问题
I'm getting the error "Could not allocate a resource" when I try to run on any of my devices. I've seen this as a possible fix:
sudo rm -rf /var/db/lockdown/
I've tried that and restarted my machine a handful of times, but no luck. I also tried changing USB ports. I've reinstalled Xcode as well after uninstalling with AppCleaner.
In addition to the error, whenever I connect a device it asks me "Trust This Computer?"
This is occurring on an iPhone 5 and iPhone 6+ with lightning, as well as an iPad 3 with the old style connector.
[Updates] I've now also reinstalled iTunes to no effect. Also reset PRAM and SMC.
回答1:
After you delete that folder, you need to recreate again and make proper permissions, because iTunes need rw rights to that folder:
sudo mkdir /var/db/lockdown
sudo chmod go+w /var/db/lockdown
without having iTunes open. Then everything should be fine. Also keep in mind the same operation may be required for /private/var/db/lockdown [a mirror]
If you moved and old Mac to a new one, make sure /var/db/lockdown/SystemConfiguration.plist contains your mac actual UUID . Generally it is not recommended to delete a system folder, anyway, without really knowing what you do. ;) Actually I replicated your problem moving /var/db/lockdown to another location, starting iTunes, getting error. Then recreate etc.
来源：https://stackoverflow.com/questions/28254479/xcode-error-when-running-on-device-could-not-allocate-a-resource