每次使用iTunes对iPhone或iPad进行同步时，总会自动备份文件，一来耗费了大量的时间，二来备份文件只能按默认储存在C盘，这对很多朋友来说是非常悲催的事情。然而，关闭iTunes不能通过常规方法，只能通过修改其配置文件来达成，下面简要介绍一下Mac平台和Win平台的操作方法。

• Mac

1. Close iTunes on your Mac.
   1. Launch Terminal.
   2. Type
      defaults write com.apple.iTunes DeviceBackupsDisabled -bool true
      and press Enter.
   3. If you want to re-enable automatic backups, type
      defaults write com.apple.iTunes DeviceBackupsDisabled -bool false
      and press Enter.

• Win

1. Close out of the iTunes application.
   1. Hold the Windows Key and press “R” to bring up the Run dialog box.
   2. Type the following depending on whether you have 32 or 64 -bit windows:
      64-bit: "C:\Program Files\iTunes\iTunes.exe" /setPrefInt AutomaticDeviceBackupsDisabled 1 then press “Enter“.
      32-bit: "C:\Program Files (x86)\iTunes\iTunes.exe" /setPrefInt AutomaticDeviceBackupsDisabled 1
      then press “Enter“.
   3. If you wish to enable backups again, use the same command as above, but replace the 1 with a 0.

Reference:

https://discussions.apple.com/message/27288977

http://www.technipages.com/disable-iphone-ipad-or-ipod-touch-backup-process