Hier kommt der Inhalt einer normalen /etc/crontab Datei:
# /etc/crontab: system-wide crontab
# Unlike any other crontab you don't have to run the `crontab'
# command to install the new version when you edit this file.
# This file also has a username field, that none of the other crontabs
# do.
SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
# m h dom mon dow user command
25 6 * * * root test -e /usr/sbin/anacron || run-parts --report
/etc/cron.daily
47 6 * * 7 root test -e /usr/sbin/anacron || run-parts --report
/etc/cron.weekly
52 6 1 * * root test -e /usr/sbin/anacron || run-parts --report
/etc/cron.monthly
#
Die Zeilenumbrüche musst Du natürlich noch korrigieren.