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TICKET ARCHIVE -> Can't boot from ISO

RobinS - Jan 28, 2008 - 7:52 pm

I want to create some diagnostic discs and presume I should be burning them in ISO format. Also I want to make a copy of my valuable install DVD. I tried with ISO since I thought that was a direct copy but OS X won't boot from it. I'm using an external firewire DVD burner. Other stuff burnt on it is fine. Can you boot from an ISO in OS X?

earthsaver - Jan 29, 2008 - 12:33 am

ISO is a type of disk image format. You can't boot from a disk image, though it sounds like you're actually burning a copy, which is why ISO seems out of context. However, instead I think you're looking to make a CD/DVD Master image.

I normally use Toast to duplicate discs bit for bit.

- Ben

RobinS - Jan 29, 2008 - 12:22 pm

I've got a program that has diagnostics on it that I need to boot from (outside of OS X). Its an ISO burnt with Toast 8.

Is this possible?

Or should I burn this as something else (with a different extension?

Should I have used a disk image in Disk Utility?

Should a windows machine be able to boot from an ISO?

I've never understood the point of disk images. Are they just a compilation of files grouped together? If so, I wonder why they didn't call it a group file? Strange how people so often don't use plain English when it could be used. Look forward to hearing from you!

earthsaver - Jan 29, 2008 - 1:52 pm

The term image has been used for years to describe normally all the files associated with a computer such that the image could be restored onto the computer to make it useable by a new user. In the case of a disk image, Apple has offered the ability to package a physical disk in a digital way. ISO is about the only form of this that has ever been possible on Windows. Apple has used disk images for years to distribute software updates.

Anyway, I need to make sure that you burned the contents of the ISO and not the ISO file itself. Regardless of the type of disk image file, its content is what's important in terms of being able to start up a computer from a burned disc containing that content.

Strange how people continue to use the word "boot" to refer to computer startup.

RobinS - Jan 29, 2008 - 11:24 pm

So to boot something on a PC you need an ISO?

But an ISO won't boot on a Mac?

So it should be a .dmg?

To experiment I tried opening the ISO on a Mac, then it displayed its contents. (A few files and folders I think.) Then I copied the entire contents to a blank DVD. Didn't boot. In Toast, I just copied the data to boot on a PC or Mac. Should I have done something else so it booted up? It just won't see it. Yet other DVD's boot up fine. I should mention that I burnt it on a Mac but for the time being I'm trying to boot up on a PC. I've got a Memtest CD that boots up fine on the PC and is great for testing memory. Are DVD's harder for some computers to see? And since Macs use Intel boards/cpu's now, I wonder if I could use the same diagnostic DVD/CD's for measuring both Macs and PC's?

earthsaver - Jan 30, 2008 - 9:48 am

I don't think it matters what type of disk image you use. That's just a means of transporting the data until you burn it. I don't know about Toast, which you might need to use to burn a DVD for a PC, but in Disk Utility, when you tell it to burn a disc from a disk image, it fetches the contents of the image. The other thing you'd have to be careful about, manually copying data to be burned for Mac startup, is that you've captured all the files that are normally invisible in the Finder.

Anyway, I don't know what PCs look for in a startup disk. Also, I don't think you can necessarily start up both Mac and PCs with a single disc if the Intel-based Mac has EFI firmware and the PC has BIOS. I've also never booted a PC from a DVD, so I don't know if PC's expectation is any different. Maybe another tech knows.

But first, where did the data for this DVD come from? The best way to copy a disc to burn to another disc is to use Toast's Copy function.

RobinS - Jan 30, 2008 - 10:47 am

This is starting to make more sense. Thanks for your input. I'd like to run this by another tech though. Especially regarding if its possible having one diagnostic disc bootable from both Macs and PC's. That would be very convenient as they use basically the same parts. Even more convenient would be to also have those files on a USB thumb drive. But if its not bootable, there's not much point.

TechSupport - Feb 2, 2008 - 10:50 am

We apologize for not being able to resolve the issue you asked of us. It is the absolute worst case scenario for us to do this. In our review of why this happens, it generally is related to either the particular issue being addressed or frequently, incomplete or incorrect information provided. We hope by moving your request to the public forums that you will be able to get a solution without leaving you empty handed.

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