cron man page on DigitalUNIX

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cron(8)								       cron(8)

       cron - The system clock daemon


       The cron daemon runs shell commands at specified dates and times.  Com‐
       mands 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 exam‐
       ines 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  execution  without	a  login user ID set. It maintains the
       /usr/spool cron/atjobs and the /usr spool cron/crontabs spool direcito‐
       ries  as	 multilevel directories; 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
       profile	of the account associated with the login user ID of the invok‐
       ing process: 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  activi‐
       ties).  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)


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