ANACRON(8) System Administration ANACRON(8)
NAME
anacron - runs commands periodically
SYNOPSIS
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]
DESCRIPTION
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). Spec-
ifying 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 immedi-
ately.
Unless Anacron is run with the -s or -n options, it starts jobs immedi-
ately 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 stan-
dard error, the output is mailed to the user under whom Anacron is run-
ning (usually root), or to the address specified in the MAILTO environ-
ment variable in the /etc/anacrontab file, if such exists. If the LOG-
NAME 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.
OPTIONS
-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.
SIGNALS
After receiving a SIGUSR1 signal, Anacron waits for any running jobs to
finish and then exits. This can be used to stop Anacron cleanly.
NOTES
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/zone-
info/localtime file. See tzset(3) for more information.
Timestamp files are created in the spool directory for each job speci-
fied 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.
FILES
/etc/anacrontab
Contains specifications of jobs. See anacrontab(5) for a com-
plete 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 lots of active jobs. See echo
$(($(ulimit -n) / 2)) for information how many concurent jobs anacron
may run.
Mail comments, suggestions and bug reports to Sean 'Shaleh' Perry
<shaleh@(debian.org|valinux.com)>.
AUTHOR
Anacron was originally conceived and implemented by Christian Schwarz
<schwarz AT monet.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 Malaova <mmaslano@redhat.
com>.
cronie 2012-11-22 ANACRON(8)
Linux-Distributionen
Huschi als Linux-Admin