Step 5: Create a Cron Job
=========================

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.. contents:: Table of Contents

**Objective**: Create a ``cron job`` for your backup script.

Now that you have a simple backup script, you want to run it periodically
to ensure that your data is copied to another part of your VPS to keep it
safe from accidental deletion.

Use |A Beginners Guide To Cron Jobs| and |Creating a custom Cron Job|
to help you.


Build a Daily Cron Job
----------------------
You will use the ``crontab`` application to install, remove, or edit
cron jobs.

#. Edit the cron jobs.
#. Choose a time to run the script.

   * You should perform the backup when the system has low usage,
     such as when most of your users sleep.

   * Pick a time between 02:00 to 05:00.

#. Build your cron job. This example runs at 03:00 daily.

   .. code-block:: bash

       0 3 * * * <command-to-execute>

#. List the cron jobs to verify that they were installed correctly.

   .. code-block:: bash

       crontab -l

Testing your Cron Job
---------------------
It is not easy to test cron jobs that run infrequently. You need to know
two things: |br| **(1)** Did it run, and **(2)** did it run correctly.

* You can run a cron job manually using Webmin: |br|
  *Webmin* -> *System* -> *Scheduled Cron Jobs*

* The output will display to the browser.

Another method is to log the output data to a file instead of to the screen.
You can use this information to determine if it ran and if it produced
expected data.

* You can configure a command to send |standard output| (stdout) results
  to a file instead of the screen using ``> output-file``:

  .. code-block:: bash

      command > /path/to/output.txt

  .. code-block:: bash
      :caption: Examples

      # shell commands
      ls -lh > dir-listing.txt
      ./backup-docker.sh > /tmp/output.txt

      # from a cron job
      0 3 * * * bash /root/backup-user-data.sh > /var/user-backups/backup-log.txt