How to safely remove drush via pear and then install via composer?
Uninstalling Drush using Pear

If Drush has been installed using Pear, it can be removed using the following command.

pear uninstall drush/drush


Installing Drush via Composer

For the most current install instructions, refer to the Drush GitHub page.

1) Add Composer's global bin directory to the system PATH (recommended):

sed -i '1i export PATH="$HOME/.composer/vendor/bin:$PATH"' $HOME/.bashrc
source $HOME/.bashrc


2) Install Drush

composer global require drush/drush