Creating cronjob in ubuntu

Type : crontab -e

Then we can mention our command
# m h dom mon dow command

*/15 * * * * /deploy/project/cronjobs/alert.sh (Path file for where we have that sh file)

This will run for every 15 minute.

Example for run the rake task:
----------------------------------------------------

In the sh file we need to write the following details,
open the alert.sh and type the following

cd /home/deploy/applicationdirectory
/usr/bin/rake alerts

here this is the script for running the alerts tasks