Sysadmin > MacOSX > OSXUseMacOSXServerSoftwareUpdateService

How to use a Mac OS X Server as a cache for Software Updates

Unmanaged clients

Use these steps to point client Macs that aren't managed with a configuration profile or Managed Client to your Software Update server: On the unmanaged client, open Terminal. Use the following command. Substitute your Software Update Server's fully qualified host name for
sudo defaults write /Library/Preferences/ CatalogURL
You can verify your change using this command:
defaults read /Library/Preferences/ CatalogURL
To point an unmanaged client computer back to the Apple Software Update server, use this command:
sudo defaults delete /Library/Preferences/ CatalogURL