I have tried to install magento2 in ubuntu 16.04 machine. I have followed these steps for install magento. When install composer then show these problems
- The requested PHP extension ext-gd * is missing from your system. Install or enable PHP's gd extension.
- The requested PHP extension ext-mcrypt * is missing from your system. Inst all or enable PHP's mcrypt extension.
Try these command in your shell
sudo apt-get install php7.0-gd sudo apt-get install php7.0-ext-mcrypt
then try again install composer