close

Using Crontab on CentOS: Step-by-Step Guide

Crontab is a utility on the CentOS operating system that allows you to schedule recurring tasks at a predetermined time. Here are instructions for using crontab on CentOS:

Step 1: Open crontab for the current user

To open crontab for the current user, run the following command:

crontab -e

Step 2: Understand the crontab syntax

Each line in the crontab represents a specific scheduled task.

The crontab syntax is as follows:

* * * * * command_to_be_executed
- - - - -
| | | | |
| | | | ----- Day of the week (0 - 7) (Sunday is 0 and 7)
| | | ------- Month (1 - 12)
| | --------- Day of the month (1 - 31)
| ----------- Hour (0 - 23)
------------- Minute (0 - 59)

The asterisk (*) means all possible values for that field.

Step 3: Define tasks in the crontab

For example, to run a script named "myscript.sh" at 1 AM every day, add the following line to the crontab:

0 1 * * * /path/to/myscript.sh

Step 4: Save and exit

After adding tasks to the crontab, save and exit by pressing Ctrl + X, then type Y and press Enter.

Step 5: View crontab

To view the list of tasks in the crontab, run the following command:

crontab -l

Step 6: Remove a task from the crontab

o remove a task from the crontab, run the following command:

crontab -r

Note: Be careful when using crontab, ensure the syntax and scheduling time are correct to avoid system malfunction or overload.