System Settings/Task Scheduler
Task Scheduler is a graphical front end to the standard "cron" utility. With it, commands (or "tasks") can be run at specific times, on a certain day or date, or at specific intervals (time between execution).
Task Scheduler can be started by starting the System Settings application. Selectfollwed by .
Adding and Modifying tasks
- Click to add a new task, or "Modify" to modify an existing task. The Add or modify existing task page will be displayed.
- Enter the command to be run. Click the folder icon to choose it from a dialog.
- Enter a comment (optional). This should be descriptive, explaining what the task will do as the command may not always be obvious.
- Click Enable this task to enable the task to run.
- Click Run at system bootup to enable the script to run each time the system is booted.
- Click Run every day to enable the script to run every day. This will automatically select the appropriate options.
- Using the buttons, choose when the command should be run. Not all parameters are required, those not needed may be left blank.
- Hours and Minutes are the time of day to run the task, not an interval.
- When done, click . The task will be added and scheduled if enabled.
Removing a task
To completely remove a task, select the task from the list and click the Delete button. This will permanently remove the task.
Sometimes a task or multiple tasks need a specific variable set, it must be added in the Environment Variables section. The cron utility uses its own environment, system-wide and user-specific variables are not used. Click New Variable to add a new variable definition, or Modify to change an existing variable.
- Enter the name of the variable to use. This name:
- Must consist of letters, digits, and underscore ('_') only
- Must start with a letter
- Should not be a reserved or commonly used system variable. See https://pubs.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap08.html for more information
- The value the variable will contain. This can be a number or string.
- Enter a brief description of the variable.
- All the files that are modified are located in the /etc/cron directory where there are numerous files to look at.
- The command-line tool that allows you to have a look at the currently installed cron-jobs is
crontab -l(that's the letter L).