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] [--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.

--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.

-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

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).