sudo -H -u username bash -c 'echo "Hello. I am $USER"'

dd if=/dev/zero of=/swapfile bs=1014 count=4194304; chown root:root /swapfile; chmod 0600 /swapfile; mkswap /swapfile; swapon /swapfile;
echo 'swapon /swapfile' >> /etc/rc.local; chmod +x /etc/rc.d/rc.local; ls -alh /etc/rc.d/rc.local; tail -n 3 /etc/rc.d/rc.local; free -m