1. 먼저 라이온용 xcode4.3 을 다운 (xcode 4.2 가 설치되어 있다는 전제하에)
2. 다운받은 dmg 마운트
3. 터미널에서 아래 명령어 실행
sudo
cp
-R
/Volumes/Xcode/Xcode
.app
/Contents/Developer/Platforms/iPhoneOS
.platform
/Developer/SDKs/iPhoneOS5
.1.sdk
/Developer/Platforms/iPhoneOS
.platform
/Developer/SDKs/
sudo
cp
-R
/Volumes/Xcode/Xcode
.app
/Contents/Developer/Platforms/iPhoneSimulator
.platform
/Developer/SDKs/iPhoneSimulator5
.1.sdk
/Developer/Platforms/iPhoneSimulator
.platform
/Developer/SDKs/
sudo
cp
-R
/Volumes/Xcode/Xcode
.app
/Contents/Developer/Platforms/iPhoneOS
.platform
/DeviceSupport/5
.1\ \(9B176\)
/Developer/Platforms/iPhoneOS
.platform
/DeviceSupport/
sudo
cp
/Developer/Platforms/iPhoneOS
.platform
/version
.plist
/Developer/Platforms/iPhoneOS
.platform
/version
.plist.bak
sudo
cp
/Volumes/Xcode/Xcode
.app
/Contents/Developer/Platforms/iPhoneOS
.platform
/version
.plist
/Developer/Platforms/iPhoneOS
.platform
/version
.plist
출처 : http://2rang.tistory.com/74