To set startup to JUST the Macintosh OS in System 6, do the following steps:
1) If A/UX already launches automatically, then cancel the automatic launch
sequence.
2) Quit from the A/UX Startup.
3) Make sure nothing is selected; click in the open desktop area.
4) Pull down the Special menu and select the Set Startup command.
5) Click the OK button.
Conversely, to set startup to A/UX Stand-alone shell automatically, and
hence have A/UX boot automatically, do the following steps:
1) Make sure you are at the Finder level.
2) Click the A/UX Startup icon.
3) Pull down the Special menu and select the Set Startup command.
4) Click on the OK button.