There is an easy way to disable the MacBook startup sound (boot chime) even after wiping out OS X and installing Linux.
This sound can be easily disabled if you mute the volume in OS X and shutdown the computer. The value is stored in NVRAM.
- Reboot the computer and hold Cmd+Alt(Option)+R. This will start OS X Internet recovery mode;
Open the terminal and issue the following command
Voila. In Linux try this:
# efivar -l | grep SystemAudioVolume 7c436110-ab2a-4bbb-a880-fe41995c9f82-SystemAudioVolume 7c436110-ab2a-4bbb-a880-fe41995c9f82-SystemAudioVolumeDB # efivar -n 7c436110-ab2a-4bbb-a880-fe41995c9f82-SystemAudioVolume -p GUID: 7c436110-ab2a-4bbb-a880-fe41995c9f82 Name: "SystemAudioVolume" Attributes: Non-Volatile Boot Service Access Runtime Service Access Value: 00000000 00 |. | # efivar -n 7c436110-ab2a-4bbb-a880-fe41995c9f82-SystemAudioVolumeDB -p GUID: 7c436110-ab2a-4bbb-a880-fe41995c9f82 Name: "SystemAudioVolumeDB" Attributes: Non-Volatile Boot Service Access Runtime Service Access Value: 00000000 00 #
Note 1: Before disabling both variables had non zero values. Also SystemAudioVolumeDB doesn't seem to have any effect.
Note 2: RHEL or CentOS users need to rebuild efivar from the Fedora src.rpm.
Note 3: several Internet sources suggest that writing EFI variables from Linux may sometimes corrupt your Apple firmware. I didn't research this any further. If you happen to figure out how to successfully write to these variables under Linux please let everyone know in the comments (in case OS X recovery mode goes missing, you know).
Thanks to my reader Alexander, who gave me the hint in a previous blog post.