Mac OS X is underpinned by BSD UN*X; this means that Mac users, system administrators and developers all have access to a wide range of tools conventionally associated with UN*X systems.

One of the more useful utility programs found on most UN*X boxes is the cron daemon, which allows a user to schedule repeating tasks; unfortunately, whilst Mac OS X has a perfectly good cron daemon, it doesn't perform any tasks when the machine is asleep or switched-off. Moreover, cron won't go back and process tasks it has missed, which means that the early-morning cleanup tasks configured by Apple are next to useless for many people.

Fortunately, this problem has existed for some time on other platforms, hence the existence of anacron, which is designed to run tasks that it has missed (for example because the machine is asleep).

Here is a Mac OS X disk image containing all the files you need; after installing the package within this disk image, you should find that anacron has taken-over processing of all the periodic cleanup tasks on your Mac.

N.B. This version of the Anacron package is not compatible with Mac OS X 10.4. Please see Ronald Florence's site for a package compatible with 10.4 (Tiger).

Uninstalling Anacron

Uninstalling anacron is fairly straightforward; you can deactivate it by:

1. Editing /etc/crontab to remove the last four lines, which should look like this:

   #
   # All of the periodic jobs that were controlled by cron are now controlled
   # by anacron.
   15	*	*	*	*	root	/usr/local/sbin/anacron -s
   

2. Uncommenting (i.e., remove the ‘#’ characters) the lines listed under “Run daily/weekly/monthly jobs”, again in /etc/crontab. After you're done, the lines in question should look like this:

   # Run daily/weekly/monthly jobs.
   15	3	*	*	*	root	periodic daily
   30	4	*	*	6	root	periodic weekly
   30	5	1	*	*	root	periodic monthly
   

If you want to remove it completely, follow the instructions for deactivating it, then delete the following files:

/Library/StartupItems/Anacron
/usr/local/sbin/anacron
/usr/local/share/man/man8/anacron.8
/usr/local/share/man/man5/anacrontab.5
/var/spool/anacron
/etc/anacrontab