sudo apt-get install git
は罠
gitで入るのは
git (GNU Interactive Tools) is a set of interactive text-mode tools, closely integrated with the shell.
sudo apt-get install git-core
が正解
http://wiki.cureblack.com/?ubuntu%A4%C7git%A5%A4%A5%F3%A5%B9%A5%C8%A1%BC%A5%EB