Identify boot drive on a Mac

If you have more than one drive in your Mac you may find you need to identify which one is the startup volume (boot drive, boot partition, etc).

The easiest way I found was to open Disk Utility and see which one was top of the list in there. For further confirmation, click on the volume there and look at the mount point displayed at the bottom - the startup volume is mounted at '/'. Other HDs will be mounted at /Volumes/drivename.

But why would you need to check that?

In my case, it's because both drives are bootable.

I was wondering why my SSD equipped iMac wasn't as fast as I expected. When I had a look it turned out that my old HDD had become the startup volume again - I'm guessing that a system update reset my startup volume for me.

It's simple to change back via System Preferences > Startup Disk and a reboot so not a major problem. 

But why do I have two bootable drives?

Well... whilst it's possible to take an iMac apart and muck about with drives on the inside, it's an utter faff and frankly it seemed easier to get a thunderbolt / sata adapter, plug it in the back and use a cable tie to keep it neat. Thunderbolt is fast enough that an external SSD is just about as fast as an internal one. 

I decided at the time to leave my internal drive as is just in case the change didn't work and never got round to changing it.

New HD in my Macbook

Upgrading the HD in my beloved Macbook was surprisingly simple:

Step 1 - Buy a new drive and prepare it with Disk Utility: 'Erase' the new disk and let it format as the default (Mac OSX Extended Journaled)
Step 2 - Download some cloning software. I used Carbon Copy Cloner (donationware).
Step 3 - Clone that bad boy. CCC lets you do this whilst the drive was active so there's no need to reboot into a live CD.
Step 4 - Give it some time . . . about a minute per MB. It took a little over 3 hours to clone the 200 GB or so I had, so being a little drunk by this point I went to bed and left it going.
Step 5 - Optional: blessed sleep followed by mild hangover.
Step 6 - Test it's ok by rebooting and holding the 'option' key so I can boot from the drive in the caddy.
Step 7 - Swap out the drives.
Step 8 - Compulsory: bask in the glory of just how 'on' your geek was.


After you're done:
If you used the defaults, your drive is probably now called 'untitled' instead of 'Macintosh HD'. If you want to change the name, you can do it via 'Get Info' in the context menu. I called mine Rosebud.

Assumptions:
You have the wit to find alternative instructions if this didn't tell you all you needed to know.
You have some kind of USB or SATA caddy you can use to connect the new drive to.
You can find Disk Utility.
You have the wit to find out how to remove and refit a drive.