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 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.
- -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.
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.
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.
- /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.
anacrontab(5),
cron(8),
tzset(3)
The Anacron
README file.
For Debian-specific modifications, please read
/usr/share/doc/anacron/README.Debian file for detailed information.
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)>.
Anacron was originally conceived and implemented by Christian Schwarz
<
[email protected]>. The current implementation is a complete
rewrite by Itai Tzur <
[email protected]>.
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 <
[email protected]>.
Nowadays anacron in Debian is co-maintained by various developers from Debian
Project.