Lee, Thanks so much, this is VERY informative, it also is a pleasure to hear someone of intelligence speak (type). I'll see about upgrading MacJanitor.
John R. On Jan 13, 2006, at 9:14 AM, Lee Larson wrote: > Yesterday I wrote that Apple has changed the way they do the > periodic maintenance jobs on Mac OS X. I spent some time last night > figuring out how it's being done now. Here's what's happening. > > The way most Unix systems have done the periodic maintenance from > time immemorial is to schedule them as cron jobs. The cron daemon > on a Unix system is a program that runs quietly in the background-- > that's why it's called a daemon--keeping track of a list of > commands and times at which to run those commands. Each user can > have a table of scheduled jobs, called a crontab. The mother of all > crontabs is the system crontab, that's owned by the operating > system itself. The system crontab listed the times to run the > scripts called daily, weekly and monthly, to do periodic maintenance. > > The scripts are still there in the latest versions of Mac OS X. You > just have to look in the /etc directory. The scripts are still > there, but they are not used. > > To tell you what's being done now, I must go off on a tangent. > > Unix systems have had a very confusing way of starting things up > when they are booted. Some things are launched by one set of > scripts and another set of things are launched by another method > entirely. (Linux users should think of rc.d and xinetd.) Apple > wanted to clean this up, so they invented a new traffic cop that's > the very first program launched by the kernel and called it > launchd. (The "d" on the end is a clue that launchd is also a > daemon.) All the startup stuff is handled in one place by launchd. > Most of the functionality of crond was rolled into launchd, so > Apple has turned off cron in Tiger. > > The new launchd periodically calls a program called periodic to > handle the rest of the stuff crond used to do. The periodic program > has its own cleanup scripts in the directory /etc/periodic/daily, / > etc/periodic/monthly and /etc/periodic/weekly. (The /etc directory > is invisible in the Finder because Apple is trying to hide the > geeky Unix stuff from the proletariat.) > > As of version 1.3, MacJanitor calls the periodic program instead of > the old crond scripts, so it should be safe to use it. (I have not > tried it.) > | The next meeting of the Louisville Computer Society will | be January 24 at Pitt Academy, 6010 Preston Highway. | The LCS Web page is <http://www.kymac.org>. | List posting address: <mailto:macgroup at erdos.math.louisville.edu> | List Web page: <http://erdos.math.louisville.edu/macgroup>
