Crontab is used to schedule the command to run at a specific time on your system. For example, you may want to take a backup of your database, reboot your system, to run a script at a specific time. In this tutorial, I will show how to configure cronjob on your system. You can use this tutorial to configure on Ubuntu, Linux mint, centos, etc. I will also show you how to set up the different timings on crontab.
The crontab has a total of 6 fields. The first 5 field is for setting the timings and the last field is for setting the path of the script/commands.
Below is the picture that demonstrates what each field/asterisk (*) do.
Create or update crontab
To create or update crontab enter the following command.
The above command will open the crontab shell where you can edit or update the cronjob
List all the crontab
To list all the crontab entries use the following command
Below are the examples of crontab that you can use
|Cronjob timings||Cronjob Config||Cronjob Description|
|Every minute||* * * * *||Cronjob will run every minute|
|Every five minutes||*/5 * * * *||Cronjob will run every five minutes|
|Every Ten minutes||*/10 * * * *||Cronjob will run every ten minutes|
|Every Thirty minutes||*/30 * * * *||Cronjob will run every Thirty minutes|
|Every hour/hourly||0 * * * *||Cronjob will run every hour|
|Every day at 1:30||30 1 * * *||Cronjob will run every day at 1:30|
|Twice a day at 01 AM and 2 PM||00 01,13 * * *||Cronjob will run twice a day at 01 AM and 02 PM|
|Weekly on Monday||0 01 * * MON||Cronjob will run weekly on Monday at 01 AM|
|Every Year January||0 0 1 1 *||Cronjob will run every year on January 1 at 12:00 AM|
|Every month||0 01 1 * *||Cronjob will run every month at 01:00 AM|