Provided by: ifupdown_0.7.47.2ubuntu4_amd64 bug

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|--interfaces=FILE] [--allow CLASS]
       -a|IFACE...

       ifquery --state [IFACE...]

DESCRIPTION

       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.
       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.

       -h, --help
              Show summary of options.

       --allow=CLASS
              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 /etc/network/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/interfaces.

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

       --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  interface  is  configured  just  once  anyway. If, however, another
              interface 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 interfaces 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/network/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 configuration. 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 different 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.

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 location.  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.humbug.org.au>.

SEE ALSO

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