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CRON(8)			    System Manager's Manual		       CRON(8)

NAME
       cron - clock daemon

SYNOPSIS
       /usr/etc/cron

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

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

       Since  cron never exits,	it should only be executed once.  This is nor-
       mally done by running cron from the initialization process through  the
       file  /etc/rc;  see  init(8).  /var/spool/cron/FIFO is a	FIFO file that
       crontab and at use to communicate with cron; it is also used as a  lock
       file to prevent the execution of	more than one cron.

FILES
       /var/spool/cron		main cron directory
       /var/spool/cron/FIFO	FIFO for sending messages to cron
       /var/spool/cron/crontabs	directory containing crontab files

SEE ALSO
       at(1), crontab(1), sh(1), queuedefs(5), init(8),	syslogd(8)

DIAGNOSTICS
       cron  logs  various errors to the system	log daemon, syslogd(8),	with a
       facility	code of	cron.  The messages are	listed here, grouped by	sever-
       ity level.

   Err Severity
       Can't create /var/spool/cron/FIFO: reason
	      cron  was	 unable	 to  start  up	because	 it  could  not	create
	      /var/spool/cron/FIFO.

       Can't access /var/spool/cron/FIFO: reason
	      cron was	unable	to  start  up  because	it  could  not	access
	      /var/spool/cron/FIFO.

       Can't open /var/spool/cron/FIFO:	reason
	      cron   was  unable  to  start  up	 because  it  could  not  open
	      /var/spool/cron/FIFO.

       Can't start cron	- another cron may  be	running	 (/var/spool/cron/FIFO
       exists)
	      cron found that /var/spool/cron/FIFO already existed when	it was
	      started; this normally means that	cron had already been started,
	      but it may mean that an earlier cron terminated abnormally with-
	      out removing /var/spool/cron/FIFO.

       Can't stat /var/spool/cron/FIFO:	reason
	      cron could not get the status of /var/spool/cron/FIFO.

       Can't change directory to directory:reason
	      cron could not change to directory.

       Can't read directory:reason
	      cron could not read directory.

       error reading message: reason
	      An error occurred	when cron tried	to read	a control message from
	      /var/spool/cron/FIFO.

       message received	-- bad format
	      A	   message    was    successfully    read    by	   cron	  from
	      /var/spool/cron/FIFO, but	the message was	not of a  form	recog-
	      nized by cron.

       SIGTERM
	      received	cron  was told to terminate by having a	SIGTERM	signal
	      sent to it.

       cron could not unlink /var/spool/cron/FIFO: reason
	      cron was	told  to  terminate,  but  it  was  unable  to	unlink
	      /var/spool/cron/FIFO before it terminated.

       ******* CRON ABORTED ********
	      cron  terminated,	 either	due to an error	or because it was told
	      to.

       Can't open queuedefs file file:reason
	      cron could not open a queuedefs file.

       I/O error reading queuedefs file	file:reason
	      An I/O error occurred while cron was reading a queuedefs file.

       Using default queue definitions
	      An error occurred	while trying to	read a queuedefs file; the de-
	      fault queue definitions will be used.

       Can't allocate numberbytes of space
	      An internal error	occurred in cron while trying to allocate mem-
	      ory.

   Info	Severity
       queue queue max run limit reached
	      There were more jobs running or to be run	 in  the  queue	 queue
	      than  the	maximum	number specified.  cron	will wait until	one of
	      the currently-running jobs completes before starting  to	run  a
	      new one.

       MAXRUN (25) procs reached
	      There were more than 25 jobs running or to be run	by cron.  cron
	      will wait	until one of the currently-running jobs	completes  be-
	      fore starting to run a new one.

       *** cron	started	***
	      cron started running.

       >  CMD:	pid queue command job
	      A	 cron  job  was	 started, in queue queue, with process ID pid.
	      command is the command to	be run.	 For at	or batch jobs, job  is
	      the job number.

       > user pid queue	time job
	      A	 cron  job  was	 started  for  user user, in queue queue, with
	      process ID pid, at the date and time  time.   For	 at  or	 batch
	      jobs, job	is the job number.

       < user pid queue	time job status
	      A	cron job completed for user user, in queue queue, with process
	      ID pid, at the date and time time.  For at or batch jobs,	job is
	      the  job number.	If the command terminated with a non-zero exit
	      status or	a signal, status indicates the exit status or signal.

   Notice Severity
       Can't fork
	      An attempt to fork (2) to	run a new job failed;  cron  will  at-
	      tempt again after	a 30-second delay.

   Warning Severity
       Can't stat queuedefs file file:reason
	      cron  could  not	get the	status of a queuedefs file in order to
	      determine	whether	it has	changed.   cron	 will  assume  it  has
	      changed and will reread it.

				6 December 1988			       CRON(8)

NAME | SYNOPSIS | DESCRIPTION | FILES | SEE ALSO | DIAGNOSTICS

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