It’s quite easy. It’s also basically not findable on the web. Probably because a simple
# crond --help
crond: invalid option -- '-'
Usage:
crond [options]
Options:
-h print this message
-i deamon runs without inotify support
-m <comm> off, or specify prefered client for sending mails
-n run in foreground
-p permit any crontab
-P use PATH="/usr/bin:/bin"
-c enable clustering support
-s log into syslog instead of sending mails
-x <flag> print debug information
Debugging flags are: ext,sch,proc,pars,load,misc,test,bit
Provides the answer.