Open Firmware and bootup shortcuts

Question

Open Firmware and bootup shortcuts

Is there any way under open firmware to view the bootup shortcuts, and/or modify them, such as holding down C to boot up from the CD, etc?

PowerMac G4 Dual 800; iBook G3 600 16 VRAM, Mac OS X (10.4.8)

Posted on Jan 8, 2007 10:32 PM

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Answer 1

Jan 15, 2007 2:32 PM in response to smtlaissezfaire

Hi,

The key commands happen before open firmware gets called (that's how you get to open firmware - hold down option + command + O + F )

I like the links below for keys

http://docs.info.apple.com/article.html?artnum=303124 (intel macs)
http://docs.info.apple.com/article.html?artnum=58029 (older macs)

Do be careful typing in open firmware - it's easy to toast the firmware or erase a drive if you are not careful - it's not a forgiving user interface 😉

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Answer 2

Jan 17, 2007 8:19 AM in response to Michael Bradshaw

Or you could set the variable auto-boot? to false in open firmware. This no longer allows of those key sequences to work - so it seems that those variables in open firmware must first be referenced before the key sequences work.

There is also a way to set a password in open firmware which should secure it completely, and renders it a large brick if the password is forgotten. See this O'Reilly article:

http://www.linuxdevcenter.com/pub/a/mac/2003/02/18/secure_tibook.html

But, it may be possible that Open firmware itself has no access to these key sequences, but only allows them to be used. That is, the key sequences may be programmed into the hardware itself.

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Answer 3

Jan 17, 2007 4:48 PM in response to smtlaissezfaire

That is, the key sequences may be programmed into the hardware itself.

No, they are caught in the initial stages of Open Firmware, which gets control immediately after P.O.S.T.

It recognises c, d, n, t, x, z, Option, Shift, Command-Option-o-f, Command-Option-p-r, Command-Option-Shift-Delete, Command-s, and Command-v. Some of these (like the last two for example) are passed on when it has determined the boot device.

The Open Firmware password is easily got around if you have physical access to the machine (but then so is almost all security).

I wouldn't play around with Open Firmware variables unless you know exactly what you are doing.

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Answer 4

Jan 21, 2007 1:18 PM in response to Michael Conniff

What do all of those key sequences represent?
C-Cdrom
D-disk
n-network
t-target disk mode
x-?
z-?
Option- menu for boot device
Shift-?
C Opt+OF = open firmware
C Opt+Shiftdelete = ?
Command-S = ?
Command-V = ?

How does one get around the security password in Open Firmware?

Also, why do you make that last comment? Is there really some way to render the machine unusable or destroy it permanently through open firmware?

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Answer 5

Jan 21, 2007 2:36 PM in response to smtlaissezfaire

What do all of those key sequences represent?

You got a lot of them, here's the rest:
x = boot OS X rather than OS 9 if both are present
z = zip drive
Shift = Safe Boot
Command-S = Single User
Command-V = Verbose

How does one get around the security password in Open Firmware?

I'm not going to post that here. Suffice to say it can be found if you know where to look.

Is there really some way to render the machine unusable or destroy it permanently through open firmware?

Basically you can cause permanent damage that will require hardware repair.

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Answer 6

Jan 21, 2007 4:38 PM in response to Michael Conniff

Wow. Really surprising. I'm no "elite" hacker (I have never had any idea how to spell it numerically, which I suppose excludes me from the beginning).

I only figured out after asking the question that it might sound too sinister to actually deserve a response.

I guess I've always taken it as a maxim (coming from the PC world, which is filled with viruses, spyware, etc), that software could never damage hardware. I imagined that a BIOS could be corrupted, but nothing that would ever cause actual hardware damage! But maybe I'm just not from an old enough, Woz-era school of computing.

I'll be more careful in open firmware. Thanks for the advise and sparking my interest on the subject.

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