Removing CRONTAB jobs

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I've just set up a firewall for some students, now it's late and i'm still awake and ....   this machine is making a lot of noise. Are there any crontab jobs i surely should NOT remove ?   I've got crontabs for   ipac ipac-ng (both will be removed)   calendard find (noisy) logrotate man-db modutils netkit-inetd ntp-simple samba standard sysklogd   man2html wwwcount   scrollkeeper standard     Anyone with some good advise on this ?     Regards,   Joris