Network Manager: Execute Script on Network Change

Execute a script when network changes is rather easy with systemd (if you use the right services).

Network Manager

Assuming you are using NetworkManager (default on Gnome):

systemctl enable NetworkManager-dispatcher
systemctl start NetworkManager-dispatcher

The man page tells you to install a script in one of:

ls -la /etc/NetworkManager/dispatcher.d/
total 20
drwxr-xr-x 5 root root 4096 Feb  3 19:02 .
drwxr-xr-x 7 root root 4096 Apr 20 18:43 ..
drwxr-xr-x 2 root root 4096 Jul 13  2022 no-wait.d
drwxr-xr-x 2 root root 4096 Jul 13  2022 pre-down.d
drwxr-xr-x 2 root root 4096 Jul 19 16:21 pre-up.d

The script can use special variables with information about the connection parameters.

Example Script. The script monitor changes and execute commands before connecting to a given Wifi. It has to be stored in /etc/NetworkManager/dispatcher.d/pre-up.d/

#+begin_example bash #!/bin/sh

if [ “$2” = “pre-up” ]; then if [ “$CONNECTION_ID” = “MyWifi” ]; then

else

fi fi #+end_src

The documentation can also be found here.

Networkd

(Never tried myself)

The Arch documentation suggests to install and use networkd-dispatcher.

The reference can be found here, in the “Tips and tricks” section.