runs commands periodically
[-s] [-f] [-n] [-d] [-q]
[-t anacrontab] [-S spooldir] [job] ...
anacron [-S spooldir] -u [-t anacrontab]
anacron -T [-t anacrontab]
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.
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
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.
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).
-d option is given (see below), Anacron forks to the
background when it starts, and the parent process exits
-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.
messages about what Anacron is doing are sent to
syslogd(8) under facility cron, priority
notice. Error messages are sent at priority
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
Force execution of the jobs,
ignoring the timestamps.
Only update the timestamps of the jobs, to the current
date, but don’t run anything.
Serialize execution of jobs. Anacron will not start a
new job before the previous one finished.
Run jobs now. Ignore the delay specifications in the
/etc/anacrontab file. This options implies
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
Suppress messages to standard error. Only applicable
Use specified anacrontab,
rather than the default
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.
Use the specified spooldir to
store timestamps in. This option is required for users who
wish to run anacron themselves.
Print version information, and exit.
Print short usage message, and exit.
a SIGUSR1 signal, Anacron waits for running jobs, if
any, to finish and then exits. This can be used to stop
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.
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
Contains specifications of
jobs. See anacrontab(5) for a complete
This directory is used by
Anacron for storing timestamp files.
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).
suggestions and bug reports to Sean ’Shaleh’
originally conceived and implemented by Christian Schwarz
implementation is a complete rewrite by Itai Tzur
The code base
was maintained by Sean ’Shaleh’ Perry
Since 2004, it
is maintained by Pascal Hakim