cron(1M)                                                           cron(1M)

NAME
     cron - clock daemon

SYNOPSIS
     /usr/sbin/cron

DESCRIPTION
     The cron command starts a process that executes commands at specified
     dates and times. Regularly scheduled commands can be specified accord-
     ing to instructions found in crontab files in the
     /var/spool/cron/crontabs directory. Users can submit their own crontab
     file via the crontab command. Commands which are to be executed only
     once may be submitted via the at(1) command.

     cron only examines crontab files and at command files during process
     initialization and when a file changes via the crontab or at commands.
     This reduces the overhead of checking for new or changed files at reg-
     ularly scheduled intervals.

     Since cron never exits, it should be executed only once. This is done
     routinely through /etc/rc2.d/S75cron when the system boots.
     /etc/cron.d/FIFO is used as a lock file to prevent more than one cron
     being executed.

     To keep a log of all actions taken by cron, CRONLOG=YES (by default)
     must be specified in the /etc/default/cron file. If CRONLOG=NO is
     specified, no logging is performed. Keeping the log is a user confi-
     gurable option since cron usually creates huge log files.

     To specify the maximum number of executable jobs, configure MAXRUN=25
     (default) to a value between 25 and 5120 in the /etc/default/cron
     file.

NOTES
     cron takes account of the changeover from winter time to summer time,
     i.e. cron recognizes the change of time and reinitializes when the
     changeover takes place.

     Correct recognition of the changeover from winter to summer time and
     vice versa means that when the clock is put back, cron routines are
     executed twice, and when the clock is put forward, cron routines are
     skipped. Therefore, if possible, no cron routines should be entered at
     the time when the clock is being put forward or back.

     If values from the /etc/default/cron file are changed while the system
     is running, these changed values only take effect once cron is res-
     tarted [see rc2(1M)].








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cron(1M)                                                           cron(1M)

DIAGNOSTICS
     A history of all actions taken by cron are recorded in /var/cron/log.

LOCALE
     The LCMESSAGES environment variable governs the language in which
     message texts are displayed.

     The LCTIME environment variable governs the format of date and time
     strings.

     If LCMESSAGES or LCTIME is undefined or is defined as the null
     string, it defaults to the value of LANG. If LANG is likewise unde-
     fined or null, the system acts as if it were not internationalized.

     If any of the locale variables has an invalid value, the system acts
     as if none of the variables was set.

     The LCALL environment variable governs the entire locale. LCALL
     takes precedence over all the other environment variables which affect
     internationalization.

FILES
     /etc/cron.d
          main cron directory

     /etc/default/cron
          used to enable/disable the logfile

     /etc/cron.d/FIFO
          used as a lock file

     /var/cron/log
          accounting information

     /var/spool/cron
          spool area

SEE ALSO
     at(1), crontab(1), sh(1), cron(4).















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