Every service must be set to either be "On" (enabled) or "Off" (disabled) for every runlevel.

 To see what services are enabled for each runlevel, run:

         # /sbin/chkconfig --list

 To control which services are enabled for a runlevel, run system-config-services in the GUI or ntsysv at the command line. (Previous Fedora releases may have serviceconf instead of system-config-services).

 To manually enable a specific service use chkconfig. The following command turns crond daemon for both runlevel 3 *AND* 5.

 
        # /sbin/chkconfig --level 35 crond on

 
The --level could be 1, 2, 3, 4, 5 or any combination of the numbers. The on option can also be off. Running man chkconfig is useful.