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I am unable to expand my Mac's hard disk. diskutility reports this error:

MediaKit reports partition (map) too small

How can I resolve this?

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4 Answers

This blog post was the only way I found to solve it, and it's not for the faint of heart. ;-)


Basically the problem is that the GUID partition table is confused about the size of the drive. The only way to fix it is to purchase a tool that will correct the problem, or to manually correct the problem yourself by issuing commands to gpt to delete and recreate the partition table. You must create it exactly how it was before, including the partition types (UUIDs).

Also, you must be able to get a root prompt where the drive you're interested in isn't mounted. (for me, this meant popping in the install disk, booting from it, then quickly pressing Command-S to enter single-user-mode.)

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If you start the GParted live cd: http://gparted.sourceforge.net/ On your system it will automatically detect and fix this issue. Best solution I found so far.

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Nice. I guess most recent Macs use HFS+ (Mac OS Extended), which seems to be supported for checking a partition according to its feature overview. –  Arjan Feb 2 at 12:59
Worked like a charm--this is the best answer--needs more up votes. –  scotru Apr 28 at 7:53
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I know it is a late response. Now only I faced this issue and I find out this blog INCREASE DISK AND PARTITION SIZE IN OS X. This solved me my issue. I am posting this because this might help someone else I hope.

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Why not just boot into single user mode? Hold down command+s on boot. Performcheck disk and then mount the drive.

Go to /Library/Caches and /System/Library/Caches and remove everything in those folders.

Then go to /private/var/db and remove BootCache.data, BootCache.playlist and .volinfodatabase. Reboot and use Disk Utility again. Just did this here and it worked moving from a 120GB SSD to a 250GB SSD. Was getting the dreaded medikit error too small or whatever.

You might just have to remove the .volinfodatabase. Try that first. If that doesn't work try the .volinfodatabase again and the BootCache files. If that doesn't work try what I tried.

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