Using `cron` jobs allow us to run processes according to a recurring schedule. We can set them to run at set times at regular intervals, to perform functions like backups, send emails, or most anything else we might want to do, which can be very useful for a System Administrator.
Learning Objectives
Successfully complete this lab by achieving the following learning objectives:
- Verify That the crond Service Is Enabled and Running
Ensure that
crond.serviceis active and enabled:systemctl status crond.serviceIf we see an active (running) status, then everything is good to go.
- Verify that /usr/local/bin/loadavg.sh is Executable for All and Produces Correct Output
Check permissions on
/usr/local/bin/loadavg.sh:ls -l /usr/local/bin/loadavg.shMake it executable:
chmod a+x /usr/local/bin/loadavg.shRun the script:
/usr/local/bin/loadavg.shCheck to see if the script sent data to
/var/log/loadavg.log:cat /var/log/loadavg.logWe should see a timestamp and the three load averages in there.
- Create a cron Job that Executes /usr/local/bin/loadavg.sh Once per Minute During the Hours of 8AM-5PM on Monday through Friday
Use
crontab -eto create the following content:# Min Hour DoM Month DoW Command * 8-17 * * 1-5 /usr/local/bin/loadavg.shSave the cronjob and check our work:
crontab -l- Verify Cronjob is Running and Producing Correct Output
Again, we could verify
crond.serviceis running usingsystemctl. If we want to know whether our job is running or not, we can runtail /var/log/cronafter a few minutes, and we should see entries in there for ourloadavg.shscript. 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.logIf the job is running, then we’ll see contents like we did when we ran the script manually, once a minute.
