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] [--state-dir=DIR] [--allow CLASS] -a|IFACE...
       ifup -h|--help
       ifup -V|--version

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

       ifquery [-nv] [--verbose] [-i FILE|--interfaces=FILE] [--state-dir=DIR] [--allow CLASS] IFACE...

       ifquery -l|--list [-nv] [--verbose] [-i FILE|--interfaces=FILE] [--state-dir=DIR] [--allow CLASS] [-a|IFACE...]

       ifquery --state [--state-dir=DIR] [--allow CLASS] [-a|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  de‐
              fined  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/network/interfaces to be acted upon.

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

       --state-dir=DIR
              Keep interface state in DIR instead of in /run/network.

       -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  re‐
              defined  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 inter‐
              faces 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  argu‐
              ments 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 indi‐
              vidual 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.

       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

CONCURRENCY
       Ifupdown uses per-interface locking to ensure that concurrent ifup and ifdown calls to the same interface are run in serial.
       However, calls to different interfaces will be able to run in parallel.

EXIT STATUS
       For  ifup  and  ifdown,  the exit status will be 0 if the given interface(s) have all been (de)configured successfully, 1 if
       there was any error.  The result of these commands is idempotent; running ifup on an interface that is already up  will  re‐
       sult  in an exit status of 0, and similarly running ifdown on an interface that is not up will also result in an exit status
       of 0.

       ifquery will normally return with exit status 0 if an interface with a matching iface stanza, 1  if  there  is  no  matching
       stanza.  ifquery --state will also return with exit status 1 if the given interface was known but was not up.

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 hard‐
       ware 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).

AUTHORS
       The  ifupdown  suite  was  created  by  Anthony  Towns <aj@azure.humbug.org.au>, and is currently maintained by Guus Sliepen
       <guus@debian.org>.

       Many others have helped develop ifupdown over time, see /usr/share/doc/ifupdown/changelog.Debian.gz for a full history.

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

IFUPDOWN                                                    11 Jan 2017                                                     ifup(8)

Usage: ifdown <options> <ifaces...>

Options:
        -h, --help             this help
        -V, --version          copyright and version information
        -a, --all              process all interfaces marked "auto"
        --allow CLASS          ignore non-"allow-CLASS" interfaces
        -i, --interfaces FILE  use FILE for interface definitions
        --state-dir DIR        use DIR to store state information
        -X, --exclude PATTERN  exclude interfaces from the list of
                               interfaces to operate on by a PATTERN
        -n, --no-act           print out what would happen, but don't do it
                               (note that this option doesn't disable mappings)
        -v, --verbose          print out what would happen before doing it
        -o OPTION=VALUE        set OPTION to VALUE as though it were in
                               /etc/network/interfaces
        --no-mappings          don't run any mappings
        --no-scripts           don't run any hook scripts
        --no-loopback          don't act specially on the loopback device
        --force                force de/configuration
        --ignore-errors        ignore errors