we can download magento2 in 3 ways.
1) Direct Download
2) Using COMPOSER
3) Using GIT
Step1: go to your root folder and check git install on
your local machine or not. type below command on console.
git
If not than install it.
apt -get install git
Step2: get a git clone on the root directory.
git clone https://github.com/magento/magento2.git
Step3: Give the permission of the folder
sudo chmod -R 777 YOUR-PROJET-FOLDER-NAME/
Step4: After that put below url on your local browser.
http://localhost/YOUR-PROJET-FOLDER-NAME/