Backup Minecraft Virtual Worlds
Before you install Forge or Mods be sure to backup your Minecraft worlds first.
Steps to backup your Minecraft files.
1. cd /Users/$USER/Library/Application\ Support/minecraft/
2. tar -czf /tmp/Minecraft-worlds.tar.gz ./mods/ ./saves/ ./screenshots/ ./launcher_profiles.json ./options.txt
Here's a description of what each folder contains. Folders in bold are user generated.
/assets/ Contains game assets like icons, language packs, and sounds. If you want to listen to the Minecraft theme songs outside of the game you’ll find them in /music/game/
/libraries/ Contains Java libraries for handling audio/video rendering and other tasks.
/logs/ Contains debug/game logs. Useful for troubleshooting problems, but otherwise unimportant.
/resource packs/ Contains user-downloaded resource packs (which used to be called texture packs). Resource packs allow players to reskin the game with new textures and/or new sounds.
/screenshots/ Contains all in-game screenshots captured using the in-game screenshot tool (by default, activated with F2).
/saves/ Contains your Minecraft worlds. Each world has a unique directory based on its name (e.g. /New World/, /Wizard Land/, etc.)
/versions/ Contains your current and (potentially) past versions of Minecraft organized via version-numbered sub-directories.
/launcher_profiles.json Database file; contains all the relevant information about your individual profiles including the default profile.
/launcher.jar Archive of assets and game libraries.
/launcher.pack.lzma Auxiliary launcher-related file.
/options.txt Text file containing all the user-configurable in-game options like mouse sensitivity, chat options, and key bindings.