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       ifup - bring a network interface up

       ifdown - take a network interface down


       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...


       The   ifup   and   ifdown  commands  may  be  used  to  configure  (or,
       respectively,  deconfigure)  network  interfaces  based  on   interface
       definitions in the file /etc/network/interfaces.


       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.  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 configuration or deconfiguration of the interface.

       -h, --help
              Show summary of options.

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

       -i FILE, --interfaces=FILE
              Read   interface   definitions   from   FILE   instead  of  from

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

              Don't  run any mappings.  See interfaces(5) for more information
              about the mapping feature.

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

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


       ifup -a
              Bring   up   all   the   interfaces   defined   with   auto   in

       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.


       ifup  and  ifdown  are  actually  the  same program called by different

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


              definitions  of  network  interfaces  See interfaces(5) for more

              current state of network interfaces


       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 /var/run/network/ifstate must be writable for ifup  or  ifdown
       to  work  properly.   On  Ubuntu  the  /var/run location is a temporary
       filesystem which is always writable and thrown away on  shutdown.   You
       can also 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
       hotplug(8) or ifplugd(8).


       The     ifupdown     suite     was    written    by    Anthony    Towns


       interfaces(5), ifconfig(8).