OSX-Optimizer
Optimize MacOS, Shell scripts to speed up your mac boot time
...The README emphasizes that macOS can be heavily modified using the defaults command, and many of the optimizations are simply well-chosen combinations of defaults and system utilities. It shows how to capture and compare system preferences before and after GUI changes (using defaults read and diff) so that users can understand which keys to automate. The script collection includes aggressive adjustments like skipping the GUI login screen, enabling performance mode via NVRAM flags, and disabling large wallpapers and visual effects to reduce graphical overhead. It also provides commands to disable Spotlight indexing system-wide, which can significantly speed up virtual machines where disk I/O is at a premium.