Disabling startup sound/chime on the MacBook

Today at university, a fellow student asked me about how I disabled the startup chime/sound that the MacBook makes when it is powered on from cold state. I remembered I applied some setting after a suggestion on the mactel-linux-users mailing list, but I didn't remember exactly how I did it. Just in case, I need to repeat this procedure, and to tell him what worked for me, I started looking for the corresponding post. Here it is: how to silence apple startup chime.

Good thing that OS X is based on BSD, and therefore very unix-y, we can simply edit the local shutdown script (/etc/rc.shutdown.local) and append the following line:

/usr/sbin/nvram SystemAudioVolume=%80

This will set the volume in nvram to zero and effectively disable the startup chime, so you won't be annoyed by the startup chime when you forgot to mute the OS X audio volume before shutdown. The good thing with this method is that you don't need to install nasty third-party software, and that it still preserves the volume settings inside Mac OS X and (of course) in Linux, thanks to alsactl's restore functionality.