anacron man page on ElementaryOS

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ANACRON(8)		     Anacron Users' Manual		    ANACRON(8)

NAME
       anacron - runs commands periodically

SYNOPSIS
       anacron	[-s]  [-f]  [-n] [-d] [-q] [-t anacrontab] [-S spooldir] [job]
       ...
       anacron [-S spooldir] -u [-t anacrontab] [job] ...
       anacron [-V|-h]
       anacron -T [-t anacrontab]

DESCRIPTION
       Anacron can be used to execute commands periodically, with a  frequency
       specified in days.  Unlike cron(8), it does not assume that the machine
       is running continuously.	 Hence, it can be used on machines that aren't
       running 24 hours a day, to control daily, weekly, and monthly jobs that
       are usually controlled by cron.

       When executed, Anacron reads a list of jobs from a configuration	 file,
       normally	 /etc/anacrontab  (see anacrontab(5)).	This file contains the
       list of jobs that Anacron controls.  Each job entry specifies a	period
       in  days, a delay in minutes, a unique job identifier, and a shell com‐
       mand.

       For each job, Anacron checks whether this job has been executed in  the
       last  n	days,  where  n is the period specified for that job.  If not,
       Anacron runs the job's shell command, after waiting for the  number  of
       minutes specified as the delay parameter.

       After  the  command  exits, Anacron records the date in a special time‐
       stamp file for that job, so it can know when to execute it again.  Only
       the date is used for the time calculations.  The hour is not used.

       When there are no more jobs to be run, Anacron exits.

       Anacron	only  considers	 jobs  whose  identifier,  as specified in the
       anacrontab matches any of the  job  command-line	 arguments.   The  job
       arguments  can be shell wildcard patterns (be sure to protect them from
       your shell with adequate quoting).  Specifying  no  job	arguments,  is
       equivalent to specifying "*"  (That is, all jobs will be considered).

       Unless  the  -d option is given (see below), Anacron forks to the back‐
       ground when it starts, and the parent process exits immediately.

       Unless the -s or -n options are given, Anacron starts jobs  immediately
       when  their  delay  is  over.   The execution of different jobs is com‐
       pletely independent.

       If a job generates any output on its standard output or standard error,
       the  output is mailed to the user running Anacron (usually root), or to
       the address  contained  by  the	MAILTO	environment  variable  in  the
       crontab, if such exists.

       Informative messages about what Anacron is doing are sent to syslogd(8)
       under facility cron, priority notice.  Error messages are sent at  pri‐
       ority error.

       "Active"	 jobs  (i.e.  jobs that Anacron already decided to run and now
       wait for their delay to pass, and jobs that are	currently  being  exe‐
       cuted  by Anacron), are "locked", so that other copies of Anacron won't
       run them at the same time.

OPTIONS
       -f     Force execution of the jobs, ignoring the timestamps.

       -u     Only update the timestamps of the jobs, to the current date, but
	      don't run anything.

       -s     Serialize	 execution  of jobs.  Anacron will not start a new job
	      before the previous one finished.

       -n     Run  jobs	 now.	Ignore	the  delay   specifications   in   the
	      /etc/anacrontab file.  This options implies -s.

       -d     Don't fork to the background.  In this mode, Anacron will output
	      informational messages to standard error, as well as to  syslog.
	      The output of jobs is mailed as usual.

       -q     Suppress messages to standard error.  Only applicable with -d.

       -t anacrontab
	      Use specified anacrontab, rather than the default

       -T     Anacrontab  testing.  The	 configuration file will be tested for
	      validity. If there is an error in the file,  an  error  will  be
	      shown  and  anacron will return 1. Valid anacrontabs will return
	      0.

       -S spooldir
	      Use the specified spooldir to store timestamps in.  This	option
	      is required for users who wish to run anacron themselves.

       -V     Print version information, and exit.

       -h     Print short usage message, and exit.

SIGNALS
       After  receiving	 a  SIGUSR1 signal, Anacron waits for running jobs, if
       any, to finish and then exits.	This  can  be  used  to	 stop  Anacron
       cleanly.

NOTES
       Make  sure  that	 the  time-zone	 is  set  correctly  before Anacron is
       started.	 (The time-zone affects the date).   This  is  usually	accom‐
       plished	by  setting  the  TZ  environment variable, or by installing a
       /usr/lib/zoneinfo/localtime file.  See tzset(3) for more information.

       Timestamp files are created in the spool	 directory  for	 each  job  in
       anacrontab.  These  are	never  removed	automatically  by anacron, and
       should be removed by hand if a job is no longer being scheduled.

FILES
       /etc/anacrontab
	      Contains specifications of jobs.	See anacrontab(5) for  a  com‐
	      plete description.

       /var/spool/anacron
	      This directory is used by Anacron for storing timestamp files.

SEE ALSO
       anacrontab(5), cron(8), tzset(3)

       The Anacron README file.

BUGS
       Anacron never removes timestamp files.  Remove unused files manually.

       Anacron	uses  up  to two file descriptors for each active job.	It may
       run out of descriptors if there are more than about 125 active jobs (on
       normal kernels).

       Mail  comments,	suggestions  and  bug  reports	to Sean 'Shaleh' Perry
       <shaleh@(debian.org|valinux.com)>.

AUTHOR
       Anacron was originally conceived and implemented by  Christian  Schwarz
       <schwarz@monet.m.isar.de>.

       The   current  implementation  is  a  complete  rewrite	by  Itai  Tzur
       <itzur@actcom.co.il>.

       The   code   base   was	 maintained    by    Sean    'Shaleh'	 Perry
       <shaleh@(debian.org|valinux.com)>.

       Since  2004,  it is maintained by Pascal Hakim <pasc@(debian.org|redel‐
       lipse.net)>.

Pascal Hakim			  2004-07-11			    ANACRON(8)
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