iOS Devices do not show up on Xcode 6.1.1 - until after rebooting the Mac

I've been having this issue for over a month now. It's not just Xcode but also iTunes, Image Capture, and some other apps that should easily see my devices. I also often get the "trust this computer?" query, but not every time that the Mac starts rejecting my devices.

Instead of restarting the Mac, the other option is to quit Xcode, issue the following command in Terminal:

sudo launchctl stop com.apple.usbmuxd

and then restart Xcode

I don't know why this bug happens, but after searching a lot about it I got a simple but effective solution.

When the problem starts, I tried to restart my machine, re-install Xcode and Command Line tools without results, and after googling about it, I saw that you can fix it removing lockdown folder using the command below and restarting.

sudo rm -rf /var/db/lockdownsudo mkdir /var/db/lockdownsudo chmod go+w /var/db/lockdown

It works for some users so I will leave it here, but in my case it not helped.

As @mahboudz said, you can trigger the command below from terminal with Xcode closed, without restarting the machine.

sudo launchctl stop com.apple.usbmuxd

This time, my problem was gone, until I turn my Mac next day. The problem came back again. I can resolve it again temporary using the command above, but it will happen again and again on every launch.

Knowing the problem is related with com.apple.usbmuxd, I saw on some threads that this process is not only related with Xcode, but USB <-> iPhone device communication.

I fix my problem definitely simply downloading and installing iTunes again after stopping com.apple.usbmuxd process.

In Xcode 6.3 with my iPad, I've found that rebooting the iPad works without having to close Xcode.