How to set up Cron Job on Ubuntu 18.04

How to set up Cron Job on Ubuntu 18.04

Setting up a Cron job on Ubuntu 18.04

CronJob is a Linux task scheduler that schedules tasks at specific times and schedules tasks to repeat after a specific time. In this tutorial, you will learn how to set up a Cron job on Ubuntu.

Prerequisites

Before you start setting up a Cron job on Ubuntu 18.04. The server requires a non-root user account with sudo privileges.

Install Crontab

Ubuntu 18.04 server comes with crontab pre-installed, so you don’t need to install it manually. If you are working on the desktop, enter the following command:

Update the package manager index by entering

sudo apt update

Run the following command to install crontab

sudo apt install cron

Open crontab with text editor

To open crontab in a text editor, enter the following command

crontab -e

After entering the above command, you will be prompted to select a text editor. If you are editing for the first time, select or select nano. When you select a text editor, the following window opens.

Set crontab on Ubuntu Set up crontab on Ubuntu

After editing the file, simply exit and save using Ctrl+x And press y.

In the screenshot above, the meaning of the m h dom mon dow user header is as follows:

* m = the minute the cron job will run. (0-59) * h = an integer that determines the time to execute the task. (0-23) * dom = day on which the cron job will run. (1 to 31). * mon = month in which the cron job will run. (1 to 12) * day of week for dow = 0 to 6 (0 for Sunday). (0-6) * user = name of the user running cron. * command = Linux command to execute.

Asterisk (*) for crontab timing

Here, the asterisk (*) is widely used in cronjob settings. That is, if * is specified for m (minute), the command will be executed every minute.

Basic example of Cron job

Cron runs every minute

* * * * * [user] [command]

Cron running 10 minutes of time, such as 12:10, 01:10, 02:10

10 * * * * [user] [command]

Cron running 30 minutes of an hour, such as 12:30, 01:30, 02:30

30 * * * * [user] [command]

Cron executed every hour (when minute becomes zero)

0 * * * * [user] [command]

Kron running at midnight

0 0 * * * [user] [command]

Cron running at 8am

0 8 * * * [user] [command]

Cron to execute PHP scripts

 * * * * * root /usr/bin/php /var/www/html/project/test.php

Advanced cron examples

Using commas in crontab: The following command is executed on January 15, March, July and December 15 at 8:45 am

45 8 15 Jan,Mar,Jul,Dec * [user] [command]

If you use the division operator in crontab: If the minute is divided by 10, the following command will be executed every 0, 10, 20, 30, 40, 50 minutes (if the minute is divisible by 10).

*/5 * * * * [user] [command]

Crontab Dashesh: The next crontab runs every month from the 15th to the 20th. Dashes represent ranges.

0 0 15-20 * *[user] [command]

Conclusion

Here, you learned how to set up a Cron job on Ubuntu 18.04. If you have any questions about this, please comment below.

Sidebar