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cron(8)								      cron(8)


  cron - The system clock daemon




  The cron daemon runs shell commands at specified dates and times.  Commands
  that are to run according to a regular or periodic schedule are found
  within the crontab files. Commands that are to run once only are found
  within the at	files.	You submit crontab and at file entries by using	the
  crontab and at commands.  Because the	cron process exits only	when killed
  or when the system stops, only one cron daemon should	exist on the system
  at any given time.  Normally,	you start the cron daemon from within a	run
  command file.


       Other that logging a startup entry in the /var/adm/cron/log file, the
       cron daemon does	not log	its activities.	 You can use the Event
       Manager (EVM) to	create custom events for tasks that are	scheduled by
       the cron	daemon.	See EVM(5) for more information.

  During process initialization	and when cron detects a	change,	it examines
  the crontab and at files. This strategy reduces the overhead of checking
  for new or changed files at regularly	scheduled intervals. The cron daemon
  must be started from the system startup scripts because it must begin	exe-
  cution without a login user ID set. It maintains the /usr/spool cron/atjobs
  and the /usr spool cron/crontabs spool direcitories as multilevel direc-
  tories; jobs and crontabs submitted reside in	the directory associated with
  the sensitivity level	of the process that invoked at or crontab. It uses
  the level of the subdirectory	as the one at which to start the job.  The
  cron communication FIFO is graded at the System High sensitivity level. The
  cron daemon starts each job with the following process attributes stored
  with the job by the invoking process:

    +  Login user ID

    +  Effective and real user IDs

    +  Effective and real group	IDs

    +  Supplementary groups

    +  Sensitivity level

    +  Information label

  It also establishes the following attributes from the	authentication pro-
  file of the account associated with the login	user ID	of the invoking

    +  Audit control and disposition masks

    +  Clearance

    +  Kernel authorizations

    +  Base privilege set


  The at and batch programs will refuse	to accept jobs submitted from
  processes whose login	user ID	is different from the real user	ID.


      Specifies	the command path.

      Main cron	directory

      Directory	containing the crontab files.

      List of allowed users.

      List of denied users

      This file	contains startup information. (It is not a log of cron

      Queue description	file for at, batch, and	cron


  Commands: at(1), crontab(1), rc0(8), rc2(8), rc3(8)

  Files: queuedefs(4)

  Misc:	EVM(5)