CoreOS choose release channel alpha and update

coreos.sh

#!/bin/bash
echo "GROUP=alpha" > /etc/coreos/update.conf # This is not good idea because of unstable updates, so risky for production
sudo systemctl restart update-engine
update_engine_client -check_for_update
# for checking os version after restarting
cat /etc/os-release
# source from https://coreos.com/os/docs/latest/switching-channels.html