how can I schedule a custom script to run whenever I restart a service

Question:

I wish to know how can I schedule a custom script to run whenever I restart a service.

My use case is that I have to run several commands whenever I restart my Tomcat Service. I want to know if there is a way I can write a script and schedule it to run whenever I restart the Tomcat service.I have setup the tomcat script as a systemd service. I am using Cent OS 7 x64.

Reply:

(you probably only need to replace httpd by tomcat everywhere).

Simply create an new systemd httpd.service file in /etc which includes and overrides part of the one in /lib. For example, create /etc/systemd/system/httpd.service to contain

.include /lib/systemd/system/httpd.service
[Service]
ExecStartPre=/home/meuh/myscripttorun  some pre args here
ExecStartPost=/home/meuh/myscripttorun some post args here

Any ExecStartPre lines will be executed before the apache ExecStart line, and similarly any ExecStartPost will run after apache has started.