130 lines
3.3 KiB
Groff
130 lines
3.3 KiB
Groff
.\" $NetBSD: cron.8,v 1.8 2007/12/29 13:21:57 wiz Exp $
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.\"
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.\"/* Copyright 1988,1990,1993 by Paul Vixie
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.\" * All rights reserved
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.\" *
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.\" * Distribute freely, except: don't remove my name from the source or
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.\" * documentation (don't take credit for my work), mark your changes (don't
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.\" * get me blamed for your possible bugs), don't alter or remove this
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.\" * notice. May be sold if buildable source is provided to buyer. No
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.\" * warrantee of any kind, express or implied, is included with this
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.\" * software; use at your own risk, responsibility for damages (if any) to
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.\" * anyone resulting from the use of this software rests entirely with the
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.\" * user.
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.\" *
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.\" * Send bug reports, bug fixes, enhancements, requests, flames, etc., and
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.\" * I'll try to keep a version up to date. I can be reached as follows:
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.\" * Paul Vixie <paul@vix.com> uunet!decwrl!vixie!paul
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.\" */
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.\"
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.\" Id: cron.8,v 2.2 1993/12/28 08:34:43 vixie Exp
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.\"
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.Dd December 29, 2007
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.Dt CRON 8
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.Os
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.Sh NAME
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.Nm cron
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.Nd daemon to execute scheduled commands (Vixie Cron)
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.Sh SYNOPSIS
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.Nm
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.Op Fl x Ar debugflags
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.Sh DESCRIPTION
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.Nm
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is normally started during system boot by
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.Xr rc.d 8
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framework, if cron is switched on in
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.Xr rc.conf 5 .
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.Pp
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.Nm
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searches
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.Pa /var/cron/tabs
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for crontab files which are named after accounts in
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.Pa /etc/passwd .
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Crontabs found are loaded into memory.
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.Nm
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also searches for
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.Pa /etc/crontab
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which is in a different format (see
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.Xr crontab 5 ) .
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.Nm
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then wakes up every minute, examining all stored crontabs, checking each
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command to see if it should be run in the current minute.
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When executing commands, any output is mailed to the owner of the
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crontab (or to the user named in the
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.Ev MAILTO
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environment variable in the crontab, if such exists).
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.Pp
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Events such as
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.Dv START
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and
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.Dv FINISH
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are recorded in the
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.Pa /var/log/cron
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log file with date and time details.
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This information is useful for a number of reasons, such as
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determining the amount of time required to run a particular job.
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By default, root has an hourly job that rotates these log files
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with compression to preserve disk space.
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.Pp
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Additionally,
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.Nm
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checks each minute to see if its spool directory's modtime (or the modtime
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on
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.Pa /etc/crontab )
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has changed, and if it has,
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.Nm
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will then examine the modtime on all crontabs and reload those which have
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changed.
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Thus
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.Nm
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need not be restarted whenever a crontab file is modified.
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Note that the
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.Xr crontab 1
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command updates the modtime of the spool directory whenever it changes a
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crontab.
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.Pp
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The
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.Fl x
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flag turns on some debugging flags.
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.Ar debugflags
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is comma-separated list of debugging flags to turn on.
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If a flag is turned on,
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.Nm
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writes some additional debugging information to system log during
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its work.
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Available debugging flags are:
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.Bl -tag -width proc -compact
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.It Ar sch
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scheduling
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.It Ar proc
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process control
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.It Ar pars
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parsing
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.It Ar load
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database loading
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.It Ar misc
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miscellaneous
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.It Ar test
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test mode - do not actually execute any commands
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.It Ar bit
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show how various bits are set (long)
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.It Ar ext
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print extended debugging information
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.El
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.Sh FILES
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.Bl -tag -width /var/cron/tabs -compact
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.It Pa /var/cron/tabs
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.Nm
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spool directory
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.It Pa /etc/crontab
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system crontab
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.It Pa /var/log/cron
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log file for cron events
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.El
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.Sh SEE ALSO
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.Xr crontab 1 ,
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.Xr crontab 5
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.Sh AUTHORS
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.An Paul Vixie
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.Aq paul@vix.com
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