Daily Script
If the rwho system has been configured, clear out the old files in /var/rwho
Clear out files old files and directories in the /tmp and /var/tmp directories
Remove system messages older than 21 days
If system accounting is on, process the accounting files and gather daily statistics
Backup the NetInfo database
Output the disk capacities and storage available
Show which filesystems haven't had 'dump' performed on them in a while (archaic)
Show accumulated network statistics and network uptime (ruptime)
Rotate the system.log file and restart the syslog process
Clear out the webserver log files older than a week
Run the /etc/daily.local script if it exists
Run a /etc/security check script if it exists
Weekly Script
If the /usr/libexec/locate.updatedb database exists, update the 'locate' database
If the /usr/libexec/makewhatis.local file exists, rebuilt the 'whatis' database
Rotate the following log files: ftp.log, lookupd.log, lpr.log, mail.log, netinfo.log
Restart the syslog process
Run the /etc/weekly.local script if it exists
Monthly Script
Run the login accounting process
Rotate the wtmp log files
Restart the syslog daemon
Run the /etc/monthly.local script if it exists
Notes
Several of the tasks that the built-in scripts perform will trigger a domain name (DNS) lookup while it looks it the host name of your Mac. Certain types of connections (such as dial-up PPP connections) will automatically connect to the internet when this happens.
This is NOT MacJanitor doing this -- it's the built-in system maintenence scripts causing it.
To duplicate the same behavior without using MacJanitor, you can execute these built-in scripts using Terminal, like this:
sudo sh /etc/daily
sudo sh /etc/weekly
sudo sh /etc/monthly
In other environments, such as if you have no way to connect to the internet, the portions of the scripts that cause the DNS lookups may hang for a few minutes while the DNS lookup times out. Be patient, and it will eventually continue and complete.