====== ifup / ifdown / ifquery ======

  * [[Networking]]
  * [[Ubuntu Networking]]
  * [[ifconfig]]
  * [[ifenslave]]
  * [[ip]]

  * **ifup** - bring a network interface up
  * **ifdown** - take a network interface down
  * **ifquery** - parse interface configuration\

''ifup'', ''ifdown'', and ''ifquery'' are shipped with Ubuntu to manage network interfaces. The interface configurations are set in ''/etc/network/interfaces''. See also ''man interfaces''.

The state of the interfaces is located in ''/run/network/interfaces''. If one is up or down, but not showing in the list with ''ifquery'' or in the file, you can use ''--force'' to have it be recorded in a certain state.

For example, if you brought an interface up (or down) using another program, and ''ifup'' or ''ifdown'' don't show the same state in ''ifquery'' or the ''run'' file, set the state directly using ''--force''.

=== ifup ===

  * **-a** - load configuration for all devices marked ''auto''
  * **--force** - force configuration
  * **-i** - read configuration from ''file'' instead of ''/etc/network/interfaces''
  * **-o** option:value - set option to value manually
  * **-v** - verbose output

=== ifdown ===

  * **-a** - brings down all devices configured in the ''interfaces'' file
  * **--force** - force configuration
  * **-i** - read configuration from ''file'' instead of ''/etc/network/interfaces''
  * **-o** option:value - set option to value manually
  * **-v** - verbose output

=== ifquery ===

  * **-l** or **--list** - list all interfaces
  * **--state** device - dump the state of the interfaces; all if no device specified

=== Scenarios ===

If you want to force reset an interface completely, so that you can restart from scratch using the configuration in ''interfaces'', here's how:

First, remove the IP address from the interface:

<code>
ifconfig eth0 0
</code>

Then, force the device to not be considered as up by ''ifup'', ''ifdown'' or ''ifquery'':

<code>
ifdown --force eth0
</code>

Finally, bring it back online using ''interfaces'' config:

<code>
ifup eth0
</code>