Run a script automatically when an IP is added

[Cameron Simpson]

On 26Aug2014 09:37, Yong Huang <yong321 at yahoo.com> wrote:
>Oracle's clusterware can migrate a VIP from one server to another. I'd like to have the target server automatically run a shell script once the new IP comes in. Is there a way to detect that and trigger execution of this script?
>
>This
>http://www.diglinux.com/2012/04/07/linux-heartbeat-ip-fail-over-2/
>looks like what I need. But I wonder if a simpler solution exists, preferably without installing extra package. In fact, yum install heartbeat on my Red Hat box didn't find the package.

Since nobody has replied, this is something you can do yourself with a little 
script. As a starting point, this lists all the IPv4 addresses on my host 
(current OSX, but adjusting for Linux "ifconfig" output should be easy):

   ifconfig -a | sed -n 's/^ inet \([1-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*\) .*/\1/p'

Note that the first whitespace before "inet" is a TAB character.

Have a look at "ifconfig -a" on your system and adjust the regexp.

(Or, if you care only about a specific interface, use "ifconfig eth0" or 
whatever to monitor just that interface.)

Then all you would do is run that, pipe it through "sort -u", and put the 
output in a file.

Next time, run it, sort, put in a temp file.

Compare them ("cmp -13 old-file tmp-file" should be useful) to get a list of 
new IP addresses. When you get a new one, do what you want. Save the tmp-file 
to the old-file for use on the next run.

Put it in cron to run regularly.

Cheers,
Cameron Simpson <cs at zip.com.au>

WFO: the normal throttle position for Denizens, squids, and unfortunates on
      50cc Honda step-throughs.