Scheduling tasks with Cron
Cron is a tool for configuring scheduled tasks on Unix systems. It is used to schedule commands or scripts to run periodically and at fixed intervals. Tasks range from backing up the user's home folders every day at midnight, to logging CPU information every hour.
crontab (cron table) is used to edit the list of scheduled tasks in operation, and is done on a per-user basis; each user (including
root) has their own
A graphical application for Cron is available by installing the
sudo apt-get install gnome-schedule
You can then launch the program Scheduled Tasks from the main menu.
crontab with the
-e flag to edit the cron table:
Select an editor
The first time you run
crontab you'll be prompted to select an editor; if you are not sure which one to use, choose
nano by pressing
Add a scheduled task
The layout for a cron entry is made up of six components: minute, hour, day of month, month of year, day of week, and the command to be executed.
# m h dom mon dow command
# * * * * * command to execute # ┬ ┬ ┬ ┬ ┬ # │ │ │ │ │ # │ │ │ │ │ # │ │ │ │ └───── day of week (0 - 7) (0 to 6 are Sunday to Saturday, or use names; 7 is Sunday, the same as 0) # │ │ │ └────────── month (1 - 12) # │ │ └─────────────── day of month (1 - 31) # │ └──────────────────── hour (0 - 23) # └───────────────────────── min (0 - 59)
0 0 * * * /home/pi/backup.sh
This cron entry would run the
backup.sh script every day at midnight.
View scheduled tasks
View your currently saved scheduled tasks with:
Run a task on reboot
To run a command every time the Raspberry Pi starts up, write
@reboot instead of the time and date. For example:
@reboot python /home/pi/myscript.py
This will run your Python script every time the Raspberry Pi reboots. If you want your command to be run in the background while the Raspberry Pi continues starting up, add a space and
& at the end of the line, like this:
@reboot python /home/pi/myscript.py &