netplugd — network cable hotplug management daemon
netplugd [-FP] [-c config_file] [-i interface_pattern] [-p pid_file]
netplugd is a daemon that responds to network link events from the Linux
kernel, such as a network interface losing or acquiring a carrier signal.
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 netlink(7) interface.
The netplugd daemon listens for carrier detection and loss messages from
the kernel's netlink(7) subsystem. When a carrier signal is detected on
an interface, it runs a script to bring the interface up. When carrier
is lost, netplugd runs a script to bring the interface down. netplugd
does not define any policies for how to manage interfaces; it leaves that
to a script, /etc/netplug.d/netplug, which is described in FILES below.
You tell netplugd which interfaces it should manage by giving it a list
of shell-style glob patterns, which it matches against using the
fnmatch(3) function. For example, a pattern of eth will tell
netplugd to only manage eth1 and eth3, if those interfaces exist. If the
interfaces are not known to the kernel at the time you start netplugd,
perhaps because they are unplugged PCMCIA network interfaces or devices
whose drivers have not yet been installed, netplugd will start to manage
them as soon as they are plugged in or their drivers are available.
-F Run in the foreground; do not detach and run as a daemon.
Messages are logged to stdout or stderr, instead of using the
syslog(3) mechanism. This option is useful mainly for debugging
-P Prevent autoprobing for interfaces. The netplugd 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 netplugd 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, netplugd will attempt to read from a
default config file. If you do not want netplugd to try to read
from any real config files, you can specify /dev/null as a config
Specify a pattern that will be used to match interface names that
netplugd should manage. You can provide this option multiple
times to specify multiple patterns.
Write the daemon's process ID to the file pid_file. If you tell
netplugd 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, e.g.
The "policy" program (typically a shell script) that netplugd
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
in 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
out 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
probe The command should load and initialise the driver for
this interface, if possible, and bring the interface into
the "up" state, so that it can generate netlink(7)
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.
The init(8) script that starts, stops, and displays status of the
netplugd was written by Bryan O'Sullivan <email@example.com>.
COPYRIGHT AND LICENSE
Copyright 2003 PathScale, Inc. Copyright 2003, 2004, 2005 Bryan
netplugd 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.
netplugd 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
cardmgr(5), hotplug(8), ip(8), netlink(7)