When I schedule a job, some seem to be applied immediately, while others after a reboot. So is it recommended to restart cron (crond) after adding a new cron job? How to do that properly (esp. in a Debian system), and should that be done with sudo (like sudo service cron restart) even for that of normal users'?I tried:/etc/init.d/cron restartwhich doesn't seem to work (neither does /etc/init.d/cron stop or service cron stop) and completes with return code 1.Here's a part of the message output:Since the script you are attempting to invoke has been converted to an  Upstart job, you may also use the stop(8) utility, e.g. stop cron  stop: Rejected send message, 1 matched rules; type=method_call, sender=:1.91 (uid=1000 pid=3647 comm=stop cron ) interface=com.ubuntu.Upstart0_6.Job member=Stop error name=(unset)  requested_reply=0 destination=com.ubuntu.Upstart (uid=0 pid=1 comm=/sbin/init)(what does that mean?)
Is a restart of cron or crond necessary after each new schedule addition or modification?
cron
No you don't have to restart cron, it will notice the changes to your crontab files (either /etc/crontab or  a users crontab file).At the top of your /etc/crontab you probably have (if you have the Vixie implementation of cron that IIRC is the one on Debian):# /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# and files in /etc/cron.d. These files also have username fields,# that none of the other crontabs do.The reason you might not see specific changes implemented is if you add things to e.g. /etc/cron.daily and the daily run has already occurred. The message that you get is because you use an old way of restarting cron on your system. The recommended way (but not necessary if you just edit cron files) is: restart cronYou of course have to reboot in order to see the effects of a @reboot cron job