I want to run my app on both simulators ios6 and ios7. I'm trying to install ios 6 simulator but I am getting this error:
Failed to install "iOS 6.1 Simulator"
An unknown error occured. Please try again later.
I restarted XCode but not working stil..
Try to reset iOS 6.1 simulator from menu "iOS Simulator -> Reset Content and Settings...",
then run your app in XCode. This helped me.
Was having the same problem ,
already did a system restart and reset the simulator but didn't work
but
deleting the app manually inside the simulator worked for me,
Run it in iOS 7 simulator (so you can run it), once there, go to "Hardware > Device > select some iOS 6 or earlier device", then apply the "iOS Simulator -> Reset Content and Settings..."
I got exact same problem and solved by using following way,
Launch the iOS Simulator
Go and click "iOS Simulator" Menu
Click "Reset content and settings"
Close simulator and rebuild your app.
Above screen shot is showing the way how you can do this...
I think this works for you...!!!
I had this issue after update to XCode 5. Running an application on the available iOS 7 Simulator and setting the "Enable this mac for developing" check in the popup has solved the problem.
If you use XIB or Storyboard. You have to set document type to "XCode 4.6"
choose storyboard -> inspector (right pane) -> first tab (identity and type)
I had the exact the same issue. I restart my Mac and I'm now download it.
EDIT: I tried everything else. I'm sorry not to be able to answer by given a more useful option.
来源：https://stackoverflow.com/questions/17984150/failed-to-install-ios-6-1-simulator-xcode-5