Now I want to use Backup and Whenever gem to automatic backup my database.
When I connect the server by ssh as an added user to run backup perform -t my_backup,it works well.But the cron file:

0 22 * * * /bin/bash -l -c 'backup perform -t my_backup'

can't run at 22:00.
When I use cat /etc/crontab check the cron's config file,it is:

SHELL=/bin/sh

PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin



# m h dom mon dow user  command

17 *    * * *   root    cd / && run-parts --report /etc/cron.hourly

25 6    * * *   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )

47 6    * * 7   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )

52 6    1 * *   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.monthly )

#

The /bin/bash and /bin/sh are different.What's the reason?How to do?