Once, you have started the NiFi and got the URL where the NiFi is running, you will be asked to provide the Username and the Password.
NiFi generates random credentials. To get the credentials, go to the
logs folder under the root directory where the NiFi is installed.
nifi-app log file. Search for the keyword generated username using Cntrl+F. There you will find the username and password.
Go to the URL where NiFi is running and enter the details.
Now, you are successfully logged in.