My vm host system is UBUNTU 18.04, I did the following to fix the problem: 1. vi /etc/cloudera-scm-agent/config.ini     server_host = (my master host's ip address) 2. run: getenforce, if the result is disabled, the go ahead, otherwise run: setenforce=0 3. disable firewalls     systemctl stop  firewalld     systemctl disable  firewalld       systemctl ufw firewalld     systemctl ufw firewalld    4. check if networking service is running, if not, start it:     systemctl start networking  (or run /etc/init.d/networking start)   Good luck! ... View more