Affects Version/s: None
Fix Version/s: 1.10.0
NIFI-6653 introduced a way to avoid the port being changed to prevent a possible hijacking of that port to provide other commands than those explicitly between bootstrap and the nifi process. This causes issues when the NiFi process dies and precludes restart (the default functionality enabled out of the box).
To recreate, build/run NiFi off of current master and kill the NiFi process.
This will result in the following (when an additional nifi.sh status is carried out).
2019-09-25 17:10:55,601 WARN [main] org.apache.nifi.bootstrap.RunNiFi Apache NiFi appears to have died. Restarting...
2019-09-25 17:10:55,620 INFO [main] org.apache.nifi.bootstrap.Command Launched Apache NiFi with Process ID 2088
2019-09-25 17:10:55,621 INFO [main] org.apache.nifi.bootstrap.RunNiFi Successfully started Apache NiFi with PID 2088
2019-09-25 17:10:56,174 WARN [NiFi Bootstrap Command Listener] org.apache.nifi.bootstrap.RunNiFi Blocking attempt to change NiFi command port and secret after they have already been initialized. requestedPort=37871
2019-09-25 17:11:50,783 INFO [main] o.a.n.b.NotificationServiceManager Successfully loaded the following 0 services: 
2019-09-25 17:11:50,785 INFO [main] org.apache.nifi.bootstrap.RunNiFi Registered no Notification Services for Notification Type NIFI_STARTED
2019-09-25 17:11:50,786 INFO [main] org.apache.nifi.bootstrap.RunNiFi Registered no Notification Services for Notification Type NIFI_STOPPED
2019-09-25 17:11:50,786 INFO [main] org.apache.nifi.bootstrap.RunNiFi Registered no Notification Services for Notification Type NIFI_DIED
2019-09-25 17:11:50,809 INFO [main] org.apache.nifi.bootstrap.Command Apache NiFi is running at PID 2088 but is not responding to ping requests