I tried to install iOS5 beta to Apple TV for using Air Mirroring with iPad
but I couldn’t get an UDID from Apple TV by many ways in internet or just normal way like an other device by iTunes
and~ Here’s a solution!
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You need…
1. USB cable for connecting Apple TV
2. iPhone configuration utility from Apple Web Page
http://support.apple.com/kb/dl851 [for MAC]
http://support.apple.com/kb/dl926 [for Windows]
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Here we go!
1. Plug out all cables from Apple TV
2. Plug in only power cable
3. Wait until stop blinking(Yes, it’s normal boot process), then connect Apple TV to your MAC
4.Run iPhone configuration utility and click summary tab
5. It’s over. You can see an UDID of your Apple TV :)