anacron - runs commands periodically
SYNOPSIS
anacron [-s] [-f] [-n] [-d] [-q] [-t anacrontab] [job] ...
anacron -u [-t anacrontab] [job] ...
anacron [-V|-h]
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 config
uration 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 speci
fied 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 pat
terns (be sure to protect them from your shell with ade
quate quoting). Specifying no job arguments, is equiva
lent to specifying "*" (That is, all jobs will be consid
ered).
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
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 times
tamps.
-u Only update the timestamps of the jobs, to the cur
rent 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 stan
dard error, as well as to syslog. The output of
jobs is mailed as usual.
-q Suppress messages to standard error. Only applica
ble with -d.
-t anacrontab
Use specified anacrontab, rather than the default
-V Print version information, and exit.
-h Print short usage message, and exit.
SIGNALS
After receiving a SIGUSR1 signal, Anacron waits for run
ning 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.
FILES
Contains specifications of jobs. See anacrontab(5)
for a complete description.
/var/spool/anacron
This directory is used by Anacron for storing
timestamp files.
SEE ALSO
anacrontab(5), cron(8), tzset(3)
The Anacron README file.
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 Chris
tian Schwarz <schwarz@monet.m.isar.de>.
The current implementation is a complete rewrite by Itai
Tzur <itzur@actcom.co.il>.
The code base is currently maintained by Sean 'Shaleh'
Perry <shaleh@(debian.org|valinux.com)>.
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