cron(8) - NetBSD Manual Pages

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


NAME

     cron -- daemon to execute scheduled commands (Vixie Cron)


SYNOPSIS

     cron [-x debugflags]


DESCRIPTION

     cron is normally started during system boot by rc.d(8) framework, if cron
     is switched on in rc.conf(5).

     cron searches /var/cron/tabs for crontab files which are named after
     accounts in /etc/passwd.  Crontabs found are loaded into memory.  cron
     also searches for /etc/crontab which is in a different format (see
     crontab(5)).  cron then wakes up every minute, examining all stored
     crontabs, checking each command to see if it should be run in the current
     minute.  When executing commands, any output is mailed to the owner of
     the crontab (or to the user named in the MAILTO environment variable in
     the crontab, if such exists).

     Events such as START and FINISH are recorded in the /var/log/cron log
     file with date and time details.  This information is useful for a number
     of reasons, such as determining the amount of time required to run a par-
     ticular job.  By default, root has an hourly job that rotates these log
     files with compression to preserve disk space.

     Additionally, cron checks each minute to see if its spool directory's
     modtime (or the modtime on /etc/crontab) has changed, and if it has, cron
     will then examine the modtime on all crontabs and reload those which have
     changed.  Thus cron need not be restarted whenever a crontab file is mod-
     ified.  Note that the crontab(1) command updates the modtime of the spool
     directory whenever it changes a crontab.

     The -x flag turns on some debugging flags.  debugflags is comma-separated
     list of debugging flags to turn on.  If a flag is turned on, cron writes
     some additional debugging information to system log during its work.
     Available debugging flags are:
     sch   scheduling
     proc  process control
     pars  parsing
     load  database loading
     misc  miscellaneous
     test  test mode - do not actually execute any commands
     bit   show how various bits are set (long)
     ext   print extended debugging information


FILES

     /var/cron/tabs  cron spool directory
     /etc/crontab    system crontab
     /var/log/cron   log file for cron events


SEE ALSO

     crontab(1), crontab(5)


AUTHORS

     Paul Vixie <paul@vix.com>

NetBSD 5.1                     December 29, 2007                    NetBSD 5.1