How can I stop a systemd service with cron?

Question

I have a simple crontab entry that is supposed to stop a service, yet it does not work.

* * * * * systemctl stop nginx

I even tried:

* * * * * /bin/systemctl stop nginx

Since that't the location of systemctl that which command shows.

That line works with root user, yet not working with root's crontab.

And by not working, I mean the service is not shut down. I can confirm the server is still running and systemctl status nginx show it's active.

What am I doing wrong?

Solution

Probably because you haven't told cron to use root.

* * * * * root /bin/systemctl stop nginx

That will execute the command every minute, regardless of the nginx status (started or not)

So that being said, if the goal is to make sure nginx is never started, why not just disable it?

systemctl disable nginx

==Edit==

Good point made by Aaron Copley in the comments, in order to make sure nginx wont be started even after boot the command should be;

systemctl mask nginx

Comments

[guzzijason]

What do your cron logs say?

[Michael Hampton]

What was the output of systemctl status nginx?

[guzzijason]

This is not always true - if the entry is put into /etc/crontab or /etc/cron.d/*, then yes you will need to include the user in the crontab entry. However, if you add this job to root's individual crontab (such as /var/spool/cron/root, or crontab -e -u root) then there is no need to specify the user.

[Jimbotron]

That was just an example, I could have put 10 16 * * *, this was just to illustrate that the problem is not due to time not properly being set. The point is, I am creating crontab entry with root user and the service is not shutting down.

[Aaron Copley]

systemctl disable nginx will only prevent it from starting on boot and won't stop it from being started as a dependency of another service. You want systemctl mask nginx to prevent the service from being able to be started at all.