Press Apply to restructure the USB volume with the new parameters. Under Partition Information, change Format to Mac OS Extended (Journaled) and give the drive the name “Untitled” (this allows your drive to work with the Terminal commands below you can rename the drive when the process is complete).

Then click Options, choose GUID Partition Table, and click OK to save the change. In the drop-down menu under Partition Layout, choose 1 to create a single new partition. This won’t work for Yosemite, so we need to change it.

In our case, our drive is brand new and formatted as a FAT volume with a Master Boot Record partition scheme. The partition scheme and volume properties of your flash drive will vary depending on manufacturer and previous configuration. With the USB drive selected, choose the Partition tab on the right side of the window. Note that you want to select the drive and not the volume. We’re using a SanDisk Cruzer flash drive, so in our case we choose 8 GB SanDisk Cruzer Media and not the default “No Name” volume. In Disk Utility, select the USB flash drive from the list on the left. Plug the drive into a Mac running OS X 10.7 Lion or higher and launch Disk Utility from the /Applications/Utilities folder. While it’s possible to create a separate partition for the Yosemite USB installer, it’s safest and easiest to use an empty drive or one that you don’t mind erasing. Grab a USB flash drive that’s at least 8GB in size. It will also launch the Yosemite installer app when the download completes. This will put a file called Install OS X 10.10 Developer Preview.app in your /Applications folder. Step 1: Obtain the Yosemite Developer Preview Installerĭownload the OS X Yosemite Developer Preview installer from the Mac App Store.

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