is a daemon that responds to network link events from the Linux
kernel, such as a network interface losing or acquiring a carrier
When an Ethernet-style network interface on a host is plugged into a
powered-up switch, hub, or other host, the two use a carrier signal to
establish that the link is alive. The Linux kernel makes this
information available through its
daemon listens for carrier detection and loss messages from the
subsystem. When a carrier signal is detected on an interface, it runs
a script to bring the interface up. When carrier is lost,
runs a script to bring the interface down.
does not define any policies for how to manage interfaces; it leaves
that to a script,
which is described in
which interfaces it should manage by giving it a list of shell-style
glob patterns, which it matches against using the
function. For example, a pattern of
to only manage
if those interfaces exist. If the interfaces are not known to the
kernel at the time you start
perhaps because they are unplugged PCMCIA network interfaces or
devices whose drivers have not yet been installed,
will start to manage them as soon as they are plugged in or their
drivers are available.
Run in the foreground; do not detach and run as a daemon. Messages
are logged to
instead of using the
mechanism. This option is useful mainly for debugging your
Prevent autoprobing for interfaces. The
daemon normally probes for all possible interface names that might
match the patterns you tell it to manage. This is necessary in order
to get network driver modules (the default with almost all Linux
distributions) loaded and set up, so that they can provide link status
notifications to the
daemon. Autoprobing should always be safe, and doesn't take long.
Disable it with caution.
Specify the name of a file from which to read patterns that describe
the interfaces to manage. You can provide this option multiple times to read
from more than one file. If you do not provide this option at all,
will attempt to read from a default config file. If you do not want
to try to read from any real config files, you can specify
as a config file.
Specify a pattern that will be used to match interface names that
should manage. You can provide this option multiple times to specify
Write the daemon's process ID to the file
If you tell
to run in the foreground, this option is ignored.
Default config file to read, if none is specified on the command line.
The config file format is one pattern per line, with white space,
empty lines, and comments starting with a
character ignored. Patterns are standard shell-style glob patterns,
The "policy" program (typically a shell script) that
uses to probe for interfaces, and to bring them up or down in response
to network link events. This program is called with the name of the
interface as its first argument, and one of the following options:
A cable was plugged in, or carrier came up. The command should bring
the interface up. The command is run asynchronously, and it should
exit with status 0 on success.
A cable was plugged out, or carrier went down. The command should
bring the interface down. The command is run asynchronously, and it should
exit with status 0 on success.
The command should load and initialise the driver for this interface,
if possible, and bring the interface into the "up" state, so that it
events. The command is run synchronously; it must exit with status
code 0 if it succeeds, otherwise with a non-zero exit code or signal.
script that starts, stops, and displays status of the
Copyright 2003 PathScale, Inc.
Copyright 2003, 2004, 2005 Bryan O'Sullivan
is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License, version 2, as published by
the Free Software Foundation. You are forbidden from redistributing
or modifying it under the terms of any other license, including other
versions of the GNU General Public License.
is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.