I updated both iOS 8 and Xcode 6 beta. When I connect my phone, it shows up as \"ineligible device\" where you select which platform you want to run on.
XCode proposes restarting the device and that doesn't work. Instead restarting XCode itself did the trick for me.
For me changing the Command Line Tools to Xcode 6 (instead of Xcode 5.1.1) under "Preferences" -- "Locations" -- "Command Line Tools" did the trick..
I've had the same problem. I closed Xcode made sure my phone was connected then reloaded Xcode and that worked for me.
I got stuck on this for forever. Make sure that you didn't choose "Don't Trust" with the computer. If you did, then you will need to make the prompt come up again, and choose "Trust". If your phone is jailbroken, make sure you don't have any tweak (NoAnnoyance for me) that auto chooses "Don't Trust".
After installing new version Xcode, propose install additional components for debugging. If these components not installed, propose Xcode again for installation. Simplest way to check for existence of required components:
This is worked for me!