Linux hide user from login screen

Set uid of the user (you want to hide) to any number which is less than 1000.

Example: change user www id to 999

usermod -u 999 www

for usermod see also http://www.cyberciti.biz/faq/howto-change-rename-user-name-id/

# rename username `old` => `new`
killall -u old
id old
usermod -l new old
groupmod -n new old
usermod -d /home/new -m new
usermod -c “New Real Name” new
id new