drush installation instructions here:
#Type the following commands into terminal for drush 8.3.2 installation
cd /home/`whoami` #or cd ~
composer require drush/drush 8.3.2
a folder called vendor/bin/drush will be created , put this in a location such as /home/`whoami`
# When you need to be able to run a Linux tool from a non-standard directory, you need to add that directory to your user $PATH. # Here's how to do it.
nano ~/.bashrc #or vi ~/.bashrc
#when the bashrc terminal opens type in the following
export PATH=$PATH:/home/`whoami`/vendor/drush/drush
#"username" is your own username. For instance, if your username is "Alex," type in "Alex," for username. or just use `whoami`
#To testout if the application is in your $PATH, type in "echo $PATH," in your terminal. Your terminal shoukd return something like "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/home/username/vendor/drush/drush"
# To test if drush is installed, type in "drush," and its commands should show up.
drush --version # this should give you 8.3.2