Ubuntu Manpage: anacron - runs commands periodically

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 command.

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 timestamp 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 background 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 completely 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 priority 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 executed 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 accomplished 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.

DEBIAN-SPECIFIC CONFIGURATION

       On Debian-based systems, anacron will be activated hourly every day from 07:30 local  time
       to  23:30  local time through cron job (on non-systemd systems where cron is installed and
       enabled) or systemd timer (on systemd-based systems).  On activation, anacron  will  check
       if it missed some jobs. If yes, it will start those jobs after a short period of time.

       By  default, The hourly activation of anacron will not take place when the system is using
       battery and no AC power is connected to the computer. It is meant to  reduce  power  usage
       and  extend  battery  life,  but  such  design  might lead to unwanted results.  Users may
       disable this feature and let anacron run regardless of power supply. Please  read  Debian-
       specific   documentation   in   /usr/share/doc/anacron/README.Debian   file  for  detailed
       instruction in now to change such behaviour.

FILES

       /etc/anacrontab
              Contains specifications of jobs.  See anacrontab(5) for a complete description.

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

       /lib/systemd/system/anacron.service
              This file provides systemd service for anacron.

       /lib/systemd/system/anacron.timer
              This file provides systemd timer for anacron. Currently the  service  is  triggered
              hourly through systemd timer.

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)>.
       During  2004-2006,  it  was maintained by Pascal Hakim <pasc@(debian.org|redellipse.net)>.
       During 2009-2014, it was maintained by Peter Eisentraut <petere@debian.org>.

       Nowadays anacron in Debian is co-maintained by various developers from Debian Project.