This should be an option that’s available through the Finder preferences, but it’s not. Odd. Anyway, here’s how to do it. Open up a shell and run the following command:
defaults write com.apple.Finder AppleShowAllFiles YES
defaults write com.apple.Finder AppleShowAllFiles NO
To check to see if the option is set:
defaults read com.apple.Finder AppleShowAllFiles
To see the settings above take effect, you’ll need to hold the alt key and right-click on the Finder icon on your dock then click on Relaunch.