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.
Anacron is not an attempt to make cron redundant.
– A functioning syslog daemon.
– A functioning /usr/sbin/sendmail command. (all MTAs should have that).