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+anacron (periodic command scheduler)
+
+anacron is a periodic command scheduler. It executes commands at
+intervals specified in days. Unlike cron, it does not assume that the
+system is running continuously. It can therefore be used to control
+the execution of daily, weekly and monthly jobs (or anything with a
+period of n days), on systems that don't run 24 hours a day. When
+installed and configured properly, Anacron will make sure that the
+commands are run at the specified intervals as closely as
+machine-uptime permits.
+
+Every time Anacron is run, it reads a configuration file that
+specifies the jobs Anacron controls, and their periods in days. If a
+job wasn't executed in the last n days, where n is the period of that
+job, Anacron executes it. Anacron then records the date in a special
+timestamp file that it keeps for each job, so it can know when to run
+it again. When all the executed commands terminate, Anacron exits.
+
+It is recommended to run Anacron from the system boot-scripts. For
+example, add the following lines to /etc/rc.d/rc.local:
+
+ if [ -x /usr/sbin/anacron -a -f /etc/anacrontab ]; then
+ /usr/sbin/anacron -s > /dev/null 2>&1
+ fi
+
+This way the jobs "whose time has come" will be run shortly after the
+machine boots. A delay can be specified for each job so that the
+machine isn't overloaded at boot time.
+
+In addition to running Anacron from the boot-scripts, it is also
+recommended to schedule it as a daily cron-job (usually at an early
+morning hour), so that if the machine is kept running for a night,
+jobs for the next day will still be executed.
+
+See anacron (8), anacrontab (5) and /usr/doc/anacron-2.3/README
+for further information.