ifup(8) 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|--inter-
faces=FILE] [--allow CLASS] -a|IFACE...
ifquery --state [IFACE...]
DESCRIPTION
The ifup and ifdown commands may be used to configure (or, respec-
tively, 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/net-
work/interfaces to be acted upon.
-i FILE, --interfaces=FILE
Read interface definitions from FILE instead of from /etc/net-
work/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/inter-
faces.
-n, --no-act
Don't configure any interfaces or run any "up" or "down" com-
mands.
--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 inter-
face is configured just once anyway. If, however, another inter-
face 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 inter-
faces 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/net-
work/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 con-
figuration. 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 dif-
ferent 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 loca-
tion. 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.hum-
bug.org.au>.
SEE ALSO
interfaces(5), ip(8), ifconfig(8).
IFUPDOWN 22 May 2004 ifup(8)
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