Boot from USB drive containing Mac OSX dmg file

al4629740
al4629740 used Ask the Experts™
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So I'm not sure what I'm doing wrong but I'm trying to create a bootable Mac OSX USB drive.  I'm creating it from a Windows 10 machine.  I downloaded TransMac, formatted my thumb drive and then restored an image of 10.8 DMG file to the thumb drive.  Then when I try to use it by booting to the USB drive on the Mac, it does not show up as one of the drives I can boot to.  Has anyone tried this before and what am I doing wrong?
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Jackie Man IT Manager
Top Expert 2010

Commented:
Have you tried another USB port or use another USB thumb drive?

https://forum.amd-osx.com/viewtopic.php?t=3276

Author

Commented:
I tried another thumb drive.
You may have to bless the disk from a Mac system first.

 bless --folder "/Volumes/Mac OS X/System/Library/CoreServices" --bootinfo "/Volumes/Mac OS X/usr/standalone/ppc/bootx.bootinfo"

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man bless
BLESS(8)                  BSD System Manager's Manual                 BLESS(8)

NAME
     bless -- set volume bootability and startup disk options

SYNOPSIS
     bless --help

     bless --folder directory [--file file] [--bootinfo [file]] [--bootefi [file]] [--label name | --labelfile file] [--setBoot]
           [--openfolder directory] [--nextonly] [--shortform] [--legacy] [--legacydrivehint device] [--options string] [--personalize]
           [--quiet | --verbose]

     bless --mount directory [--file file] [--setBoot] [--nextonly] [--shortform] [--legacy] [--legacydrivehint device]
           [--options string] [--personalize] [--quiet | --verbose]

     bless --device device [--label name | --labelfile file] [--startupfile file] [--setBoot] [--nextonly] [--shortform] [--legacy]
           [--legacydrivehint device] [--options string] [--quiet | --verbose]

     bless --netboot --server url [--nextonly] [--options string] [--quiet | --verbose]

     bless --info [directory] [--getBoot] [--plist] [--quiet | --verbose] [--version]

     bless --unbless directory

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Author

Commented:
How do I get to a command prompt to execute?  is that under utilities because I don't see it.
Jackie Man IT Manager
Top Expert 2010

Commented:
You need to have access to a computer running OS X to run the above command.

Author

Commented:
So basically I can’t run the above command because the drive is new
Here's the thing:

Apple licenses OS X to only run on Apple computers.  If you did this from a Mac, all would work just fine.  You're trying to do it from Windows, something they don't officially support, so it's all a hack.  You'll need to get your hands on a Mac and see if it works, once it works, then you can attempt it on your non-supported platform.  Other people have done it, but they likely had access to mac hardware to get started.

A DMG file is also not an ISO.  It might contain an ISO and can be converted into an ISO format, but creating a bootable image from it can really only be done from a Mac, as officially supported by Apple.

Unless, you also match the hardware, there won't be drivers for your hardware, and it's going to run so excruciatingly slowly that it's not worth the time and effort, except as a proof of concept.  I've done those for some people just to prove that it can be done, and it either sat idly for the occasional showing off or it got wiped and replaced with Linux.  You'd save so much time just getting an older Mac.

Author

Commented:
But that’s the thing, I AM using this on a MacBook Pro.  I’m not sure I understand if you mean that I should run the boot disk on a working Mac first but I’m confident the file works fine.  The only thing is if I can just create everything from a Mac first then everything will probably work...
Ok.  Why did you need to create the boot image from a Windows machine?  Did your Mac disk get wiped?  Is your system really old?  Did you create the ISO installer disk correctly?

You can't just extract the Installer DMG onto the USB to boot.  You need to extract the ISO within the installer DMG.  If you're saying this is a bootable disk that you converted to a DMG, then you may need to bless the USB to make it bootable.

If your Mac was bought with a default OS X that was later than Lion (10.7) you can reinstall it from the internet and it will then install the original copy of OS X that came with your computer.  Connect it to the internet, then start the computer with command option r and select Install.  You can format the disk if you like.

You only need the installer disc if your OS was earlier than 10.7.

If you're able to install from the internet and you need to "recover" that DMG "boat" disk, you can run Migration assistant.app and "migrate" the images from that USB.

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