Changing partition size on external SSD?

I posted this over at Macrumors, but I didn't get a response.

I'm looking into getting a Seagate Thunderbolt Adapter and an extra 256GB SSD for installing Boot Camp on the rMBP. I found these instructions on another thread:

Basically, you just clone the BC partition from the internal SSD to the external - simple enough. However if I wind up taking this approach I will be getting the base rMBP model with the 256GB internal SSD. As such, my temporary internal Boot Camp partition will only be about 128GB. My question is, once I clone the 128GB internal partition to the 256GB external SSD, will I be able to change the size of that partition to 256GB so I can take advantage of the entire SSD? Does that phrasing make sense?

 

if i understand any of this, what about placing a "cloned BC partition" on the external SSD would no longer allow you to access the remaining ~128GBs?

 

I've never used BootCamp before, I just assumed that the size of the internal partition would stay the same when I transferred it to the external. Is that not correct?

 

That really depend son what you use to migrate. I personally have migrated partitions and the software did the resizing automatically if the option was selected. I successfully moved a 64GB M4 to a 128GB and a 240GB to a 256GB SSD like this. I also migrated from a 64GB to a 240GB, but that time around i partitiones the 240Gb and used clonezilla. When i migrated to a 160GB Intel 320, Acronis did the resizing too.

 

I'm not particularly familiar with Mac filesystems, so do ask about this method at Macrumours or somewhere like that before trying it. But, my first thought is, try GParted as part of the System Rescue CD. The System Rescue CD is a live boot Linux CD with a bunch of tools for helping recover busted systems (not necessarily Linux ones, either). One of its tools is GParted, a partition manager which, amongst other things, can extend (and shrink) partitions. It supports a ton of partition formats, so it wouldn't surprise me if it would work in this case, too - but it would be best to check first.

If it does work, the good news is that it's also free, so you've just saved yourself two Hamiltons.