anacron



ANACRON(8)                   Anacron Users’ Manual                  ANACRON(8)




NAME

       anacron - runs commands periodically


SYNOPSIS

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


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  times-
       tamp  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).

       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

       -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.


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  is  currently  maintained  by  Sean  ’Shaleh’  Perry
       <shaleh@(debian.org|valinux.com)>.



Sean ’Shaleh’ Perry               2000-06-22                        ANACRON(8)

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