Mac Boot Options

Mac Boot Options 

1. Key Combination -- Effect
2. mouse down -- Eject removable media ( I think Boot ROMs prior to 2.4f1 excluded the CD drive )
3. opt -- Bring up OF system picker on New World machines
4. cmd-opt -- Hold down until 2nd chime, will boot into Mac OS 9 ?
5. cmd-x (or just x?) -- Will boot into Mac OS X if 9 and X are on the same partition and that's the partition you're booting from.
6. cmd-opt-shift-delete -- Bypass startup drive and boot from external (or CD). This actually forces the system to NOT load the driver for the default volume, which has the side effect mentioned above. For SCSI devices it searches from highest ID to lowest for a partition with a bootable system. Not sure about IDE drives.
7. cmd-opt-shift-delete-# -- Boot from a specific SCSI ID # (# = SCSI ID number)
8. cmd-opt-p-r -- Zap PRAM. Hold down until second chime.
9. cmd-opt-n-v -- Clear NV RAM. Similar to reset-all in Open Firmware.
10. cmd-opt-o-f -- Boot into open firmware
11. cmd-opt-t-v -- Force Quadra AV machines to use TV as a monitor
12. cmd-opt-x-o -- Boot from ROM (Mac Classic only)
13. cmd-opt-a-v -- Force an AV monitor to be recognized as one
14. c -- Boot from CD. If set to boot to X and no CD is present, may boot to 9.
15. d -- Force the internal hard disk to be the startup device
16. n -- Hold down until Mac logo, will attempt to boot from network server (using BOOTP or TFTP)
17. r -- Force PowerBooks to reset the screen
18. t -- Put FireWire machine into FireWire Target Disk mode
19. z -- Attempt to boot using the devalias zip from first bootable partition found
20. shift -- (Classic only) Disable Extensions
21. shift -- (OS X, 10.1.3 and later) Disables login items. Also disables non-essential kernel extensions (safe boot mode)
22. cmd -- (Classic only) Boot with Virtual Memory off
23. space -- (Classic only) Trigger extension manager at boot-up
24. cmd-v -- (OS X only) show console messages during boot
25. cmd-s -- (OS X only) boot into single user mode