The cron daemon checks the etccrontab file the

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The cron daemon checks the /etc/crontab file, the /etc/cron.d/ directory, and the /var/spool/cron/ directory every minute for any changes. If any changes are found, they are loaded into memory. Thus, the daemon does not need to be restarted if a crontab file is changed. Controlling Access to Cron The /etc/cron.allow and /etc/cron.deny files are used to restrict access to cron. The format of both access control files is one username on each line. Whitespace is not permitted in either file. The cron daemon ( crond ) does not have to be restarted if the access control files are modified. The access control files are read each time a user tries to add or delete a cron task. The root user can always use cron, regardless of the usernames listed in the access control files. If the file cron.allow exists, only users listed in it are allowed to use cron, and the cron.deny file is ignored. If cron.allow does not exist, users listed in cron.deny are not allowed to use cron.
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Starting and Stopping the Service To start the cron service, use the command /sbin/service crond start . To stop the service, use the command /sbin/service crond stop . It is recommended that you start the service at boot time. Refer to Chapter 15, Controlling Access to Services for details on starting the cron service automatically at boot
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