I researched how to check the kernel bit count and how to switch between 32bit and 64bit on Mac OS X Lion, so here’s a memo.

■ How to check kernel bit count

$ getconf LONG_BIT

It will display 64 for 64bit and 32 for 32bit.

■ How to switch between 32bit and 64bit kernel

・Set 64-bit kernel as default (restart after execution)

$ sudo systemsetup -setkernelbootarchitecture x86_64

・Set 32-bit kernel as default (restart after execution)

$ sudo systemsetup -setkernelbootarchitecture i386

That’s all.

【Reference】

・Mac OS X Lionのカーネルは64ビット：脈絡もとりとめもない独り言：So-netブログ

・Macの旧モデルユーザーは知っておきたい「systemsetup」コマンド - builder

That’s all from the Gemba.