In the GF Admin Guide there is a section titled:
Tools for Extending and Updating GlassFish Server
This section needs:
1) An introduction to Update Center and then a breakdown of the tools which are available. That includes updatetool, software update/notifier and the pkg command.
2) A section that discusses the various GF repositories which are available and how to access packages on those repositories. This may include discussing how to change the preferred repository for a GF installation.
3) How to enable/disable the notifier post installation.