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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | SIGNALS | NOTES | FILES | SEE ALSO | BUGS | AUTHOR | COLOPHON |
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ANACRON(8) System Administration ANACRON(8)
anacron - runs commands periodically
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]
Anacron is 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 are not running 24 hours a day to control regular
jobs as daily, weekly, and monthly jobs.
Anacron reads a list of jobs from the /etc/anacrontab
configuration file (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 time period specified for that
job. If a job has not been executed in n days or more, 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 (excludes the
hour) in a special timestamp file for that job, so it knows when
to execute that job again.
When there are no more jobs to be run, Anacron exits.
Anacron only considers jobs whose identifier, as specified in
anacrontab(5), matches any of the job command-line arguments. The
job command-line arguments can be represented by shell wildcard
patterns (be sure to protect them from your shell with adequate
quoting). Specifying no job command-line arguments is equivalent
to specifying "*" (that is, all jobs are considered by Anacron).
Unless Anacron is run with the -d option (specified below), it
forks to the background when it starts, and any parent processes
exit immediately.
Unless Anacron is run with the -s or -n options, it starts jobs
immediately when their delay is over. The execution of different
jobs is completely independent.
If an executed job generates any output to standard output or to
standard error, the output is mailed to the user under whom
Anacron is running (usually root), or to the address specified in
the MAILTO environment variable in the /etc/anacrontab file, if
such exists. If the LOGNAME environment variable is set, it is
used in the From: field of the mail.
Any informative messages generated by Anacron are sent to
syslogd(8) or rsyslogd(8) under with facility set to cron and
priority set to notice. Any error messages are sent with the
priority error.
"Active" jobs (i.e., jobs that Anacron already decided to run and
are now waiting for their delay to pass, and jobs that are
currently being executed by Anacron), are "locked", so that other
copies of Anacron cannot run them at the same time.
-f Forces execution of all jobs, ignoring any timestamps.
-u Updates the timestamps of all jobs to the current date, but
does not run any.
-s Serializes execution of jobs. Anacron does not start a new
job before the previous one finished.
-n Runs jobs immediately and ignores the specified delays in
the /etc/anacrontab file. This options implies -s.
-d Does not fork Anacron to the background. In this mode,
Anacron will output informational messages to standard
error, as well as to syslog. The output of any job is
mailed by Anacron.
-q Suppresses any messages to standard error. Only applicable
with -d.
-t some_anacrontab
Uses the specified anacrontab, rather than the
/etc/anacrontab default one.
-T Anacrontab testing. Tests the /etc/anacrontab configuration
file for validity. If there is an error in the file, it is
shown on the standard output and Anacron returns the value
of 1. Valid anacrontabs return the value of 0.
-S spooldir
Uses the specified spooldir to store timestamps in. This
option is required for users who wish to run anacron
themselves.
-V Prints version information, and exits.
-h Prints short usage message, and exits.
After receiving a SIGUSR1 signal, Anacron waits for any running
jobs to finish and then exits. This can be used to stop Anacron
cleanly.
Make sure your time-zone is set correctly before Anacron is
started since 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
specified in an anacrontab. These files are never removed
automatically by Anacron, and should be removed by hand if a job
is no longer being scheduled.
/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.
anacrontab(5), cron(8), tzset(3)
The Anacron README file.
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 lots of active jobs. See
echo $(($(ulimit -n) / 2)) for information how many concurrent
jobs anacron may run.
Mail comments, suggestions and bug reports to Sean 'Shaleh' Perry
⟨shaleh@(debian.org|valinux.com)⟩.
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|
redellipse.net)⟩.
For Fedora, Anacron is maintained by Marcela Mašláňová
⟨mmaslano@redhat.com⟩.
This page is part of the cronie (crond daemon) project.
Information about the project can be found at
⟨https://github.com/cronie-crond/cronie⟩. If you have a bug report
for this manual page, see
⟨https://github.com/cronie-crond/cronie/issues⟩. This page was
obtained from the project's upstream Git repository
⟨https://github.com/cronie-crond/cronie.git⟩ on 2025-08-11. (At
that time, the date of the most recent commit that was found in
the repository was 2025-07-31.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
cronie 2012-11-22 ANACRON(8)
Pages that refer to this page: cronnext(1), anacrontab(5)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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