Launchpad will not create a .db file in ~/Library/Application Support/Dock to save the state of Launchpad.
It always resets to default upon restart. I have tried many terminal commands, the most recent being:
rm ~/Library/Application\ Support/Dock/*.db ; killall Dock
defaults write com.apple.dock ResetLaunchPad -bool true; killall Dock
How can I force Launchpad to create this file?