Another use for gdisk, for moving a Lion installation with Recovery HD to a new 
larger disk.

With Snow Leopard you could simply boot from a 2nd disk and:
dd /dev/disk0 /dev/disk1 bs=1M
diskutil resizevolume /dev/disk1 limits

and you figure out how much bigger you can make it, and then fill in the blank 
in G like:
diskutil resizevolume /dev/disk1 749G

Done.

But in Lion this won't work by default because you will have a Recovery HD 
partition in the way of your main system/data partition and the unallocated 
space of the new disk. So resize won't work. In retrospect it seems to me Apple 
should have put the Recovery HD as slice 2, and Lion main in slice 3. But 
whatever...

Using gdisk you can make a new 620M partition with ab00 partition type at the 
end of the new disk as disk0s4 then dd disk0s3 (recovery hd) to disk0s4. That's 
it, you have two Recovery HDs now. Next gdisk to remove the old Recovery HD 
leaving a pile of unallocated space in between disk0s2 and disk0s4. Diskutil's 
resize will now work and let you add in all that unallocated space by growing 
disk0s2.

Way faster than cloning to a larger disk.

Now if you're using FileVault 2 with Lion...that's a bit more tricky because 
unlike LVM2, CoreStorage does not appear to have a (documented) way to move 
physical extents from one physical volume to another, whether you're using 
encryption or not.


Chris
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