My MacBook Pro is off to AppleCare tomorrow, but after I backed everything up to Time Machine, I made sure to make a bootable USB so I can have a fresh install without having to wait for Yosemite to download from the App Store.
In previous years I’ve used DiskMaker X (formerly known as Lion DiskMaker), which has been fairly solid and a great option for those wary of the odd Terminal command. I like the simplicity of using the command line where possible though.
- Once you’ve downloaded your copy of Yosemite from the App Store, it will prompt you to install it. Cancel this for now, even if you haven’t installed Yosemite yet, you can always come back to this part.
- Get a USB stick at least 8GB in size that you don’t mind being wiped.
- Open up Disk Utility(( in Applications > Utilities
)) and select your USB stick in the source window, then the ‘Partition’ tab on the right. - Change the Partition Layout to 1 Partition in the drop-down menu.
- Rename the partition to something other than the default ‘Partition 1’. It’ll be overwritten anyway, but go with something without spaces in it. I chose ‘yosemite’.
- Make sure that the partition format is ‘Mac OS Extended (Journaled).
- In the ‘Options’ underneath the Partition Layout window, make sure that GUID Partition Table is set so that the USB will be bootable.
- Click on ‘Apply’ to wipe the USB stick.
Once that’s done, open up Terminal((in Applications > Utilities 
)) and run the following command. You’ll need to know your admin password, by the way:
sudo /Applications/Install\ OS\ X\ Yosemite.app/Contents/Resources/createinstallmedia --volume /Volumes/yosemite --applicationpath /Applications/Install\ OS\ X\ Yosemite.app --nointeraction
Note: that I’ve put the name of my USB stick in bold so that you know you’ll need to change this to whatever you named your USB stick.
Sit back and wait while the data copies from the installer package to your USB stick. When it’s finished (and it may take some time), it will tell you it’s done.
Congratulations! You should now have a USB stick newly titled ‘Install OS X Yosemite’. If you want to see if it is indeed bootable without restarting your Mac, go to System Preferences > Startup Disk. You should see your new USB installer in the list of volumes available to boot from.