cron.roflcopter.fr is perfectly suited for monitoring cron jobs. All you have to do is update your cron job command to send a HTTP request to cron.roflcopter.fr after a job completes.
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 future, without
You can set up cron.roflcopter.fr to notify you whenever the backup script does not run on time or 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 epression 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 3 https://cron.roflcopter.fr/ping/your-uuid-here > /dev/null
Now, each time your cron job runs, it will send a HTTP request to the ping URL. Since cron.roflcopter.fr knows the schedule of your cron job, 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 tells curl to not print anything to standard output unless there is an error. Feel free to adjust the curl options to suit your needs.
|&&||Run curl only if
|-f, --fail||Makes curl treat non-200 responses as errors|
|-s, --silent||Silent or quiet mode. Don't show progress meter or error messages.|
|-S, --show-error||When used with -s it makes curl show error message if it fails.|
|--retry <num>||If a transient error is returned when curl tries to perform a transfer, it will retry this number of times before giving up. Setting the number to 0 makes curl do no retries (which is the default). Transient error means either: a timeout, an FTP 4xx response code or an HTTP 5xx response code.|
|> /dev/null||Redirect curl's stdout to /dev/null (error messages go to stderr,)|
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