A recently installed application writes log data to /opt/app/log/info.

The correct answer to the question "What has to be done in order to submit the log data of the new application to Logstash?" is:

C. Add the log file to the path option within the log prospector in the Filebeat configuration and restart Filebeat.

To configure Filebeat to submit log data from a new application log file, you need to update the Filebeat configuration to include the path to the new log file and then restart Filebeat.

C. Add the log file to the path option within the log prospector in the Filebeat configuration and restart Filebeat: This involves editing the Filebeat configuration file to include the new log file path under the input section and then restarting the Filebeat service to apply the changes.

The other options are incorrect:

A: Logstash configuration should not be directly modified for this purpose; it is handled by Filebeat.

B: Logrotate is not involved in Filebeat's log shipping process.

D: There is no need to create a cron job for this purpose.

E: Using symbolic links to /dev/filebeat is not a standard or recommended approach.

References:

Filebeat Documentation - Configuration