sudo /usr/sbin/nvram boot-args="-v"

http://www.oreillynet.com/pub/h/348

[quote]
Verbose booting shows you the actual process of Mac OS X's startup. You'll see drivers get loaded and services launch. This command should work on any recent (New World) Macintosh: sudo /usr/sbin/nvram boot-args="-v". The -v flag tells the system to boot verbosely. You can get the same result by holding Command + V at boot time, but that will only work the one time. Modifying the boot-args will cause Mac OS X to always boot verbosely from now on... To resume normal booting, use the command sudo /usr/sbin/nvram boot-args="".
[/quote]

nvram (Verbose Mac OS startup)

Bash, osx

Bash