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Schedule Mac OSX Update(s) for Offpeak Download using launchd

In order to schedule you Mac OSX software update to run in Offpeak time you can use the launchd system scheduler in order to to accomplish this. On most Unix systems (including cousins and derivates like Mac OSX) you would use cron. While cron is still available on Mac OSX, Apple have provided an Apple centric way of doing the same the work in the form of launchd.

Launchd has a command line control interface that goes by the name of launchctl, which will be using in conjuction with our xml editing skills to achieve this goal.

The software update tool normally accessible via the Apple Menu (Apple->Software Update to be exact) has a command line parallel "softwareupdate". We can use this command line version to run the update in the background at suitably early hour of the morning.

First of all lets construct a launchd configuration file to setup this job for us. In the common Mac OSX fashion this is achieved via the use of a property list file. Essentially an XML file with the information we want in it. A suitable .plist file for this work is listed below. Save this text into a file name like com.krugerheavyindustries.SoftwareUpdate.plist






    Label
    com.krugerheavyindustries.SoftwareUpdate
    ProgramArguments
    
        /usr/sbin/softwareupdate
        --download
        --all
    

    StartCalendarInterval
    
        Hour
        2
        Minute
        00
    

    StandardErrorPath
    /var/log/software-update.log
    StandardOutPath
    /var/log/software-update.log




This particular property list configuration file schedules the software update to run at 2 am every morning.

Now because this task is a system related task we need it to be run by the superuser in order to have sufficient privileges for this to happen. As this is the case I'd be storing this configuration file in /Library/LaunchDaemon

Next we load the configuration file in order to schedule it. We can accomplish this with superuser privileges by the doing the following:

sudo launchctrl load /Library/LaunchDaemon/com.krugerheavyindustries.SoftwareUpdate.plist

We can view the task is loaded and ready to roll by issuing:

sudo launchctl list | grep SoftwareUpdate

You should see the task there, if not, you might have a problem.

The task will run every period you specified until you unload it (or reboot - we did not specify it should load itself).

You can unload the task using the command:

sudo launchctl unload /Library/LaunchDaemon/com.krugerheavyindustries.SoftwareUpdate.plist

On a typically configured Mac, it will be setup to go to sleep if left on for a period of time. Obviously this will affect the running of your scheduled task. In order to make sure you schedule task will run I would schedule your machine to wakeup 5 minutes before the scheduled task is due to run. In this case at 1:55 AM. This just gives subsystems like WiFi time to reconnect to the wireless router.

Sleep scheduling for wake up is done via Apple->System Preferences->Energy Saver->Schedule->Start or Wakeup

When you come back to your system in the morning you should find your software updates ready to install. Replacing the keyword "--download" with "--install" in the property list file above you can get your updates to install (not just download) overnight also.



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