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.
-iFILE, --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).
