Trouble upgrading OS X, because HD doesn't use GUID Partition Table Scheme

Question

I have a MacBook with Mac OS X 10.5 which I'm trying to upgrade to 10.6. When I run the upgrade 'install' I quickly get to a page where I am supposed to 'Select the disk where you want to install Mac OS X'. There is only one hard drive, so it is auto selected - below that I see a warning message and the only button available is the 'Go Back' button.

The warning message says:

"Macintosh HD" can't be used because it doesn't use the GUID Partition Table scheme.

Use Disk Utility to change the partition scheme. Select the disk, choose the Partition tab, select the Volume Scheme and then click Options.

I followed the above instructions, and arrived at the last step where I'm supposed to click the 'Options' button. The problem is that I can't click that button, it is disabled - so what am I supposed to do?

Answer 1

If as you've said in your comments to another answer you are "OK" with completely reformating your drive, then you can do so by booting from the install disc and then running Disk Utility from the install media to convert the drive to GPT and reformat it. Then proceed with your install of OS X.

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well I just tried rebooting with the osx 10.6 snow leopard upgrade install cd and rEFIt doesn't notice the cd ... I'm unsure how to boot to the upgrade cd if that is what I have to do.

It's been a long time since I used rEFIt so I can't help there. It should detect the SL install DVD and I don't know why it doesn't appear to for you.

There are a number of key combinations that you can try which may help.
Here are some links:
Startup key combinations for Intel-based Macs
Mac OS X keyboard shortcuts
MacRumors Guides "Keyboard shortcuts"

Off the top of my head I would suggest trying:

• Pressing/holding "C" (at the boot bong/startup sound) to force booting from the CD(DVD) drive.

• Pressing/holding the "Option" (Alt) key when booting. This should display a list of all bootable devices and one of them should be the DVD drive. (Of course, IIRC so should rEFIt ...)

• If you can boot OS X from your hard drive and neither of the above worked for you, you can try selecting your optical drive as the "Startup Disk" in "System Preferences" and see if that allows you to boot from it.

• By the way, if you need to eject the media from optical drive and the "Eject" key won't work for you, holding the mouse button down while booting should do that.

In order to format and repartition your drive you have to boot OS X from device other than that drive. Usually the easiest way to do this is to boot from the install media. But another last resort possibility is to install OS X on an external hard drive and then boot from it. (Not something I'd recommend, just saying it's possible.)

if I reformat the disk, then I need to do so with the install osx 10.5 cd right?

Nope. You can do the reformat and the install by booting your Snow Leopard install disc. The one disc does it all, upgrade from an older version of OS X or a clean install.

If you can boot from your SL install disc, then after the startup completes and you've gotten past the language screen, the Install Mac OS X screen should display. Click the ‘Utilities’ menu button and select "Disk Utility". You should then be able to repartition your drive as a GPT drive and then install to it.

Answer 2

You do not have to format the drive. I have found another solution to the issue, but it takes time:

1. Get a hard drive of the same size or larger

2. Create the same partition scheme, format, and choose options GUID partition. (I also named the drive the same)

3. Use Carbon Copy Cloner (free) to clone your drive to the newer drive.

4. Install the new drive into your system and boot.

5. Restart the upgrade app.

6. (optional) If the new drive is a temporary drive you can repartition your old drive with GUID and then Carbon Copy Cloner the data back.

I have just done this and it worked for me - my data is about 120GB though so it took about three hours to copy each time.

Answer 3

The message to the right in the Disk Utility window is telling you that because the partition you selected ("Macintosh HD") is the startup volume, it cannot be erased. This is probably important for a couple of reasons. As far as the computer is concerned, it can't erase the hard drive that it's currently running off of. As far as you're concerned, this drive probably contains all of your data, and you shouldn't erase it without a full backup!

Tiger (I believe? or maybe it was Leopard) introduced native support for non-destructive partitioning, but this only works for resizing existing partitions and creating new partitions in the free space on a drive. I don't believe you can change the partitioning scheme (from MBR in this case, to GUID) without reformatting the drive. Once you've backed up your data and are ready to reformat, you can reboot from the OS X DVD and run Disk Utility from there.

All of that being said, I'm not really sure why your drive is formatted as MBR (Master Boot Record). That scheme is supported for compatibility with MS-DOS. I'm unclear if when you say that you only have one hard drive if that implies that you intend to have it partitioned for multiple operating systems, but even if you do, Boot Camp fully supports NTFS-formatted partitions under a GUID partition table. There should not be any drawback to changing to this scheme, other than the fact that GUID-based disks cannot boot a PowerPC-based Mac.

Answer 4

I had a similar issue when upgrading to High Sierra. I'd purchased a SSD and used Clonezilla and TimeMachine to replicate it. Apparently I'd configured it with MBR & it wouldn't up install High Sierra without GUID partitioning. Here's how I got around it in just a few steps.

1. Created a new time machine backup.
2. Purchased a USB to SATA adapter, installed my old drive in it.
3. Rebooted, held down [option] key to allow booting from USB
4. Used the disk utility to erase my SSD drive and configure it with GUID partition & APFS. Note - kept the same "volume name" for the drive.
5. Shut down, connected the TimeMachine drive, connected laptop via ethernet, rebooted with [command][r] which then did an internet boot.
6. Used time machine option to rebuild my ssd
7. Reboot and run the High Sierra Installer