Category: Linux Terminal
Added: 20th of October 2020
Updated On: 1st of April 2023
Viewed: 2,147 times
Create a simple cronjob in Linux
In Linux you can automate tasks by creating a cronjobs. This can be especially helpful if for example you wanted to created a backup of your database everyday, calling a bash or .php script.
Getting your head around Cronjobs can be confusing at the start, so I will attempt to explain how they work with some really simple examples.
There are two parts to a cronjob. The first part is telling the system when you want to run the cron job, and the second part is telling the system what you want it to do using linux commands.
Part 1: Telling the system when to run your cronjob
This is set out using the following parameters
m=Minute
h=Hour
dom=Day of Month
mon=Month
dow=Day of Week
Run a cronjob at 10am on the 25th of December
Run a cronjob at 10:10am on the 25th of December
Run a cronjob at 10:10am on the 25 of Every Month
Run a cronjob at 10:10am every day of the year
Run a cronjob every minute, of every day, all year
Part 2: Telling the system what to do
In this part you set your command. To keep things really simple we copy an image from the Pictures folder to the Desktop.
When we put it all together we get the following cron statement.
At 10:00am on the 25th December copy tux.png from the Pictures folder to Desktop
How to set the cron job
To create a working cron job open your terminal and enter the following command.
Please note: You might want to set the time and date nearer to your own times and dates so you can see the cronjob in action.
You will notice the terminal will open with nano editor. Enter the information below the commented out section. Remember to replace username with your own username
Once you have entered the information, do the following
1) Press CTRL + o to save, and then press enter to confirm
2) Press CTRL + x to exit nano
Your cronjob has now been saved.
To view the cronjob you just created, open your terminal and enter the following command
If you have set the times and date nearer to your own time and date, the cronjob should now be ready to go.
This is a just a very basic example and only covers a small part of cron, but is enough to give you a starting point.
If you visit https://crontab.guru/ you can try different cron schedule expressions