Nethook is a daemon that runs scripts when network interfaces change state. I wrote nethook before I was aware of ifup-local and ifdown-local. You can probably use them instead.

When a network interface goes down, the following locations are checked for scripts. If they exist and are executable, they are run.

• /etc/nethook/ifup.d/*
• /etc/nethook/ifup-$DEVICE

Similarly, when a network interface goes up, the following locations are checked for scripts to run.

• /etc/nethook/ifdown.d/*
• /etc/nethook/ifdown-$DEVICE

Prior to running the scripts, nethook parses /etc/sysconfig/network-scripts/ifcfg-$DEVICE if it exists and makes the variables set in it available in the scripts' environment.

Nethook was tested on Red Hat Enterprise Linux 5, aka RHEL5, but it should work on any similar distributions which

• Place network interface configuration in /etc/sysconfig/network-scripts/ifcfg-*
• When NICs change state, signal processes that called netreport

Nethook requires the following Perl modules, which are available in the EPEL repository.

• perl-App-Daemon
• perl-IO-Interface
• perl-Log-Log4perl
• perl-YAML

$ git clone git://github.com/sciurus/nethook.git
$ mv nethook/nethook /usr/sbin/nethook
$ mv init/sysv /etc/init.d/nethook
$ chkconfig nethook on
$ service nethook start

As of version 0.13, App::Daemon's status command returns LSB-compliant exit codes. If you're using this version, the third step could be replaced by ln -s /usr/sbin/nethook /etc/init.d/nethook.