The command rbenv install is missing

In `Ubuntu 10.04` I just installed `rbenv`. The install command is not present. rbenv 0.4.0-49-g8b04303 Usage: rbenv <command> [<args>] Some useful rbenv commands are: commands List all available rbenv commands local Set or show the local application-specific Ruby version global Set or show the global Ruby version shell Set or show the shell-specific Ruby version rehash Rehash rbenv shims (run this after installing executables) version Show the current Ruby version and its origin versions List all Ruby versions available to rbenv which Display the full path to an executable whence List all Ruby versions that contain the given executable See `rbenv help <command>' for information on a specific command. For full documentation, see: https://github.com/sstephenson/rbenv#readme What am I missing?