NAME
ifup - bring a network interface up
ifdown - take a network interface down
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...
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.
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. 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.
-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.
-V, --version
Show copyright and version information.
-v, --verbose
Show commands as they are executed.
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.
NOTES
ifup and ifdown are actually the same program called by different
names.
The program does not configure network interfaces directly; it runs low
level utilities such as ifconfig and route to do its dirty work.
FILES
/etc/network/interfaces
definitions of network interfaces See interfaces(5) for more
information.
/var/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 /var/run/network/ifstate must be writable for ifup or ifdown
to work properly. On Ubuntu the /var/run location is a temporary
filesystem which is always writable and thrown away on shutdown. You
can also 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
hotplug(8) or ifplugd(8).
AUTHOR
The ifupdown suite was written by Anthony Towns
<aj@azure.humbug.org.au>.
SEE ALSO
interfaces(5), ifconfig(8).