Resizing OSX virtualbox guest partition

README.md

Expand virtual hard drive

VBoxManage modifyhd OSX\ Dev.vdi --resize 40960

Resize GPT

Solves "MediaKit reports partition (map) too small" error from Disk Utility

• Mount virtual image via nbd sudo qemu-nbd -c /dev/nbd0 OSX\ Dev.vdi
• Use sudo gdisk /dev/ndb0 to destroy and recreate a partition table.
• Unmount virtual image sudo qemu-nbd -d /dev/nbd0

Fix volume information headers

Solves "Couldn't modify partition map because file system verification failed" error from Disk Utility

• Boot OSX in single user mode (pass -s to bootloader)
• fsck -fy

Actually resize partition

• Boot OSX normally
• Open Disk Utility
• Select (now larger) drive on left
• Partition tab
• Drag up and then down
• Click Apply

Done!

Hi!
I've followed your instructions as closely as I could, but when I boot OSX, the drive is still the previous (smaller) size.
One point is not very clear to me: how to destroy and recreate the partition table. I ran the command (gdisk....) and then quit, but the disk size does not change in OSX.
If I try to make further manipulations in gdisk (deleting and re-adding the partitions), I can no longer boot OSX to single user mode: it keeps saying "still waiting for root device". I forgot to mention It's my root partition that I want to make larger.
Can you help me?
Samuel

@ytsamy try this approach:
http://blog.kyodium.net/2010/11/increase-disk-and-partition-size-in.html
In recent OS X there are multiple entries for EFI, but read the latest comment to learn how to play with them.