cron(1M) MISC. REFERENCE MANUAL PAGES cron(1M)
NAME
cron - clock daemon
SYNOPSIS
/usr/sbin/cron
DESCRIPTION
The cron command starts a process that 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 command. Com-
mands which are to be executed only once may be submitted
via the at command.
cron only examines crontab files and at command files during
process initialization and when a file changes via the cron-
tab or at commands. 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 /sbin/rc2.d/S75cron at system
boot time. /usr/lib/cron/FIFO is used as a lock file to
prevent the execution of more than one cron.
To keep a log of all actions taken by cron, CRONLOG=YES (by
default) must be specified in the /etc/default/cron file.
If CRONLOG=NO is specified, no logging is done. Keeping the
log is a user configurable option since cron usually creates
huge log files.
FILES
/usr/lib/cron main cron directory
/etc/default/cronused to maintain a log
/usr/lib/cron/FIFO
used as a lock file
/usr/spool/cron/log
accounting information
/var/spool/cron spool area
SEE ALSO
at(1), crontab(1), sh(1) in the User's Reference Manual.
DIAGNOSTICS
A history of all actions taken by cron are recorded in
/usr/spool/cron/log.
Last change: Essential Utilities 1