Ubuntu Manpage: ifup - bring a network interface up

Provided by: ifupdown_0.8.35ubuntu1_amd64

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 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/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 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.

       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  result 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 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).

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.