cron(1M)							      cron(1M)

NAME    [Toc]    [Back]

     cron - clock daemon

SYNOPSIS    [Toc]    [Back]

     cron [ -j jobs ] [	nofork ]

DESCRIPTION    [Toc]    [Back]

     cron executes commands at specified dates and times.  Regularly scheduled
     commands can be specified according to instructions found in crontab
     files in the directory /var/spool/cron/crontabs.  Users can submit	their
     own crontab file via the crontab(1) command.  Commands that are to	be
     executed only once	can be submitted using the at(1) command.

     The following options are supported:

     -j	jobs   Specify the maximum number of jobs (MAXRUN) that	cron can
	       simultaneously run.  The	default	value is 25.  The maximum
	       allowed value is	250.

     nofork    If this option is supplied, cron	runs in	the foreground.

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

     Since cron	never exits, it	should be executed only	once.  This is done
     routinely through /etc/rc2.d/S75cron at system boot time.
     /etc/cron.d/FIFO is used as a lock	file to	prevent	the execution of more
     than one cron and is also used by the crontab command for notification of
     changes to	the crontab files.

     If	MAXRUN jobs are	running	and another is scheduled, cron does not	run
     the new job.  A message is	logged via syslog(3C).

     cron attempts to handle changes to	the system date	correctly, either
     forward or	backward.  There may be	some delay for jobs scheduled during
     the interval on large forward-time	changes.

     For each job launched, cron reads in configuration	information from
     /etc/default/cron.	Currently the only option supported is the
     SVR4_SIGNALS option, which	may be set to `YES' or `NO' (it	defaults to
     NO).  Setting SVR4_SIGNALS	to `YES' will result in	processes forked with
     the SIGXFSZ and SIGXCPU signals ignored.  For CPU and filesize resource
     limiting to work correctly, SVR4_SIGNALS should be	set to `NO', so	that
     these signal retain their default behaviour, which	is to terminate	the
     process.

FILES    [Toc]    [Back]

     /etc/cron.d		main cron directory





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cron(1M)							      cron(1M)



     /etc/cron.d/FIFO		used as	a lock file against multiple copies
				running	and also for notification of new or
				changed	crontab	files
     /var/cron/log		accounting information
     /var/spool/cron		spool area
     /etc/config/cron.options	site-dependent options /etc/default/cron
				default	behaviour configuration	file

SIGNALS    [Toc]    [Back]

     A SIGHUP signal can be sent to cron to cause it to	reexamine all the
     crontab and configuration files.  A message is logged for this event.
     The SIGTERM signal	should be used to shut cron down cleanly.

SEE ALSO    [Toc]    [Back]

     at(1), crontab(1),	sh(1).

DIAGNOSTICS    [Toc]    [Back]

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


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