ifup(8) ifup(8)
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/net-
work/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.
-e PATTERN, --exclude=PATTERN
Exclude interfaces from the list of interfaces to operate on by the PATTERN. Notice that the PATTERN can be a full interface name
or substrings that match interfaces. Users could easily have unexpected behaviour if they use a small string to do the match.
-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 ip 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 inconsis-
tent with the real states of the interfaces. For example, an interface that was brought up using ifup and later deconfigured using ifcon-
fig will still be recorded as up. To fix this you can use the --force option to force ifup or ifdown to run configuration or deconfigura-
tion 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 deconfigura-
tion 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 configura-
tion 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), ip(8), ifconfig(8).
IFUPDOWN
22 May 2004 ifup(8)