OS X 10.10 DP1 USB media creation

Use and 8GB+ USB stick and format it with GUID partition mapping and a partition named Untitled, then run the following in terminal:

sudo hdiutil attach ~/Downloads/Install\ OS\ X\ 10.10\ Developer\ Preview.app/Contents/SharedSupport/InstallESD.dmg
sudo asr restore -source /Volumes/OS\ X\ Install\ ESD/BaseSystem.dmg  -target /Volumes/Untitled -erase -format HFS+
sudo rm /Volumes/OS\ X\ Base\ System/System/Installation/Packages
sudo cp -a /Volumes/OS\ X\ Install\ ESD/Packages /Volumes/OS\ X\ Base\ System/System/Installation/Packages
sudo cp -a /Volumes/OS\ X\ Install\ ESD/BaseSystem.dmg /Volumes/OS\ X\ Install\ ESD/BaseSystem.chunklist /Volumes/OS\ X\ Base\ System

1. In applications folder, right click on Install OS X 10.10 Developer Preview, choose «Show Package Contents».
   
2. Open Contents / Shared Support
   
3. You’ll see a Packages folder. Open terminal, enter: open "/Volumes/OS X Install ESD/BaseSystem.dmg
   
4. Using Disk Utility, restore OS X Base System to your USB Stick. (Took a couple of times for me)
   
5. On the USB Stick, in System/Installation delete the link named Packages
   
6. Copy Packages from OS X Install ESD to the System/Installation folder on the USB Stick
   
7. Unhide files from the OS X Install ESD dmg to copy BaseSystem.dmg and Basesystem.chunklist (they are both hidden) and copy them onto the USB stick (not in a folder, top level)
   
8. Unmount USB stick. You now have a full bootable USB stick with the OS.
   
   

Good luck!

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