crontab -l (pour chaque user) OU ls /var/spool/cron/crontabs/*

cat /etc/crontab

for file in $(ls /etc/cron.d); do echo $file && cat $file; done

for file in $(ls /etc/cron.hourly); do echo $file && cat $file; done
for file in $(ls /etc/cron.daily); do echo $file && cat $file; done
for file in $(ls /etc/cron.weekly); do echo $file && cat $file; done
for file in $(ls /etc/cron.monthly); do echo $file && cat $file; done