@Robin Dong In Linux only iptables controls the Kernel based firewall. You might have firewalld in CentOS7 or ufw in Ubuntu but they're just an abstraction layer on top of iptables. So if 'iptables -L' doesn't show anything then it's all good. The Ambari iptables check is rudimentary and it doesn't know if the rules that exist still allow all the traffic. It only checks for 'service iptables status' or 'systemctl status firewalld', which means there are no filter tables. But please be aware of the cloud firewall as well. For example in AWS even instances in the same Security Group are not allowed by default to communicate with each another and this must be enabled explicitly: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/security-group-rules-reference.html#sg-rules-other-instances ... View more

Q1. Change data capture in Ni-Fi is the easiest way to capture incremental records there are work around as well depending upon the use case. Q2. I believe yes. But if your target is hive then its better not go with all three. Capture just the incremental records into HDFS and do the comparison within HDFS and update the target. Q4. It depends. If you are looking for real-time processing then dont think of choosing sqoop. Sqoop is specifically desinged for large data processing. So if real- time processing is needed go with kafka/Nifi to ingest data into hadoop. Kafka/NiFi can handle incremental volume in a decent way. ... View more