cron.roflcopter.fr is perfectly suited for monitoring cron jobs. All you have to do is update your cron job command to send an HTTP request to cron.roflcopter.fr after completing the job.
Let's look at an example:
$ crontab -l # m h dom mon dow command 8 6 * * * /home/user/backup.sh
The above job runs
/home/user/backup.sh every day at 6:08. The backup
script is presumably a headless, background process. Even if it works
correctly currently, it can start silently failing in the future without
You can set up cron.roflcopter.fr to notify you whenever the backup script does not run on time, or it does not complete successfully. Here are the steps to do that.
If you have not already, sign up for a free cron.roflcopter.fr account.
In your cron.roflcopter.fr account, add a new check.
Give the check a meaningful name. Good naming will become increasingly important as you add more checks to your account.
Edit the check's schedule:
8 6 * * *in the cron expression field
Take note of your check's unique ping URL.
Finally, edit your cron job definition and append a curl or wget call after the command:
$ crontab -e # m h dom mon dow command 8 6 * * * /home/user/backup.sh && curl -fsS --retry 5 -o /dev/null https://cron.roflcopter.fr/ping/your-uuid-here
Now, each time your cron job runs, it will send an HTTP request to the ping URL. Since cron.roflcopter.fr knows your cron job's schedule, it can calculate the dates and times when the job should run. As soon as your cron job doesn't report at an expected time, cron.roflcopter.fr will send you a notification.
This monitoring technique takes care of various failure scenarios that could potentially go unnoticed otherwise:
The extra options in the above example tell curl to retry failed HTTP requests, and silence output unless there is an error. Feel free to adjust the curl options to suit your needs.
/home/user/backup.shexits with an exit code 0.
If your cron job consistently pings cron.roflcopter.fr an hour early or an hour late, the likely cause is a timezone mismatch: your machine may be using a timezone different from what you have configured on cron.roflcopter.fr.
On modern GNU/Linux systems, you can look up the time zone using the
timedatectl status command and looking for "Time zone" in its output:
$ timedatectl status Local time: C 2020-01-23 12:35:50 EET Universal time: C 2020-01-23 10:35:50 UTC RTC time: C 2020-01-23 10:35:50 Time zone: Europe/Riga (EET, +0200) System clock synchronized: yes NTP service: active RTC in local TZ: no
On a systemd-based system, you can use the
journalctl utility to see system logs,
including logs from the cron daemon.
To see live logs:
To see the logs from e.g. the last hour, and only from the cron daemon:
journalctl --since "1 hour ago" -t CRON