‘Cron’ is a command whose services are initialized when the system is brought up in multiuser mode. When loaded, it executes commands at specified dates and times. It runs in background as a clock daemon until it is killed either by the ‘super’ user or when the system shuts down or ‘init’ed in a mode that kills it. The cron daemon wakes up once a minute to see if anything needs to be run. Heavily loaded systems many expect a delay of a few minutes.
These commands are specified in a specially formatted file in the ‘/usr/spool/cron/crontabs’ or ‘var/spool/cron/crontabs’ directory. The file that executes ‘super’ user commands can be found in the root file. Regular users may also submit jobs to ‘cron’ deamon as long as they have ‘cron’ permission.
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