The Advanced Package Tool, or APT, is a free software user interface that works with core libraries to handle the installation and removal of software on the Debian Linux distribution and its variants. APT simplifies the process of managing software on Unix-like computer systems by automating the retrieval, configuration and installation of software packages, either from precompiled files or by compiling source code. Wikipedia
root@ubilinux:~# apt-get update && sudo apt-get upgrade
root@ubilinux:~# apt-get install git-core
root@ubilinux:~# apt-get install ca-certificates