MacOS の起動音を消す方法

GUI から設定

「システム設定」-「サウンド」から変更

ターミナルから設定

Off にする場合

sudo nvram StartupMute=%01

On にする場合

sudo nvram StartupMute=%00

nvram は NVRAM の内容を操作するコマンド

% nvram -h
nvram: (usage: )
nvram [-x|-X] [-p] [-f filename] [-d name] [-c] name[=value] ...
    -x         use XML format for printing or reading variables
               (must appear before -p or -f)
    -X         use HEX format for printing or reading variables
               (must appear before -p or -f)
    -p         print all firmware variables
    -f         set firmware variables from a text file
    -d         delete the named variable(does not return error code)
    -r         delete the named variable(returns error code if any)
    -c         delete all variables
    -b         set variable using binary file. invoked with the following format: nvram -b <variable name> <binary file>
    name=value set named variable
    name       print variable
Note that arguments and options are executed in order.