anacron - runs commands periodically
anacron [-s] [-f] [-n] [-d] [-q]
] [ -S spooldir
anacron [-S spooldir] -u [-t anacrontab] [job] ...
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
When executed, Anacron reads a list of jobs from a configuration file, normally
). 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
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
matches any of the job
command-line arguments. The
arguments can be shell wildcard patterns (be sure to protect them
from your shell with adequate quoting). Specifying no job
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
options are given, Anacron starts jobs
immediately when their delay is over. The execution of different jobs is
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
"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.
- 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 -s.
- 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.
- Suppress messages to standard error. Only applicable with
- -t anacrontab
- 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.
- -S spooldir
- 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.
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.
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.
- Contains specifications of jobs. See anacrontab(5)
for a complete description.
- This directory is used by Anacron for storing timestamp
anacrontab(5), cron(8), tzset(3)
The Anacron README
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
Anacron was originally conceived and implemented by Christian Schwarz
The current 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