View Full Version : [all variants] Call shell script on network change

January 21st, 2011, 10:55 AM
I have a script that I would like to run when my laptops connects to a new network (e.g. changes to another SSID). I've done some searching on the net but could not find any suitable solution (but I bet there is). Can anyone give me a hint please?

January 21st, 2011, 11:20 AM
What have you done so far?

January 21st, 2011, 11:51 AM
Basically all I've done was searching on google as I am not a really experienced Linux user :>
What I found is e.g. that the NetworkManager sends a message on dBus but that would requite a programm to run permanently to check for them!?

Maybe I have not searched for the right keywords.

January 21st, 2011, 01:22 PM
Ok, I finally found something that looks like it could help.
(searching for 'interface' gave much better results)


It says that I have to copy the script to

# /etc/network/if-up.d/
and then edit

and append

post-up /etc/network/if-up.d/my_script.sh

und the eth0 configuration section (I hope for wlan0 to work too) but the problem is that the file does not contain anything abouth eth0 :[
It just looks like:

auto lo
iface lo inet loopback

So is the information on that webpage outdated? Or should I simply add auto eth0 and/or auto wlan0 ?

January 21st, 2011, 05:02 PM
If your interfaces file only contains these two lines, it means that network-manager is in charge of bringing your interfaces up. Why don't you use NM for the other interfaces (right click on the NM icon) ?

January 21st, 2011, 05:11 PM
With the Network Manager I cannot setup any script to be run if the interface goes up (or at least I was not able to find it).

January 21st, 2011, 07:08 PM
The Network Manager still runs the scripts under /etc/network/if-*.d/. You don't need to specify it in the /etc/network/interfaces file. (See /etc/NetworkManager/dispatcher.d/01ifupdown, which invokes run-parts.)

BTW, I just spent a bunch of time figuring out that a script named "my_script.sh" will not run - it must conform to a naming convention without a suffix and so must be called only "my_script".

Here's a sample script, which I call "iface_changed" (formerly iface_changed.sh). Put this somewhere and point symbolic links at it from all of the /etc/network/if-*.d/ directories. It just logs info into a temp file, so that you can see what happens during network state transitions.

# Do something for an interface state change.

# From interfaces(5) man page:
# All of these commands have access to the following environment vari‐
# ables.
# IFACE physical name of the interface being processed
# logical name of the interface being processed
# address family of the interface
# METHOD method of the interface (e.g., static)
# MODE start if run from ifup, stop if run from ifdown
# PHASE as per MODE, but with finer granularity, distinguishing the pre-
# up, post-up, pre-down and post-down phases.
# indicates whether --verbose was used; set to 1 if so, 0 if not.
# PATH the command search path: /usr/local/sbin:/usr/local/bin:‐
# /usr/sbin:/usr/bin:/sbin:/bin


echo "------------------" >> $OUT
date >> $OUT
echo "Physical Interface: $IFACE" >> $OUT
echo "Logical Interface: $LOGICAL" >> $OUT
echo "Phase: $PHASE" >> $OUT
echo "Mode: $MODE" >> $OUT
echo "------------------" >> $OUT

exit 0