Start shell script on Network Manager successful connection

24 Replies

The other day I was writing a script that needed to do its job only when specific network interface is triggered (wireless broadband ppp0 in my case). Pinging Google every 10 seconds to detect Internet access was out of the question. There is a more elegant way to do this. If you are interested please proceed.

Do you know that authors of Network Manager built option to trigger scripts right into this great application. To use this option you need to write bash script with some specific bash variables and put it to "/etc/NetworkManager/dispatcher.d/" directory. Specific variables are necessary to receive instructions from Network Manager about network interface that triggers execution of your script and should it be executed on "up" or "down" operation on that interface.

The following example script starts "command1" after ppp0 goes "up", "command2" just before ppp0 goes "down", "command3" just before ppp0 is "up", and "command4" just after ppp0 goes "down". Replace commands with what you want to accomplish, you can leave some of the command "fields" blank if you're not interested in some use cases like "pre-up" or "post-down".

#!/bin/bash
 
IF=$1
STATUS=$2
 
if [ "$IF" == "ppp0" ]
then
    case "$2" in
        up)
        logger -s "NM Script up triggered"
        command1
        ;;
        down)
        logger -s "NM Script down triggered"
        command2
        ;;
        pre-up)
        logger -s "NM Script pre-up triggered"
        command3
        ;;
        post-down)
        logger -s "NM Script post-down triggered"
        command4
        ;;
        *)
        ;;
    esac
fi

HERE you can download tarball with bash script used as an example (you need to modify it for whatever you want to trigger using Network Manager connections). Save it to your desktop and use this command to extract it:

tar -xjvf  /home/$USER/Desktop/90myscriptname.sh.tar.bz2 -C /home/$USER/Desktop/

This "90" in the name of the script means that this script will be executed in the last 10% of all scripts if you have a bunch of scripts to execute when your interface starts. You probably don't have any other scrips in "/etc/NetworkManager/dispatcher.d/" directory but this option is here if you need it. Now we should give permission to execute by doing "chmod +x" on our script and copy it in place.

chmod +x /home/$USER/Desktop/90myscriptname.sh
sudo cp /home/$USER/Desktop/90myscriptname.sh /etc/NetworkManager/dispatcher.d/90myscriptname.sh

Finally we will monitor "/var/log/syslog" as it changes to make sure that everything is in order:

sudo tail -f /var/log/syslog

If everything is OK you will see "NM Script action triggered" when you connect or disconnect network interface in question. If not, retrace your steps and double check everything. You can also ask here for my assistance and I will do my best to help you. That's it. Enjoy!

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24 thoughts on “Start shell script on Network Manager successful connection”

ignacio May 15, 2011 at 16:05:18

Hi,

I want to use you script to mount and unmount a network drive.

The unmount part works perfectly but the mount does not work 🙁

This is my script
#!/bin/bash

IF=$1
STATUS=$2

if [ “$IF” == “eth1” ]
then
case “$2” in
up)
logger -s “NM Script up triggered”
mount /home/ignacio/homedir
;;
down)
logger -s “NM Script down triggered”
fusermount -u /home/ignacio/homedir/
;;
esac
fi

And this is the line of the network drive in my fstab
sshfs#im5j@blue.unix.virginia.edu:/home/im5j /home/ignacio/homedir fuse fsname=sshfs#im5j@blue.unix.virginia.edu:/home/im5j,user,noauto,reconnect,transform_symlinks,BatchMode=yes 0 0

Any idea of what I’m doing wrong?

Thanks!

-Ignacio

Reply ↓
Marko Martinović AuthorMay 15, 2011 at 16:17:17

@ignacio

Hi Ignacio. Is your mount command working from terminal when you use it?

Reply ↓
ignacio May 15, 2011 at 16:36:05

@Marko Martinović
Yep, if I run it in the terminal works without a problem :-s

Reply ↓
ignacio May 15, 2011 at 16:57:00

@ignacio
I figured out the problem and i have an idea of how to solve it.

The script is trying to mount as root. I need to tell it to do it as the user ignacio.
Any idea how to do that

Best,

-Ignacio

Reply ↓
Marko Martinović AuthorMay 15, 2011 at 18:09:35

@ignacio

You can do that by using sudo. You run your command as another user like this sudo -u username command. Let me know if it works 🙂 Here’s the link for more info:

http://www.wlug.org.nz/SudoHowto

Reply ↓
ignacio May 15, 2011 at 18:19:54

@Marko Martinović
🙁
Nope, that is not the solution to my problem…
When i try to do it from the terminal (as root) it does not work

root@ignacio-Laptop:/home/ignacio# sudo -u ignacio /home/ignacio/scripts/homedir.sh
read: Connection reset by peer

Reply ↓
1. Marko Martinović AuthorMay 15, 2011 at 18:37:30
  
  Try this reading this, look at “user” option in the example. It is word “user” in the example not username or something (I know it is unintuitive 🙂 )…
  
  http://linux4research.blogspot.com/2007/08/fstab-and-user-permission.html
  
  You should modify fstab in a way that every user (including root) can mount you file system.
  
  Reply ↓
ignacio May 15, 2011 at 19:12:11

@Marko Martinović
I can mount it as root but if I do that I can not read it as Ignacio :_(

root@ignacio-Laptop:/home/ignacio# mount /home/ignacio/homedir/
root@ignacio-Laptop:/home/ignacio# cd homedir/
root@ignacio-Laptop:/home/ignacio/homedir# exit
ignacio@ignacio-Laptop:~$ ls
ls: cannot access homedir: Permission denied

any idea on how to fix that?

Thanks a lot!

Reply ↓
Marko Martinović AuthorMay 15, 2011 at 20:17:38

@ignacio

You need to give “user” param inside fstab like in the example.

“user – Permit any user to mount the filesystem. This automatically implies noexec, nosuid,nodev unless overridden.”

“Any” should include root and any other user. Did you try that? 🙂

Reply ↓
ignacio May 15, 2011 at 22:51:28

@Marko Martinović
I had user in my fstab from the begining 🙁

sshfs#im5j@blue.unix.virginia.edu:/home/im5j /home/ignacio/homedir fuse fsname=sshfs#im5j@blue.unix.virginia.edu:/home/im5j,user,uid=1000,gid=1000,umask=007,noauto,reconnect,transform_symlinks,BatchMode=yes 0 0

I can mount as root or ignacio but if i mount as root i can not access the folder as ignacio. Your script mount as root 🙁

Reply ↓
Marko Martinović AuthorMay 22, 2011 at 21:29:27

Ignacio found solution to this problem but at the time comments weren’t working because of TechyTalk.info hoster security settings (problem is resolved). Here’s the mail from Ignacio with the solution to his problem:

I have it working.
The script that is going to mount and umount is the following

#!/bin/bash
#/etc/NetworkManager/dispatcher.d/homedir

IF=$1
STATUS=$2

if [ “$IF” == “eth1” ]
then
case “$2” in
up)
logger -s “NM Script up triggered”
mount /home/ignacio/homedir/
;;
down)
logger -s “NM Script down triggered”
fusermount -u /home/ignacio/homedir/
;;
*)
;;
esac
fi

In /etc/fstab i have

sshfs#im5j@blue.unix.virginia.edu:/home/im5j /home/ignacio/homedir
fuse
fsname=sshfs#im5j@blue.unix.virginia.edu:/home/im5j,user,uid=1000,gid=1000,allow_other,umask=007,comment=sshfs,noauto,reconnect,BatchMode=yes
0 0

and finally in /etc/fuse.conf
user_allow_other

Thanks a lot for the help!!!

-Ignacio

Reply ↓
nicola October 31, 2011 at 10:51:19

Thank you very much Marko!
I’ve tried your instruction and all seems work.
I’ve a question: how can I run a script, not when interface is up, but when certain connection of an interface is up? (e.g. not when wlan0 is up, but when wireless connection “pippo-wifi”, that it is one of many connection that use wlan0, is up?)
Another time,
thanks,
Nicola

Reply ↓
1. Dana October 31, 2011 at 18:54:07
  
  Hello. man NetworkManager says that “Each script receives two arguments, the first being the interface name of the device just activated, and second an action.” So I guess no you can’t use this method to detect connection only interfaces, I might be wrong.
  
  Reply ↓
2. Dana October 31, 2011 at 18:57:49
  
  Correction, it also says “CONNECTION_UUID contains the UUID of the connection.” Thats something to explore…
  
  Reply ↓
Ball November 16, 2011 at 13:47:37

Unfortunately, NetworkManager seems forever crippled as pre-up isn’t implemented and seems will never be. It’s been an issue raised since 2007, so it’s a safe bet it’ll never be fixed because no-one can agree how to implement it. What a mess.

That means anyone who needs pre-up can’t use NetworkManager and must instead manually set up everything like a slave. Of course, wifi devices have to be setup for each situation, which is why NetworkManager was created, which I can’t use, ’cause it’s forever broken…..ahh linux

Reply ↓
1. Marko AuthorNovember 17, 2011 at 22:10:20
  
  True what you say but alternatives to Linux have even more “sell your soul to the devil” type of downsides so I guess we will stick to Linux 🙂 Also we can implement the functionality our selves it looks nice on the job application to say you’ve contributed to such major Linux app 😉
  
  Reply ↓
leili December 27, 2011 at 14:27:24

dear marko
I follow all your instruction but not anything happens!
It doesn’t work
why?
I just want to add sum route when an interface become up
please help me..

Reply ↓
Saeid May 10, 2012 at 08:01:34

If you want to use this script for VPN connections, you should change status value:
“up” -> vpn-up
“down” -> vpn-down

Reply ↓
1. Mike January 19, 2013 at 04:05:08
  
  Seconding this… for me, at least, not only SHOULD you change it, but you MUST change it to vpn-up / vpn-down. It took me a while to figure this out.
  
  Reply ↓
koogee November 29, 2012 at 14:20:53

Thanks mate!

Reply ↓
Roxo May 17, 2016 at 16:11:27

This post is old but still holds.

I was using it without any problem in [Xu|U]buntu 14.04. In 16.04 the “if” clause never got a True, so the “case” were never executed. The problem seems to be in the “if” clause. In order to check for equality one must use “=” and not “==” as published. Curiously the script worked until the upgrade.

HTH

Reply ↓
Tony April 26, 2017 at 22:08:49

Thanks for this. Solved my problem nicely.

Trivial query on the script:
you collect the value of $2:
STATUS=$2

but in the ‘case’ statement you use $2:
case "$2" in
rather than:
case "$STATUS" in

Is there a technical reason for this, or just a bad hair day? 🙂

Reply ↓
1. Marko AuthorApril 26, 2017 at 22:18:18
  
  Happy this helps! To answer your question, it was a bad hair day.
  
  Reply ↓
smartmeister July 10, 2017 at 01:26:59

Hi guys.

Network-manager seem to execute pre-up commands nicely in ubuntu-mate 17.04.

I wanted to enable WOL support as a pre-up command on my enp1s0 network interface, so that the computer is in the correct wol awareness state when i shut it down later.

All i had to do is create /etc/NetworkManager/dispatcher.d/pre-up.d/10wol.sh and fill it with the following command:

#!/bin/bash /sbin/ethtool -s enp1s0 wol g

and make it executable.
sudo chmod +x /etc/NetworkManager/dispatcher.d/pre-up.d/10wol.sh

i know it’s working as expected because ethtool show that the interface is set to “Wake-on: g” after a successfull pre-up command, otherwise it would stay as “Wake-on: d”, with is the default unconfigured state.

Reply ↓