or "random".

              mtu size
                     MTU size

   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)

              metric metric
                     Metric for added routes (dhclient)

              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)

              hwaddress address
                     Hardware address.

   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 tunnel Method
       This  method  is  used  to  create  GRE  or IPIP tunnels. You need to have the ip binary from the iproute
       package. For GRE tunnels, you will need to load the ip_gre module and the ipip module for IPIP tunnels.

       Options

              address address
                     Local address (dotted quad) required

              mode type
                     Tunnel type (either GRE or IPIP) required

              endpoint address
                     Address of other tunnel endpoint required

              dstaddr address
                     Remote address (remote address inside tunnel)

              local address
                     Address of the local endpoint

              metric metric
                     Routing metric for default gateway (integer)

              gateway address
                     Default gateway

              ttl time
                     TTL setting

              mtu size
                     MTU size

   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).

              unit number
                     Use number as the ppp unit number.

              options string
                     Pass string as additional options to pon.

   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/wvdial.conf).

   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 auto Method
       This method may be used to define interfaces with  automatically  assigned  IPv6  addresses.  Using  this
       method  on  its  own  doesn't  mean  that RDNSS options will be applied, too. To make this happen, rdnssd
       daemon must be installed, properly configured and running. If stateless DHCPv6 support is turned on, then
       additional  network  configuration  parameters  such as DNS and NTP servers will be retrieved from a DHCP
       server. Please note that on ifdown, the lease is not currently released (a known bug).

       Options

              privext int
                     Privacy extensions (RFC4941) (0=off, 1=assign, 2=prefer)

              accept_ra int
                     Accept router advertisements (0=off, 1=on, 2=on+forwarding). Default value: "2"

              dhcp int
                     Use stateless DHCPv6 (0=off, 1=on)

              request_prefix int
                     Request a prefix through DHCPv6 Prefix Delegation (0=off, 1=on). Default value: "0"

              ll-attempts
                     Number of attempts to wait for a link-local address. Default value: "60"

              ll-interval
                     Link-local address polling interval in seconds. Default value: "0.1"

   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.  By  default,
       stateless autoconfiguration is disabled for this interface.

       Options

              address address
                     Address (colon delimited/netmask) required

              netmask mask
                     Netmask (number of bits, eg 64)

              metric metric
                     Routing metric for default gateway (integer)

              gateway address
                     Default gateway (colon delimited)

              media type
                     Medium type, driver dependent

              hwaddress address
                     Hardware address or "random"

              mtu size
                     MTU size

              accept_ra int
                     Accept router advertisements (0=off, 1=on, 2=on+forwarding)

              autoconf int
                     Perform stateless autoconfiguration (0=off, 1=on). Default value: "0"

              privext int
                     Privacy extensions (RFC3041) (0=off, 1=assign, 2=prefer)

              scope  Address validity scope. Possible values: global, site, link, host

              preferred-lifetime int
                     Time that address remains preferred

              dad-attempts
                     Number of attempts to settle DAD (0 to disable DAD). Default value: "60"

              dad-interval
                     DAD state polling interval in seconds. Default value: "0.1"

   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

              hwaddress address
                     Hardware address or "random"

              mtu size
                     MTU size

   The dhcp Method
       This method may be used to obtain network interface configuration via stateful DHCPv6 with  dhclient.  In
       stateful DHCPv6, the DHCP server is responsible for assigning addresses to clients.

       Options

              hwaddress address
                     Hardware address or "random"

              accept_ra int
                     Accept router advertisements (0=off, 1=on, 2=on+forwarding). Default value: "1"

              autoconf int
                     Perform stateless autoconfiguration (0=off, 1=on)

              request_prefix int
                     Request a prefix through DHCPv6 Prefix Delegation (0=off, 1=on). Default value: "0"

              ll-attempts
                     Number of attempts to wait for a link-local address. Default value: "60"

              ll-interval
                     Link-local address polling interval in seconds. Default value: "0.1"

   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) required

              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)

              metric metric
                     Routing metric for default gateway (integer)

              gateway address
                     Default gateway (colon delimited)

              ttl time
                     TTL setting

              mtu size
                     MTU size

              preferred-lifetime int
                     Time that address remains preferred

   The 6to4 Method
       This method may be used to setup an 6to4 tunnel. It requires the ip command from the iproute package.

       Options

              local address
                     Address of the local endpoint (IPv4 dotted quad) required

              metric metric
                     Routing metric for default gateway (integer)

              ttl time
                     TTL setting

              mtu size
                     MTU size

              preferred-lifetime int
                     Time that address remains preferred

CAN ADDRESS FAMILY

       This section documents the methods available in the can address family.

   The static Method
       This method may be used to setup an Controller Area Network (CAN)  interface.  It  requires  the  the  ip
       command from the iproute package.

       Options

              bitrate bitrate
                     bitrate (1..1000000) required

              samplepoint samplepoint
                     sample point (0.000..0.999)

              loopback loopback
                     loop back CAN Messages (on|off)

              listenonly listenonly
                     listen only mode (on|off)

              triple triple
                     activate triple sampling (on|off)

              oneshot oneshot
                     one shot mode (on|off)

              berr berr
                     activate berr reporting (on|off)

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.

AUTHOR

       The  ifupdown  suite was written by Anthony Towns <aj@azure.humbug.org.au>.  This manpage was contributed
       by Joey Hess <joey@kitenet.net>.

SEE ALSO

       ifup(8), ip(8), ifconfig(8), run-parts(8), resolvconf(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/debian-reference/ch05.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.