React Native Build Commands Failed: PhaseScriptExecution ... (domain=NSPOSIXErrorDomain, code=2)

Try running react-native upgrade

See Github thread: https://github.com/facebook/react-native/issues/7308#issuecomment-219597774

For me port 8081 was in use :

lsof -n -i4TCP:8081

1.Go to File -> Project settings 2.Click the Advanced button 3.Select "Custom" and select "Relative to Workspace" in the pull down 4.Change "Build/Products" to "build/Build/Products" 5.click done, done