The command crontab for managing user Cron configurations was not found

webmin ->system->Scheduled Cron Jobs

The command crontab for managing user Cron configurations was not found. Maybe Cron is not installed on this system?

[root@ns1 ~]# crobtab -e

-bash: crobtab: command not found

[root@ns1 ~]# chmod 2755 /usr/bin/crontab

chmod: cannot access `/usr/bin/crontab': No such file or directory

[root@ns1 ~]# crontab -l

-bash: crontab: command not found

[root@ns1 ~]# crontab -e

-bash: crontab: command not found

[root@ns1 ~]# which crontab

/usr/bin/which: no crontab in (/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin)

I have virtualmin & webmin installed in centos 6 34 bit dedicated server (installed using install.sh script).

Please suggest. Thanks