Macintosh: How To Bypass Internal Hard Disk At Startup

How can I bypass the internal hard disk at startup? I know the Macintosh will boot from a floppy disk if I insert one. But what if I want to boot from an external hard disk or CD-ROM?
To start your computer from an alternate startup device outside of the one selected in the Startup Disk control panel, you may hold down a combination of keys during the startup process. This will bypass the selected device in the control panel and go to the next bootable device, be it a hard drive, CD-ROM, or floppy if the computer is so equipped.

Note: Any Macintosh computer (Macintosh IIci or newer) equipped with an Apple compatible CD-ROM drive can boot from the Install Me First CD-ROM or Mac OS disc by holding down the letter C key during startup. For detailed instructions reference Tech Info Library article 18059: "Macintosh: Starting From Floppy or CD-ROM Disc".

When You Need to Bypass the Hard Disk

You might want to bypass the hard disk when booting from a CD-ROM to install new system software or application software. Also when troubleshooting, or using a different system software version you may not want a hard drive volume visible on the desktop.

How To Do It

During the start up process, hold down the following four keys, Command-Shift-Option-Delete, until the Welcome To Macintosh screen appears signifying the computer is booting from the alternate source.

The system starts up from the floppy disk or the next bootable device.

Published Date: Feb 18, 2012