The only external device I have to transfer my ISO image to from my MAC's hard drive is an empty NTFS-formatted external drive (which, I just realized, I could potentially format to FAT32).

But is there any way to install the upgraded operating system to the Mac using mounting software - without transferring the ISO install image to an external device?


As far as the mounting goes: I strongly doubt it.

You could use Disk Utility to clone any installation media you have to the USB drive, making the USB drive bootable and usable as an installation medium itself.
At least that's how I seem to recall it.

Perhaps this forum post helps. Or this article.


In order to run the install, you need to reboot from the install media, and the reboot would kill whatever mounting software you were using. But there may be another way: if you have Leopard on the Mac now, you can use Disk Utility to shrink the current boot volume and create a new additional partition big enough to hold the installer:

  1. Make sure you have a current backup of anything important on the Mac. I haven't seen this process fail in a way that lost data... yet.
  2. Mount the image, and find out how big the volume is (you'll need this later).
  3. Dismount the image, and quit all unnecessary programs (this process is more likely to have trouble if other things are happening at the same time).
  4. Run Disk Utility, and select the Mac's internal disk drive in the sidebar (note: make sure you select the drive, note the volume name listed under it).
  5. Select the Partition tab on the right.
  6. Click the + button under the partition diagram.
  7. Select the new partition in the diagram, and set its size (on the right) just slightly larger than the image volume. Make sure this leaves enough free space on the boot volume for the installation (roughly 5-10GB, depending on how many languages, printer drivers, etc you want to install).
  8. Click the Apply button, and wait a while for the repartitioning process to complete.
  9. When that's done, select the Restore tab on the right.
  10. Drag the new partition from the sidebar to the Destination field.
  11. Drag the image into the Source field (depending on the image format, you may be able to simply drag the image file in from the Finder; if that doesn't work, mount it and drag the volume in from Disk Utility's sidebar).
  12. Make sure the Erase Destination option is checked, click the Restore button, and wait for that to complete.
  13. Now reboot from your shiny new installer partition, and install normally.

Removing the install partition when you're done is fairly similar; select the install partition in the Partition tab, and use the - button to remove it.


Yes! I just did it with an 8GB USB drive. Use Disk Utility to perform a restore of your system image disk to the USB and ensure that "Erase destination" is checked (important). I had a dmg of the Snow Leopard install but the ISO should be very similar. Then restart with the option-alt key held down to bring up the boot disk screen. Start-up from the USB Drive. It surprised me that Mac can boot from USB now but since the MacBook Air they have made provision for this kind of install disk.


You don't even need an external device. Just use the disk utility to 'restore' the iso to a separate volume on the drive you want to install to. For instance, here's how i did it on my old powerbook G4:

create a new volume that's big enough to hold the install image, use disk utility to restore the image to the new volume.

Reboot using the new volume as the startup disk, use disk utility to erase an install to the other volume, and you're good to go.

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