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ifup(8)                                                                ifup(8)

NAME
       ifup - bring a network interface up

       ifdown - take a network interface down

       ifquery - parse interface configuration

SYNOPSIS
       ifup  [-nv] [--no-act] [--verbose] [-i FILE|--interfaces=FILE] [--allow
       CLASS] -a|IFACE...
       ifup -h|--help
       ifup -V|--version

       ifdown  [-nv]  [--no-act]   [--verbose]   [-i   FILE|--interfaces=FILE]
       [--allow CLASS] -a|IFACE...

       ifquery   [-nv]   [--no-act]  [--verbose]  [-i  FILE|--interfaces=FILE]
       [--allow CLASS] -a|IFACE...

       ifquery  -l|--list  [-nv]  [--no-act]  [--verbose]  [-i   FILE|--inter-
       faces=FILE] [--allow CLASS] -a|IFACE...

       ifquery --state [IFACE...]

DESCRIPTION
       The  ifup  and  ifdown  commands  may be used to configure (or, respec-
       tively, deconfigure) network interfaces based on interface  definitions
       in  the  file  /etc/network/interfaces.  ifquery command may be used to
       parse interfaces configuration.

OPTIONS
       A summary of options is included below.

       -a, --all
              If given to ifup, affect all interfaces marked auto.  Interfaces
              are  brought  up  in  the  order  in  which  they are defined in
              /etc/network/interfaces.  Combined with  --allow,  acts  on  all
              interfaces  of  a  specified class instead.  If given to ifdown,
              affect all defined interfaces.  Interfaces are brought  down  in
              the  order in which they are currently listed in the state file.
              Only  interfaces  defined  in  /etc/network/interfaces  will  be
              brought down.

       --force
              Force configuration or deconfiguration of the interface.

       --ignore-errors
              If any of the commands of scripts fails, continue.

       -h, --help
              Show summary of options.

       --allow=CLASS
              Only allow interfaces listed in an allow-CLASS line in /etc/net-
              work/interfaces to be acted upon.

       -i FILE, --interfaces=FILE
              Read interface definitions from FILE instead of  from  /etc/net-
              work/interfaces.

       -X PATTERN, --exclude=PATTERN
              Exclude  interfaces from the list of interfaces to operate on by
              the PATTERN.  PATTERN uses a usual shell glob syntax.  If  shell
              wildcards  are not used, it must match the exact interface name.
              This option may be specified multiple times  resulting  in  more
              than one pattern being excluded.

       -o OPTION=VALUE
              Set  OPTION  to  VALUE  as though it were in /etc/network/inter-
              faces.

       -n, --no-act
              Don't configure any interfaces or run any "up"  or  "down"  com-
              mands.

       --no-mappings
              Don't  run any mappings.  See interfaces(5) for more information
              about the mapping feature.

       --no-scripts
              Don't run any scripts under /etc/network/if-*.d/

       --no-loopback
              Disable special handling of the loopback interface. By  default,
              the loopback interface (lo on Linux) is predefined internally as
              an auto interface, so it's brought up on ifup -a  automatically.
              In the case the loopback device is redefined by user, the inter-
              face is configured just once anyway. If, however, another inter-
              face  is  also  defined  as  loopback, it's configured as usual.
              Specifying this option disables this behaviour, so the  loopback
              interface won't be configured automatically.

       -V, --version
              Show copyright and version information.

       -v, --verbose
              Show commands as they are executed.

       -l, --list
              For  ifquery,  list all the interfaces which match the specified
              class.  If no class specified, prints all the interfaces  listed
              as auto.

       --state
              For  ifquery,  dump  the state of the interfaces. When no inter-
              faces specified, lists all interfaces brought up  together  with
              logical interfaces assigned to them and exits with a status code
              indicating success. If one or more interfaces specified, display
              state  of  these interfaces only; successful code is returned if
              all of interfaces given as arguments are  up.  Otherwise,  0  is
              returned.

EXAMPLES
       ifup -a
              Bring  up  all  the  interfaces  defined  with auto in /etc/net-
              work/interfaces

       ifup eth0
              Bring up interface eth0

       ifup eth0=home
              Bring up interface eth0 as logical interface home

       ifdown -a
              Bring down all interfaces that are currently up.

       ifquery -l
              Print names of all interfaces specified with the auto keyword.

       ifquery -l --allow=hotplug
              Print names of all interfaces specified with  the  allow-hotplug
              keyword.

       ifquery eth0
              Display  the interface options as specified in the ifupdown con-
              figuration. Each key-value pair is  printed  out  on  individual
              line using ": " as separator.

NOTES
       ifup,  ifdown, and ifquery are actually the same program called by dif-
       ferent names.

       The program does not configure network interfaces directly; it runs low
       level utilities such as ip to do its dirty work.

       When  invoked,  ifdown  checks  if ifup is still running. In that case,
       SIGTERM is sent to ifup.

       During interface deconfiguration, ifdown ignores errors the same way as
       if --ignore-errors was specified.

FILES
       /etc/network/interfaces
              definitions  of  network  interfaces  See interfaces(5) for more
              information.

       /run/network/ifstate
              current state of network interfaces

KNOWN BUGS/LIMITATIONS
       The program keeps records of whether network interfaces are up or down.
       Under  exceptional  circumstances these records can become inconsistent
       with the real states of the interfaces.  For example, an interface that
       was  brought  up  using ifup and later deconfigured using ifconfig will
       still be recorded as up.  To fix this you can use the --force option to
       force  ifup  or ifdown to run configuration or deconfiguration commands
       despite what it considers the current state of the interface to be.

       The file /run/network/ifstate must be writable for ifup  or  ifdown  to
       work  properly.  If that location is not writable (for example, because
       the root filesystem is mounted  read-only  for  system  recovery)  then
       /run/network/ifstate should be made a symbolic link to a writable loca-
       tion.  If that is not possible then you can use the --force  option  to
       run  configuration  or  deconfiguration  commands  without updating the
       file.

       Note that the program does not run automatically: ifup alone  does  not
       bring up interfaces that appear as a result of hardware being installed
       and ifdown alone does not bring down interfaces  that  disappear  as  a
       result  of  hardware  being  removed.  To automate the configuration of
       network interfaces you need to install other packages such  as  udev(7)
       or ifplugd(8).

AUTHOR
       The   ifupdown  suite  was  written  by  Anthony  Towns  <aj@azure.hum-
       bug.org.au>.

SEE ALSO
       interfaces(5), ip(8), ifconfig(8).

IFUPDOWN                          23 May 2014                          ifup(8)



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