Creating a Cronjob to Run a Script Periodically

Ensure that crond.service is active and enabled:

systemctl status crond.service

If we see an active (running) status, then everything is good to go.

Check permissions on /usr/local/bin/loadavg.sh:

ls -l /usr/local/bin/loadavg.sh

Make it executable:

chmod a+x /usr/local/bin/loadavg.sh

Run the script:

/usr/local/bin/loadavg.sh

Check to see if the script sent data to /var/log/loadavg.log:

cat /var/log/loadavg.log

We should see a timestamp and the three load averages in there.

Use crontab -e to create the following content:

# Min   Hour    DoM     Month     DoW     Command
   *    8-17     *        *       1-5     /usr/local/bin/loadavg.sh

Save the cronjob and check our work:

crontab -l

Again, we could verify crond.service is running using systemctl. If we want to know whether our job is running or not, we can run tail /var/log/cron after a few minutes, and we should see entries in there for our loadavg.sh script. We should also take a look at the log that the script is writing to, with:

systemctl status crond.service
tail /var/log/cron
cat /var/log/loadavg.log

If the job is running, then we'll see contents like we did when we ran the script manually, once a minute.