Install the JDK

You should install JDK on each machine on which you will install NiFi, if your version of Cloudera Manager is not already configured with JDK.

The following Java versions are supported:

Download JDK from the appropriate website.
Run the installation command appropriate for your operating system:
For RHEL/CentOS:
```
yum install java-1.8.0-openjdk-devel
```

Once you have installed the JDK, ensure that you have the required database installed and set up for NiFi Registry.