CRON(1M)                             SysV                             CRON(1M)



NAME
     cron - clock server

SYNOPSIS
     /etc/cron

DESCRIPTION
     cron executes commands at specified dates and times.  Regularly scheduled
     commands can be specified according to instructions found in crontab
     files in the directory /usr/spool/cron/crontabs.  You can submit your own
     crontab file via the crontab(1) command.  Commands to be executed only
     once can be submitted by using the at(1) command.

     cron only examines crontab files and at command files 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/rc at system boot time.  /usr/lib/cron/FIFO is
     used as a lock file to prevent the execution of more than one cron.

     /usr/lib/cron/FIFO may not be removed if the previous cron process did
     not clean up normally.  In this case, the FIFO file is still present.
     cron fails with a message that the FIFO exists.  Usually, this message
     warns you that cron is already running, but in this case, you need to
     remove the FIFO manually.

NOTE
     On Apollo systems, the directories /usr/lib/cron and /usr/spool/cron are
     both links to the `node_data/cron directory.  This separates each node's
     cron area into per-node directories.

FILES
     A history of all actions taken by cron are recorded in /usr/lib/cron/log.

SEE ALSO
     at(1), crontab(1), sh(1)