Monday, December 07, 2009

IP Conflict Detection on Ubuntu

One thing that drives me crazy as a consultant is going to sites and acquiring a duplicate IP.  Windows tells you there is a conflict.  Ubuntu does not unless you install some additional software - IPwatchD.

There are 2 ways to install IPwatchD.  Passive mode or active mode.  Passive mode just logs packets, active mode uses Gratuitous Arp and notifies you of a problem.

The notification works nicely in 9.10 (as shown).

Here are the steps I followed:

I will add some additional info.

The article doesn't say what to do to get the script to run at setup.  It's simple.  In 9.10 there is a file  you can update to run scripts as root after user login.  They are nice enough to provide a sample.

# Note: this is a sample and will not be run as is.  Change the name of this
# file to /PostLogin/Default for this script to be run.  This
# script will be run before any setup is run on behalf of the user and is
# useful if you for example need to do some setup to create a home directory
# for the user or something like that.  $HOME, $LOGIN and such will all be
# set appropriately and this script is run as root.

If you don't already use the file, copy the sample it to its final destination and add the login script for IPwatchD:

sudo cp /etc/gdm/PostLogin/Default.sample /etc/gdm/PostLogin/Default
echo /usr/local/sbin/ipwatchd -c /usr/local/etc/ipwatchd.conf | sudo tee -a /etc/gdm/PostLogin/Default

logout and back in or reboot to check the work.

Show running status:

ps aux | grep ipwatchd
You'll see something like:

mikem@mikem-9751L:~$ ps aux | grep ipwatchd 
root     28581  0.0  0.1  12388  4744 ?        Ss   21:58   0:00 /usr/local/sbin/ipwatchd -c /usr/local/etc/ipwatchd.conf
mikem    30234  0.0  0.0   7340   892 pts/0    S+   22:15   0:00 grep ipwatchd

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