Auto boot in 64 bit mode (Snow Leopard)
Method 2: On-disk setting (persistent)
To select the 64-bit kernel for the current startup disk, use the following command in Terminal:
$ sudo systemsetup -setkernelbootarchitecture x86_64
To select the 32-bit kernel for the current startup disk, use the following command in Terminal:
sudo systemsetup -setkernelbootarchitecture i386
Note: This setting is stored in the /Library/Preferences/SystemConfiguration/com.apple.Boot.plist file and will take effect every time you start up from this disk. If you start up from a different disk, the setting on that disk, or the hardware default, will take effect.
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