bypass dead imac hard drive and boot from external hard drive?

**daveb123** · July 8th, 2009, 03:51 AM

My imac G5 isight's hard drive is dead. I would like to install OS X on an external hard drive and just use that as the hard drive for this machine. My questions are:

Can I boot from an external hard drive via USB and just run everything off the external hard drive? If so, how should I format the external hard drive so that it can be selected and written to when I boot from the install cd? The external hard drive I would like to use is a 75 gig Acom. I've tried booting from the install cd, and it either won't even find the external hard drive, or, when it does, it says it can't write to that external hard drive.

**ElDiabloConCaca** · July 8th, 2009, 08:23 AM

You probably need to format the external drive first. Launch "Disk Utility" (in the "Utilities" menu after you select a language when booted from your OS X install CD/DVD) and highlight your external hard drive. Click the "Partition" pane, select 1 partition (or whatever suits your fancy), then select "Mac OS Extended (Journaled)" and click "Partition".

Quit Disk Utility, and the disk should now show up as a valid install location.

Be aware that this procedure erases everything on the external hard drive, so ensure that the data that is currently on the external hard drive is backed up somewhere else.

**daveb123** · July 8th, 2009, 08:57 AM

Thank you. I tried that already, and when I reformatted the external hard drive as Mac OS Extended (Journaled), the external hard drive wouldn't show up at all. Any other ideas?

**ElDiabloConCaca** · July 8th, 2009, 08:58 AM

Instead of doing a "reformat," try a "repartition" -- highlight the hard drive, click the "Partition" pane, select your partition scheme and disk format (Mac OS Extended), then click the "Options..." button at the bottom of the window. Ensure that "Apple Partition Map" is selected in that "Options..." window.

**daveb123** · July 8th, 2009, 09:14 AM

Still no dice. A little more background info, this Acom drive I am trying to use was the only DiskWarrior could find when I was salvaging my data from this imac. It wouldn't find the two Western Digital drives or the Vantec NexStar either. So I know it can be found. After using it to transfer all my files from DiskWarrior, I decided to use it as the external boot drive and didn't think it needed to be reformatted because DiskWarrior had found it. I booted the imac using the install disk, and the Acom couldn't be found. I've tried reformatting a couple of different ways (what you've just suggested, along with two partitions, one os extended (journaled) and the second partition ms-dos, just taking shots in the dark. Any other suggestions?

**ElDiabloConCaca** · July 8th, 2009, 09:17 AM

Strange... I know that PowerPC-based Macs cannot boot from USB devices, but apparently, Leopard changed that and now they can.

Is the drive USB or FireWire (or both)? If both, try connecting it via FireWire (or if you have a FireWire drive laying about, try that one).